Health Reports
All-cause acute care hospitalization rates of immigrants and the Canadian-born population: A linkage study

by Edward Ng, Jacklyn Quinlan, George Giovinazzo, Anne Grundy, Claudia Rank, Maria Syoufi, David Ponka, and Rochelle Garner

Release date: September 15, 2021

DOI: https://www.doi.org/10.25318/82-003-x202101000001-eng

Abstract

Background

As Canadian immigration levels increase, knowledge concerning immigrant health becomes increasingly important for health system policy and planning. This study compares the rate of all-cause hospitalization among immigrants with that of their Canadian-born counterparts.

Data and methods

Using records from the Discharge Abstract Database (2004/2005 to 2016/2017) and the Ontario Mental Health Reporting System (2006/2007 to 2017/2018) linked to the 2016 Longitudinal Immigration Database, this study compared the age-standardized hospitalization rates (ASHRs) among immigrants with those of the Canadian-born population; the latter were obtained from a linkage based on the 2011 National Household Survey. Comparisons were made at the International Classification of Diseases chapter level by immigrant landing year, admission category and world region of birth. Quebec data were not available.

Results

Overall, ASHRs among immigrants were lower than for the Canadian-born population. Immigrants in the economic class had the lowest ASHR, followed by those in the family class and among refugees. After pregnancy was excluded, leading hospitalization causes were similar for immigrants and the Canadian-born population, where top causes included digestive system and circulatory diseases, injuries, and cancer. In male and female immigrants, the ASHRs were lowest among those from East Asia. By landing year, males arriving earlier had the highest ASHR compared with the most recent arrivals. When pregnancy was excluded and while the differential in ASHRs among females by landing year remained, the magnitude was smaller.

Interpretation

These results corroborate those from previous studies suggesting a healthy immigrant effect, but also reveal heterogeneity in ASHRs within the immigrant population. They provide a baseline for comparison of health status between populations, which enables further monitoring and informs health-system policy and planning.

Keywords

Immigrant health, immigrant admission characteristics, hospitalization, data linkage, disease classification

Authors

Edward Ng (Edward.ng@canada.ca) and Rochelle Garner are with the Health Analysis Division, Statistics Canada. Jacklyn Quinlan, George Giovinazzo, Anne Grundy, Claudia Rank, and Maria Syoufi are with the Migration Health Branch, Immigration, Refugees and Citizenship Canada. David Ponka is with the Department of Family Medicine, University of Ottawa.

 

What is already known on this subject?

  • Previous studies have observed a healthy immigrant effect, where immigrants typically arrive in good health, compared with their Canadian-born counterparts, but their health status declines over time. Furthermore, health status has been associated with immigrant admission characteristics and world region of origin.
  • Using the Longitudinal Immigration Database linked to hospitalization data (excluding Quebec), previous studies had analyzed leading causes of hospitalization among immigrants to Canada by immigrant-related covariates. However, these earlier studies did not compare hospitalization rates between immigrants and the Canadian-born population, and there is a need to incorporate previously missing mental health data from Ontario with these comparisons.

What does this study add?

  • While the results suggest a healthy immigrant effect, heterogeneity in hospitalization rates within the immigrant population is observed. The overall age-standardized hospitalization rates (ASHRs) among immigrants were lower than those of the Canadian-born population. Among immigrants, ASHRs were lowest in the economic class, followed by the family class and among refugees. The ASHRs were lowest among immigrants from East Asia.
  • By landing year, males arriving earlier had the highest ASHR, compared with the most recent arrivals. Excluding pregnancy, a similar but weaker differential in ASHRs among females by landing year was observed. While differences in the leading causes of hospitalization exist between sex, circulatory disorders and digestive disorders ranked highly and were similar for immigrants and the Canadian-born population. Mental health ranked as the fifth and sixth leading causes of hospitalization among males and females (excluding pregnancy), respectively.
  • Increased understanding of both the patterns and the determinants of immigrant health outcomes supports health policy making and improving continuity of care and settlement in Canada.

Introduction

In 2019, approximately 340,000 immigrants became permanent residents in Canada, with the numbers expected to reach more than 400,000 per year by 2023.Note 1 The Canadian government accords high priority to the health of immigrants, given the importance of health in successful integration and economic productivity. As part of Immigration, Refugees and Citizenship Canada’s (IRCC) health screening requirements, all permanent residence applicants must undergo an immigration medical examination. For admissibility purposes, Canada medically screens immigrants for selected diseases that pose a threat to public health (e.g., tuberculosis) or public safety, as well as to mitigate the impact on Canadian health or social services.Note 2

Research on the health status of immigrants and their utilization of health services is instrumental for health policy and strategic health care planning. Previous studies have described a healthy immigrant effect (HIE) in this population; immigrants typically arrive in good health compared with their Canadian-born counterparts, but their health status declines over time.Note 3Note 4Note 5Note 6Note 7Note 8Note 9 Furthermore, health status has been associated with immigrant admission characteristics and world region of origin.Note 10

Data on hospitalization can serve as an indicator of health among immigrants. Using immigrant landing administrative data linked to health care data, leading causes of hospitalization can be assessed in a large cohort that also allows for the analysis of immigrant-related covariates. This approach was used in an earlier study based on immigration and health care datasets from 2006 to 2008.Note 11 However, this previous study did not directly compare hospitalization rates between immigrants and the Canadian-born population, and it did not incorporate mental health data from Ontario.Note 11 In light of increasing Canadian immigration levels,Note 1 an updated analysis of hospitalization patterns among immigrants to Canada, relative to the Canadian-born population, is needed to inform health care system policy and planning. This descriptive study aims to examine hospitalization rates and leading causes of hospitalization, including mental health in immigrants and the Canadian-born population, stratified by sex and selected immigration characteristics

Data and methods

Data linkage

Similar to previous work,Note 12 the Longitudinal Immigration Database (IMDB) was linked to the hospital Discharge Abstract Database (DAD) at Statistics Canada (StatCan) using the Social Data Linkage Environment (SDLE) and its highly secured central depository called the Derived Record Depository (DRD).Note 13 In addition, discharge-related records from the Ontario Mental Health Reporting System (OMHRS) were also linked in the SDLE to account for discharges from mental health institutions and psychiatric facilities in the province of Ontario, which have been captured solely in the OMHRS (and not in the DAD) since fiscal year 2006/2007. Mental health hospitalizations from all other provinces were included in the DAD. Also, the 2011 Canadian Census Health and Environment Cohort (CanCHEC) provided the Canadian-born comparison group for the IMDB-based results. These linkages were approved by StatCan’s senior management,Note 14 and use of the de-identified linked data is governed by the Directive on Record Linkage.Note 15

The IMDB is a research database representing unduplicated immigrant records derived from the Immigrant Landing File. The IMDB contains administrative information for all individuals who have landed in Canada since 1980, with data provided to StatCan monthly by IRCC.Note 16 In the present study, landing records and temporary resident permits from 1980 to 2017 were eligible for linkage (n=12,317,708). Using probabilistic methods, the IMDB was linked to the DRD (linkage rate of 90%, n=11,036,264).Note 17

The DAD contains demographic, administrative and clinical data for all acute-care and some psychiatric, chronic rehabilitation and day-surgery discharges for all provinces and territories, excluding Quebec.Note 18 Data are provided to StatCan annually by the Canadian Institute for Health Information (CIHI) for each fiscal year. Hospital discharges that occurred between April 1, 1994, and March 31, 2017, were eligible for linkage from 84.8 million hospital discharge records. The linkage used a deterministic approach, yielding a linkage rate of 91%.Note 19

The OMHRS is a CIHI database that includes information about all individuals admitted to designated inpatient mental health beds in general and specialty facilities in Ontario since 2006/2007.Note 20 CIHI provides OMHRS data to StatCan annually. The OMHRS includes information at the assessment level about patients’ mental and physical health, social supports, and service use. Mental health assessment records covering the period from April 1, 2006, to March 31, 2018, were eligible for linkage to the DRD in the present study (n=1,248,844). The linkage used a deterministic approach (linkage rate of 82.7%).Note 21

Finally, the 2011 CanCHEC, a population-based study cohort based on the 2011 National Household Survey (NHS), was probabilistically linked with the DADNote 22 and the OMHRS through the SDLE. Together these linkages provide the corresponding hospitalization data among the Canadian-born cohort (the 2011 NHS-DAD-OMHRS linked data), while the IMDB was linked to hospitalization data for the immigrant  cohort (the 1980 IMDB-DAD-OMHRS linked database). The NHS was probabilistically linked to the DRD with a linkage rate of 96.7% (n=6,499,185).Note 22

Study cohorts

The present study included two cohorts: an immigrant cohort and a Canadian-born cohort. The immigrant cohort was based on the IMDB and was limited to immigrants who arrived in Canada between January 1, 1980, and May 10, 2011. Immigrants in this study were limited to permanent residents, so temporary residents (e.g., students, workers, visitors) were excluded. Permanent residents include both economic and family-class immigrants, as well as refugees. Immigrants with a death recorded as occurring prior to May 10, 2011, on the IMDB (as per a previous linkage with the Canadian Vital Statistics Death Database) were removed from the IMDB immigrant study cohort.

In contrast to previous linkages that merged the IMDB with hospital discharges through the 2006 Census, which has been previously linked to both databases independently,Note 23 the current linkage did not use such a bridge file, making it susceptible to including immigrants who were no longer in Canada after landing. Without the removal of these emigrants from the analysis, the derived hospitalization rates would be underestimated. In the present study, tax files that are part of the IMDB were used as a proxy for emigration. Individuals who did not file taxes in both 2010 and 2011 were assumed to have emigrated. The exceptions were new immigrants who arrived during those two years, as well as children and youth younger than 19 (as of May 10, 2011), who may not have needed to file taxes. This resulted in 17% of male and 18% of female IMDB immigrants being identified as emigrants and, therefore, excluded from the study cohort. Lastly, to account for the fact that Quebec does not contribute data to the DAD, immigrants to Quebec were removed from the cohort. The final number of individuals in the immigrant cohort was 4,162,005.

The Canadian-born cohort was composed of respondents in the 2011 CanCHEC who self-identified as being Canadian-born. To account for the fact that Quebec does not contribute data to the DAD, 2011 CanCHEC members who resided in Quebec were excluded from the analysis. The final sample size of the Canadian-born cohort was 3,754,230, representing a weighted population of 19,037,385.

Hospitalization records from the DAD and the OMHRS were linked to the immigrant and Canadian-born cohorts for a five-year follow-up period, starting from Census Day 2011 (May 10, 2011) through to May 9, 2016. Hospitalization rates for immigrants arriving between 1980 and 2011 based on the NHSDAD and the NHSOMHRS were compared with the rates based on the IMDBDAD and the IMDBOMHRS for the same period to validate the use of tax filing patterns as a proxy for emigration. They were found to be similar (data not shown).

Hospital discharges by cause

The primary outcome measure in this study was an acute-care hospital discharge occurring during the five-year study period. Discharges were classified according to the diagnosis or condition most responsible for the patient’s stay in hospital.Note 24 Diagnoses were coded using the 10th edition of the International Classification of Diseases and Related Health Problems, Canada (ICD-10-CA), and these were subdivided according to their chapter code. As the OMHRS employs a mental health disease classification system other than ICD-10-CA, all OMHRS records that were linked to the study cohorts were classified as Chapter 5, i.e., mental and behavioural disorders. Hospitalizations related to pregnancy were considered as discharges with a most responsible diagnosis in Chapter 19 of ICD-10-CA, or those coded as Z34-Z39, which include supervision of normal and high-risk delivery, and postpartum care and examination. To avoid overestimation of discharges related to hospital transfers, hospital admissions within one day of a previous discharge for the same patient were consolidated into a single hospitalization episode. In these cases, the most responsible diagnosis for the last hospital discharge within the episode was used to characterize the nature of the hospitalization.

Stratification variables

Age and sex were determined for the immigrant cohort and the Canadian-born cohort based on the IMDB and the CanCHEC, respectively. For the Canadian-born cohort, age was calculated as of May 10, 2011. Among immigrants, age was calculated as the difference between 2011 and the birth year obtained from the IMDB. Age was subsequently grouped as 0 to 17, 18 to 39, 40 to 64, and 65 and older.

Immigrant characteristics, including landing year, country of birth and admission class, were obtained from the IMDB. Landing year was grouped as 1980 to 1989, 1990 to 2002 and 2003 to 2011 to align with corresponding changes in immigration policy.Note 25 Immigrant birth countries were grouped into 10 world regions: the United States, the Caribbean and Central and South America, Western Europe, Eastern Europe, Sub-Saharan Africa, Southwest Asia and North Africa, South Asia, Southeast Asia, East Asia, and others. Immigrant admission classes were classified into four general groups: economic class (including principal applicants, and spouses and dependants), family class (subdivided into parents and grandparents, and spouses and dependants), refugees (composed of resettled refugees and protected persons) and others. Resettled refugees were further classified as government assisted, privately sponsored and dependants; protected persons include in-Canada protected persons and their dependants.

Statistical methods

Descriptive statistics are presented to characterize the immigrant and Canadian-born cohorts. Crude rates and age-standardized hospitalization rates (ASHRs) were derived by sex for overall hospitalization (with and without pregnancy) and for the top four leading causes (ranked by distribution, excluding pregnancy for women). These rates were also stratified by the variables identified above (immigrant admission class, landing year and world region). The Canadian-born population (excluding Quebec) from the 2011 NHS was used as the reference population for standardization. Rate derivation was adjusted for individuals who died during follow-up. Lastly, to account for the 2011 NHS complex survey design and to adjust for linkage, estimates for the Canadian-born cohort were calculated using sample and bootstrap weights to account for complex survey design.Note 22 No weighting adjustment was used for the immigrant cohort, as the cohort is considered to be a census of immigrants.

Results

The characteristics of the immigrant and Canadian-born populations are shown in Table 1, with immigrants comprising 18% of the overall weighted study cohort. Almost half of the immigrants in the study cohort were aged 40 to 64 years, and almost half arrived in Canada between 1990 and 2002. More than half of immigrants were from South, Southeast and East Asia, with the top source countries being China, India and the Philippines (detailed country-level data not shown). The highest percentage of immigrants were admitted as economic-class applicants, followed by the family class.


Table 1
Descriptive characteristics of the study cohort, separately for the Canadian-born population and immigrant cohort, by sex
Table summary
This table displays the results of Descriptive characteristics of the study cohort Canadian-born population
(weighted), IMDB immigrant cohort
(1980 to 2011) , Males (n=9,456,690), Females (n=9,580,695) , Males (n=1,990,725) and Females (n=2,171,280), calculated using percent units of measure (appearing as column headers).
Canadian-born population
(weighted)
IMDB immigrant cohort
(1980 to 2011)
Males (n=9,456,690) Females (n=9,580,695) Males (n=1,990,725) Females (n=2,171,280)
percent
Age groups
0 to 17 26.6 24.7 10.7 9.3
18 to 39 29.5 28.7 35.4 37.1
40 to 64 33.2 34.0 46.2 44.5
65 and older 10.8 12.6 7.6 9.1
Immigration landing year
1980 to 1989 Note ...: not applicable Note ...: not applicable 16.9 16.4
1990 to 2002 Note ...: not applicable Note ...: not applicable 45.6 45.9
2003 to 2011 Note ...: not applicable Note ...: not applicable 37.5 37.6
Source world region
United States Note ...: not applicable Note ...: not applicable 2.6 2.9
The Caribbean and Central and South America Note ...: not applicable Note ...: not applicable 9.8 10.5
Western Europe Note ...: not applicable Note ...: not applicable 7.5 6.6
Eastern Europe Note ...: not applicable Note ...: not applicable 10.6 10.8
Sub-Saharan Africa Note ...: not applicable Note ...: not applicable 5.5 5.1
Southwest Asia, Middle East and North Africa Note ...: not applicable Note ...: not applicable 10.9 9.1
South Asia Note ...: not applicable Note ...: not applicable 23.2 21.8
Southeast Asia Note ...: not applicable Note ...: not applicable 8.9 11.0
East Asia Note ...: not applicable Note ...: not applicable 19.9 21.3
Others Note ...: not applicable Note ...: not applicable 1.2 1.1
Immigrant admission category
Economic Note ...: not applicable Note ...: not applicable 53.9 48.8
Principal applicants Note ...: not applicable Note ...: not applicable 28.3 13.5
Spouse and dependants Note ...: not applicable Note ...: not applicable 25.6 35.2
Family Note ...: not applicable Note ...: not applicable 28.2 37.5
Parents and grandparents Note ...: not applicable Note ...: not applicable 9.2 11.1
Spouse and dependants Note ...: not applicable Note ...: not applicable 18.3 25.7
Refugee Note ...: not applicable Note ...: not applicable 16.7 12.5
Resettled
Government assisted Note ...: not applicable Note ...: not applicable 3.6 1.1
Privately sponsored Note ...: not applicable Note ...: not applicable 3.4 1.2
Dependants of resettled refugees Note ...: not applicable Note ...: not applicable 3.9 5.7
Protected persons
In-Canada refugees Note ...: not applicable Note ...: not applicable 4.6 3.3
Dependants of protected persons Note ...: not applicable Note ...: not applicable 1.1 1.2
Others Note ...: not applicable Note ...: not applicable 1.3 1.3

Table 2 shows the distribution of hospital events classified by ICD-10-CA chapters among immigrants, compared with the Canadian-born cohort, stratified by sex, with and without pregnancy-related discharges. The highest percentages of hospital events among immigrant males were for circulatory conditions (17%), digestive disorders (15%), injuries (9%), and neoplasms (9%); as a whole, they contributed to 50% of all hospitalizations among these males. This ranking was similar for Canadian-born males, with the exception of respiratory diseases (10%), which ranked fourth in the Canadian-born cohort. For female immigrants, the highest percentages of hospital events, excluding pregnancies and childbirth, were neoplasms (14%), digestive disorders (13%), circulatory conditions (11%) and genitourinary conditions (10%), which together comprised close to 50% of all hospitalizations among females, excluding pregnancy. The ranking of health conditions for Canadian-born females was slightly different, with digestive disorders (13%), circulatory conditions (11%), injuries (9%) and musculoskeletal disorders (9%) ranked as the top four conditions for hospitalization. Combined, these conditions accounted for 42% of all Canadian-born female hospitalizations, excluding pregnancy. Pregnancy accounted for 43% of all female hospitalizations among immigrants, compared with 23% among Canadian-born females.


Table 2
Hospitalization events from May 10, 2011, to May 9, 2016, by ICD-10-CA chapter among IMDB immigrants (1980 to 2011) compared with NHS Canadian-born (excluding Quebec)
Table summary
This table displays the results of Hospitalization events from May 10. The information is grouped by ICD-10-CA chapters (appearing as row headers), NHS, IMDB , Canadian-born population (weighted), IMDB immigrants (landing 1980 to 2011), Males
(n=2,765,450), Females (n=3,867,455), Females, excluding pregnancy and childbirth (n=2,906,850), Males
(n=328,215), Females (n=643,050) and Females, excluding pregnancy and childbirth (n=350,320) (appearing as column headers).
ICD-10-CA chapters NHS IMDB
Canadian-born population (weighted) IMDB immigrants (landing 1980 to 2011)
Males
(n=2,765,450)
Females (n=3,867,455) Females, excluding pregnancy and childbirth (n=2,906,850) Males
(n=328,215)
Females (n=643,050) Females, excluding pregnancy and childbirth (n=350,320)
Percent Rank Percent Rank Percent Rank Percent Rank Percent Rank Percent Rank
I - Infectious/parasitic 2.8 Note ...: not applicable 2.2 Note ...: not applicable 3.0 Note ...: not applicable 3.2 Note ...: not applicable 1.7 Note ...: not applicable 3.1 Note ...: not applicable
II - Neoplasms 7.5 Note ...: not applicable 6.2 Note ...: not applicable 8.2 Note ...: not applicable 8.6 4 7.4 2 13.6 1
III - Blood and immune system 1.1 Note ...: not applicable 0.9 Note ...: not applicable 1.2 Note ...: not applicable 1.2 Note ...: not applicable 0.9 Note ...: not applicable 1.6 Note ...: not applicable
IV - Endocrine and metabolic 3.0 Note ...: not applicable 2.8 Note ...: not applicable 3.8 Note ...: not applicable 2.9 Note ...: not applicable 2.0 Note ...: not applicable 3.6 Note ...: not applicable
V - Mental 7.3 Note ...: not applicable 5.8 Note ...: not applicable 7.7 Note ...: not applicable 8.5 Note ...: not applicable 4.0 Note ...: not applicable 7.2 Note ...: not applicable
VI - Nervous 2.1 Note ...: not applicable 1.4 Note ...: not applicable 1.9 Note ...: not applicable 1.9 Note ...: not applicable 0.9 Note ...: not applicable 1.6 Note ...: not applicable
VII - Eye and adnexa 0.3 Note ...: not applicable 0.2 Note ...: not applicable 0.3 Note ...: not applicable 0.3 Note ...: not applicable 0.1 Note ...: not applicable 0.2 Note ...: not applicable
VIII - Ear and mastoid 0.3 Note ...: not applicable 0.2 Note ...: not applicable 0.3 Note ...: not applicable 0.3 Note ...: not applicable 0.2 Note ...: not applicable 0.4 Note ...: not applicable
IX - Circulatory 15.6 1 7.9 3 10.5 2 16.9 1 6.0 4 11.0 3
X - Respiratory 9.5 4 6.6 Note ...: not applicable 8.8 Note ...: not applicable 7.5 Note ...: not applicable 3.4 Note ...: not applicable 6.2 Note ...: not applicable
XI - Digestive 12.9 2 9.5 2 12.6 1 15.2 2 7.1 3 13.0 2
XII - Skin 1.3 Note ...: not applicable 0.9 Note ...: not applicable 1.1 Note ...: not applicable 0.8 Note ...: not applicable 0.4 Note ...: not applicable 0.7 Note ...: not applicable
XIII - Musculoskeletal 7.6 Note ...: not applicable 6.6 Note ...: not applicable 8.8 4 5.2 Note ...: not applicable 3.8 Note ...: not applicable 7.0 Note ...: not applicable
XIV - Genitourinary 5.3 Note ...: not applicable 6.4 Note ...: not applicable 8.5 Note ...: not applicable 6.7 Note ...: not applicable 5.4 Note ...: not applicable 9.9 4
XV - Childbirth 0.1Table 2 Note ‡‡ Note ...: not applicable 22.4 1 Note ...: not applicable 0.1Table 2 Note ‡‡ Note ...: not applicable 42.6 1 Note ...: not applicable
XVI - Perinatal 0.1Table 2 Note ‡‡ Note ...: not applicable 0.2 Note ...: not applicable 0.2 Note ...: not applicable 0.0Table 2 Note ‡‡ Note ...: not applicable 0.1 Note ...: not applicable 0.1 Note ...: not applicable
XVII - Congenital malformations 0.4 Note ...: not applicable 0.3 Note ...: not applicable 0.4 Note ...: not applicable 0.3 Note ...: not applicable 0.2 Note ...: not applicable 0.3 Note ...: not applicable
XVIII - Abnormal clinical and lab findings 6.6 Note ...: not applicable 5.5 Note ...: not applicable 7.2 Note ...: not applicable 6.9 Note ...: not applicable 3.9 Note ...: not applicable 7.2 Note ...: not applicable
XIX - Injury 9.8 3 7.0 4 9.3 3 8.9 3 4.3 Note ...: not applicable 7.9 Note ...: not applicable
XXI - Factors influencing health status contact and health services 6.6 Note ...: not applicable 6.8 Note ...: not applicable 6.4 Note ...: not applicable 4.9 Note ...: not applicable 5.8 Note ...: not applicable 5.2 Note ...: not applicable

Immigrants had almost half the overall crude rates and ASHRs of the Canadian-born population in both males and females when excluding pregnancy and childbirth (Table 3). The ASHR for Canadian-born males was 646 per 10,000 population (95% confidence interval [CI]=641 to 652), compared with 358 among immigrant males (95% CI=356 to 361). Similarly, the ASHR for Canadian-born females, excluding pregnancy, was 622 per 10,000 population (95% CI=617 to 627), compared with 331 among immigrant females (95% CI=329 to 333). The crude rates and ASHRs for immigrants were lowest in the economic class, followed by the family class and refugees for both males and females. The ASHRs were lowest for immigrants who landed in more recent years, and they increased with time spent in Canada to approach those of the Canadian-born population. For example, among males, the ASHR increased from 279 (95% CI=275 to 283) among those who landed between 2003 and 2011 to 400 (95% CI=396 to 405) among immigrants who landed between 1980 and 1989. For females, the effect of time since landing on the ASHR was observed only when pregnancy-related hospitalizations were excluded from ASHR calculations. For both males and females, the ASHR of immigrants was lowest among those from East Asia.


Table 3
Overall crude and age-standardized acute-care hospitalization ratesTable 3 Note †† (ASHRs, per 10,000 population) for IMDB immigrants by sex and by selected immigrant characteristics, compared with overall Canadian-born population (excluding Quebec)
Table summary
This table displays the results of Overall crude and age-standardized acute-care hospitalization rates(ASHRs Males, Females, Females, excluding pregnancy
and childbirth, Crude
rate, ASHR and 95% confidence interval (appearing as column headers).
Males Females Females, excluding pregnancy
and childbirth
Crude
rate
ASHR 95% confidence interval Crude
rate
ASHR 95% confidence interval Crude
rate
ASHR 95% confidence interval
from to from to from to
NHS Canadian-born population (weighted) 608 646 641 652 832 826 821 831 629 622 617 627
1980-to-2011 IMDB immigrants 332 358 356 361 596 545 543 547 325 331 329 333
Immigrant admission category
Economic 231 281 278 284 432 433 430 437 219 261 257 264
Principal applicants 301 283 273 294 508 523 504 541 285 280 265 294
Spouse and dependants 154 264 257 271 403 403 399 407 193 247 243 251
Family 478 409 405 414 778 620 616 624 442 361 357 365
Parents and grandparents 838 425 404 446 1,005 662 638 685 876 392 371 413
Spouse and dependants 311 393 385 400 680 579 573 585 263 321 315 327
Refugee 394 442 435 450 673 643 635 651 363 402 394 409
Resettled
Government assisted 524 480 437 524 728 792 741 843 485 456 417 494
Privately sponsored 514 470 377 564 635 798 636 960 447 452 330 573
Dependants of resettled refugees 229 411 378 445 661 621 609 632 328 381 370 392
Protected persons
In-Canada refugees 381 465 449 481 703 657 642 673 398 436 421 451
Dependants of protected persons 238 434 388 480 640 590 558 622 238 343 312 374
Others 576 442 398 485 774 611 585 638 579 388 364 412
Immigration landing year
1980 to 1989 558 400 396 405 670 554 549 559 545 369 364 373
1990 to 2002 352 359 355 362 529 487 484 491 341 327 324 330
2003 to 2011 206 279 275 283 645 538 534 542 209 268 264 271
Source world region
United States 354 421 406 436 577 624 608 639 374 417 402 431
Caribbean and Central and South America 375 426 416 435 720 666 657 674 435 433 426 441
Western Europe 418 423 415 431 645 626 617 635 432 415 406 423
Eastern Europe 400 429 420 438 606 556 549 564 354 355 348 362
Sub-Saharan Africa 352 443 429 458 802 719 706 732 362 419 407 431
Southwest Asia, Middle East and North Africa 313 370 363 378 622 572 564 580 302 352 345 359
South Asia 361 376 371 380 655 564 560 569 329 339 335 343
Southeast Asia 291 351 343 359 568 539 533 546 304 314 308 320
East Asia 220 223 219 227 405 375 372 379 216 208 205 212

The four leading disease-specific crude rates and ASHRs for male immigrants compared with Canadian-born males are shown in Table 4. Male refugees had the highest ASHRs for circulatory conditions and, to a lesser extent, digestive conditions. Similar to the overall hospitalization rates, the hospitalization rates for the top four conditions in male immigrants were lowest for recent arrivals and highest among more established immigrants, where ASHRs began to approach the rates for the Canadian-born population. Results by world region of birth show that Eastern European males had the highest rates for circulatory conditions (82.7; 95% CI=72.9 to 85.6) and cancers (43.3, 95% CI=41.4 to 45.2) among immigrants, while East Asian males had the lowest digestive disease, injury and circulatory disease rates.


Table 4
Leading disease-specific crude and age-standardized acute-care hospitalization ratesTable 4 Note  (ASHRs, per 10,000 population) among males by selected characteristics, for IMDB immigrants, compared with overall Canadian-born population (excluding Quebec)
Table summary
This table displays the results of Leading disease-specific crude and age-standardized acute-care hospitalization rates (ASHRs Circulatory disease (Rank #1), Digestive disease (Rank #2), Injury (Rank #3), Cancer (Rank #4), Crude
rate, ASHR and 95% confidence interval (appearing as column headers).
Circulatory disease (Rank #1) Digestive disease (Rank #2) Injury (Rank #3) Cancer (Rank #4)
Crude
rate
ASHR 95% confidence interval Crude
rate
ASHR 95% confidence interval Crude
rate
ASHR 95% confidence interval Crude
rate
ASHR 95% confidence interval
from to from to from to from to
NHS Canadian-born population (weighted) 94.7 103.8 102.3 105.2 78.4 82.1 80.9 83.4 59.3 61.5 60.6 62.4 45.3 49.1 48.2 50.1
1980-to-2011 IMDB immigrants 56.0 60.8 60.1 61.5 50.4 50.8 50.2 51.4 29.4 30.9 30.4 31.3 28.4 29.5 29.1 30.0
Immigrant admission category
Economic 38.2 48.0 46.9 49.0 39.2 42.7 41.8 43.6 21.3 24.5 23.9 25.1 23.1 28.6 27.8 29.4
Principal applicants 59.1 49.7 48.0 51.4 48.6 46.6 42.1 51.1 23.7 22.7 19.9 25.5 34.5 29.2 27.7 30.7
Spouse and dependants 15.2 42.6 40.1 45.0 28.7 41.2 39.2 43.3 18.6 25.0 23.5 26.5 10.6 27.0 25.1 29.0
Family 83.0 66.6 65.5 67.8 65.3 56.4 55.1 57.7 39.1 35.0 34.0 36.0 36.0 29.2 28.5 30.0
Parents and grandparents 165.3 70.3 68.6 72.1 96.2 58.3 53.0 63.6 55.0 34.1 29.5 38.8 62.4 28.3 27.1 29.4
Spouse and dependants 44.8 63.4 60.8 66.0 50.8 56.0 53.8 58.1 31.7 34.8 33.3 36.3 23.9 31.6 30.1 33.2
Refugee 65.2 75.8 73.3 78.3 60.0 61.4 59.4 63.4 37.7 41.1 39.7 42.6 31.7 34.5 33.0 36.1
Resettled
Government assisted 95.4 71.1 67.0 75.1 79.0 61.2 54.9 67.4 42.2 47.0 35.6 58.4 50.4 36.2 33.6 38.9
Privately sponsored 107.5 79.6 75.2 84.0 72.7 53.3 49.7 57.0 41.1 31.1 28.7 33.4 50.6 35.2 32.6 37.8
Dependants of resettled refugees 16.1 67.6 53.5 81.8 37.9 52.6 46.0 59.2 34.0 42.8 36.8 48.8 10.9 32.9 25.3 40.5
Protected persons
In-Canada refugees 61.9 83.3 77.7 89.0 58.8 63.3 58.9 67.7 36.8 41.5 38.6 44.5 25.5 31.7 28.6 34.8
Dependants of protected persons 22.8 75.6 59.8 91.5 40.8 73.8 56.8 90.9 29.0 34.7 28.5 40.8 11.2 30.9 21.6 40.2
Others 98.9 63.2 58.4 68.1 70.6 55.7 49.7 61.6 49.3 41.4 36.2 46.6 45.2 30.0 26.6 33.4
Immigration landing year
1980 to 1989 105.6 73.2 71.7 74.7 75.4 52.9 51.6 54.2 44.0 32.4 31.5 33.3 52.4 35.6 34.7 36.6
1990 to 2002 60.3 59.8 58.8 60.9 52.9 51.0 50.0 52.0 30.2 30.9 30.1 31.6 30.0 28.6 27.9 29.3
2003 to 2011 28.8 47.5 46.2 48.9 36.1 42.3 41.3 43.4 21.8 25.2 24.4 25.9 15.9 23.6 22.8 24.5
Source world region
United States 51.5 65.9 61.3 70.4 49.8 55.9 51.7 60.0 34.9 39.0 36.0 42.0 26.2 32.0 28.9 35.1
Caribbean and Central and South America 60.2 72.1 69.1 75.1 58.6 60.3 57.9 62.8 33.9 36.1 34.4 37.9 28.7 30.5 28.9 32.1
Western Europe 66.8 67.4 64.7 70.1 61.2 58.9 56.5 61.3 42.0 42.6 40.8 44.4 39.0 37.9 36.0 39.7
Eastern Europe 75.7 82.7 79.9 85.6 60.9 59.7 57.4 62.0 39.3 40.2 38.1 42.2 41.4 43.3 41.4 45.2
Sub-Saharan Africa 47.0 65.7 61.5 69.9 48.4 55.6 52.3 58.9 35.6 42.3 39.6 44.9 25.6 31.5 28.9 34.1
Southwest Asia, Middle East and North Africa 50.8 65.3 62.6 68.0 50.2 54.7 52.5 56.9 29.3 32.4 31.0 33.8 23.9 28.6 27.1 30.1
South Asia 69.8 72.1 70.5 73.6 52.1 50.9 49.6 52.3 28.0 29.0 28.1 29.8 22.6 22.7 21.8 23.6
Southeast Asia 50.3 61.5 58.9 64.0 51.0 55.3 53.0 57.6 21.7 24.8 23.4 26.1 28.5 32.6 30.8 34.4
East Asia 29.6 28.8 27.9 29.8 34.3 34.0 32.9 35.1 19.0 19.3 18.6 20.1 28.1 26.2 25.3 27.1

Table 5 shows the four leading disease-specific crude rates and ASHRs for female immigrants (excluding pregnancy) compared with Canadian-born females. Female refugees had the highest ASHRs for all four leading conditions. Similar to the overall hospitalization rates, the ASHRs for the four top conditions in female immigrants were lowest for those who landed in more recent years and increased with time spent in Canada, approaching the rates for the Canadian-born population. The ASHRs were consistently high for females from the Caribbean and Central and South America for all four leading conditions, while those for females from East Asia were consistently low.


Table 5
Leading disease-specific crude and age-standardized acute-care hospitalization ratesTable 5 Note  (ASHRs, per 10,000 population) among females, excluding pregnancy, by selected characteristics, for IMDB immigrants, compared with overall Canadian-born population (excluding Quebec)
Table summary
This table displays the results of Leading disease-specific crude and age-standardized acute-care hospitalization rates (ASHRs Cancer
(Rank #1), Digestive disease
(Rank #2) , Circulatory disease
(Rank #3), Genitourinary conditions
(Rank #4), Crude
rate, ASHR and 95% confidence interval (appearing as column headers).
Cancer
(Rank #1)
Digestive disease
(Rank #2)
Circulatory disease
(Rank #3)
Genitourinary conditions
(Rank #4)
Crude
rate
ASHR 95% confidence interval Crude
rate
ASHR 95% confidence interval Crude
rate
ASHR 95% confidence interval Crude
rate
ASHR 95% confidence interval
from to from to from to from to
NHS Canadian-born population (weighted) 51.3 50.6 49.8 51.3 79.0 78.3 77.1 79.6 66.0 64.9 63.8 66.1 53.6 53.1 52.3 53.9
1980-to-2011 IMDB immigrants 44.2 38.9 38.4 39.3 42.3 41.9 41.4 42.4 35.6 39.8 39.3 40.4 32.1 29.7 29.3 30.1
Immigrant admission category
Economic 38.8 38.0 37.2 38.8 31.8 35.3 34.4 36.2 15.9 25.3 24.3 26.2 23.5 23.6 23.0 24.3
Principal applicants 59.0 38.0 37.2 38.8 38.6 35.8 33.1 38.6 25.2 30.5 28.4 32.7 29.3 26.5 22.6 30.3
Spouse and dependants 31.1 39.5 38.9 40.2 29.2 33.9 32.9 35.0 12.4 22.2 21.1 23.3 21.2 23.3 22.5 24.0
Family 50.2 39.5 38.9 40.2 52.5 43.5 42.6 44.4 60.1 44.3 43.5 45.1 41.6 33.0 32.3 33.6
Parents and grandparents 71.6 45.5 41.3 49.7 90.9 41.1 38.3 44.0 160.3 50.3 49.1 51.5 66.1 39.0 32.2 45.8
Spouse and dependants 41.4 39.7 38.5 40.9 36.5 40.7 39.3 42.2 18.9 34.4 32.7 36.2 31.3 29.4 28.4 30.4
Refugee 45.4 41.9 40.5 43.4 50.4 52.3 50.4 54.1 34.6 47.1 44.9 49.2 36.6 35.4 33.9 36.8
Resettled
Government assisted 58.7 43.9 36.5 51.2 66.2 57.1 48.6 65.6 52.5 50.0 43.7 56.3 43.4 38.1 30.7 45.5
Privately sponsored 62.8 44.0 39.9 48.2 55.8 57.9 29.2 86.6 52.1 59.0 30.2 87.8 39.0 29.8 26.2 33.3
Dependants of resettled refugees 39.3 40.0 37.8 42.3 47.4 51.0 48.2 53.8 28.6 43.8 40.5 47.1 34.2 34.0 31.9 36.1
Protected persons
In-Canada refugees 50.7 46.1 43.2 49.0 55.0 55.9 52.2 59.5 39.7 51.2 47.1 55.3 40.5 38.7 35.9 41.4
Dependants of protected persons 30.3 38.6 31.7 45.6 32.3 36.8 30.1 43.4 15.9 39.7 28.0 51.4 28.5 33.4 27.1 39.7
Others 63.4 45.5 41.3 49.7 67.4 50.3 44.9 55.7 80.2 39.0 35.7 42.3 44.1 32.1 28.4 35.8
Immigration landing year
1980 to 1989 65.1 42.0 41.0 43.0 63.7 43.9 42.8 45.1 72.9 47.9 46.7 49.0 47.5 32.9 31.9 33.8
1990 to 2002 48.7 39.4 38.7 40.0 43.0 41.0 40.2 41.8 38.5 39.2 38.4 40.0 33.9 29.5 28.9 30.1
2003 to 2011 29.7 34.7 33.9 35.6 32.2 36.6 35.7 37.5 16.0 28.8 27.7 29.8 23.3 25.8 25.1 26.5
Source world region
United States 38.7 39.8 37.0 42.7 51.8 55.1 51.5 58.7 29.9 39.1 35.1 43.2 37.3 37.8 34.7 40.9
Caribbean and Central and South America 60.1 49.1 47.7 50.6 60.2 59.3 57.1 61.4 47.9 52.1 50.1 54.2 47.4 42.4 40.9 43.9
Western Europe 48.0 40.4 38.6 42.1 55.9 53.3 51.0 55.5 43.9 44.9 42.7 47.2 42.6 37.3 35.7 38.9
Eastern Europe 51.6 44.2 42.7 45.8 45.8 45.9 44.1 47.7 44.4 49.0 47.1 50.9 32.9 30.3 29.0 31.7
Sub-Saharan Africa 47.7 45.3 43.0 47.6 46.0 51.8 48.8 54.8 28.4 41.6 38.5 44.7 33.2 33.5 31.5 35.6
Southwest Asia, Middle East and North Africa 36.6 37.5 35.9 39.0 41.0 43.7 41.9 45.5 31.1 45.5 43.0 47.9 29.2 30.3 28.9 31.7
South Asia 35.9 32.7 31.9 33.6 38.6 38.6 37.5 39.6 41.4 45.6 44.3 46.9 33.7 31.8 30.9 32.7
Southeast Asia 52.1 44.6 43.2 46.0 43.7 43.3 41.7 45.0 33.2 38.7 36.9 40.4 34.0 31.0 29.8 32.2
East Asia 39.2 32.6 31.8 33.4 28.4 27.4 26.5 28.2 20.8 21.2 20.4 22.0 17.9 16.2 15.6 16.8

Discussion

This study found lower rates of hospitalization among male and female immigrants, compared with Canadian-born individuals. Among immigrants, the lowest rates of hospitalization were seen among those who had arrived in Canada more recently, who were part of the economic class and whose country of origin was in East Asia. The health of immigrants is influenced by a number of factors, such as the conditions in their original home country, why and when they migrated, and their experiences after arrival in Canada.Note 26 The results of this study concerning hospitalization rates among groups of immigrants, compared with their Canadian-born counterparts, can inform health screening policy and strategic health care planning for immigrants to Canada.

Similar to previous work,Note 3Note 4Note 5Note 6Note 7Note 8Note 9 results from this study support the existence of a HIE, as immigrants have almost half the overall ASHR compared with Canadian-born males and females, excluding hospitalizations related to pregnancy and childbirth. In addition, similar to a previous study using the IMDBDAD linkage,Note 11 non-pregnancy-related ASHRs were lowest among the most recently arrived immigrants, providing support to previous studiesNote 5Note 11 that suggest that the magnitude of the HIE may decrease over time. The top four causes of non-pregnancy-related hospitalization were circulatory disease, digestive disease, injury and cancer among males, and cancer, digestive disease, circulatory disease and genitourinary conditions among females. These causes of hospitalization were similar to those found in the previous IMDBDAD study,Note 11 with the exception that among females in this study, genitourinary conditions (ICD-10-CA Chapter 14) replaced injury as the fourth leading cause of hospitalization, while injury ranked fifth in the current study.

Economic-class immigrants, composed of skilled workers and other professionals, had the lowest ASHRs, followed by family-class immigrants and refugees. There are several selection factors that may be associated with better health status among economic immigrants. Economic immigrants must demonstrate their capacity to integrate into the Canadian economy as part of the selection process,Note 2 requirements that would exclude individuals who are not healthy enough to work. By contrast, family-class immigrants are selected based on their relationship with current Canadian citizens or permanent residents, and refugees are selected based on their need for protection.Note 2 As such, family-class immigrants and refugees may include individuals with health conditions that could impact their ability to work, potentially making economic immigrants systematically less likely to require hospitalization than other classes of immigrants. The finding of higher ASHRs among refugees is consistent with previous analyses of immigration dataNote 11Note 27 and may be partially attributable to pre-migration experiences, including poor sanitation and nutrition, reduced health care access, and mental health concernsNote 28 that could be associated with increased risk of hospitalization after their arrival in Canada.

In addition, there are also differences in health screening practices for economic applicants that may partially explain their lower ASHRs, compared with family- and refugee-class immigrants. Specifically, under the 2002 Immigration and Refugee Protection Act, refugee- and family-class immigrants (with the exception of parents and grandparents) are exempt from medical inadmissibility based on excessive demand for Canada’s publicly funded health or social services.Note 2 By contrast, the excessive demand provision continues to apply to economic applicants. Thus, some family- and refugee-class immigrants could have been deemed inadmissible on health-related grounds had they applied to the economic stream and been diagnosed with a health condition more likely to require hospitalization. This hypothesis is consistent with a previous study, where immigrants to Canada were less likely than immigrants to the United States to report having a serious chronic health condition, as the United States does not consider excessive demand in its health screening process.Note 29

When world region of origin is considered, ASHRs were lowest among immigrants from East Asia (males and females) and highest among male immigrants from Sub-Saharan Africa and female immigrants from the Caribbean and Central and South America. These results are consistent with a previous study of cardiovascular disease hospitalization rates in Ontario, where the rates for Chinese immigrants were substantially lower than those for South Asian and European immigrants, as well as for non-immigrants.Note 30 A combination of sociodemographic factors,Note 31Note 32 lifestyle characteristicsNote 33 and use of traditional medicines,Note 34 as well as differential health system use (e.g., less contact with general practitioners) and accessNote 35Note 36 by East Asian immigrants, could contribute to these results. In addition, ongoing epidemiologic transitions with an increasing proportion of morbidity and mortality attributable to chronic diseases in both Sub-Saharan AfricaNote 37 and the Caribbean and Central and South AmericaNote 38 could also contribute to the elevated hospitalization rates among immigrants from these regions. By contrast, risk factors associated with chronic disease, such as tobacco use and overweight and obesity, contribute to a smaller burden of disease in some East Asian countries.Note 39 However, differences in the mix of immigrant types from different world regions may also partially explain the observed differences in ASHRs. For example, 68% of immigrants from East Asia in the IMDBDAD database were economic-class applicants, compared with 36% of applicants from Sub-Saharan Africa and 33% from the Caribbean and Central and South America. As previously described, there are differences in health screening requirements across application classes that may influence the subsequent risk of hospitalization.

A number of methodological issues have been accounted for in this study. To refine the calculation of hospitalization rates, tax file records that are part of the IMDB were used to remove approximately 17% of immigrants who landed in Canada as permanent residents since 1980, who were presumed to have emigrated by 2011. While the measurement of emigration is complex and the use of tax records may underestimate it to some degree, their good population coverage and the fact that they are an annual direct measure with timely availability are advantages of this strategy.Note 40 To improve completeness, mental health hospitalization discharge data from Ontario were included in this study by linking the discharge-related records from the OMHRS in the SDLE. Interestingly, mental health was ranked as the fifth leading cause of hospitalization in male immigrants and the sixth leading cause among females (excluding pregnancy). Further investigation is warranted to better understand the mental health needs of immigrants and will be the subject of a subsequent analysis. Finally, this study is further strengthened by the removal of hospital transfers in the DAD and the OMHRS. By converting these transfers to single hospitalization events and calculating ASHRs, it was possible to refine the comparison of immigrant hospitalization rates with those of the Canadian-born population.

Limitations

A number of potential confounding factors may have influenced the observed differences in ASHRs between subgroups of the immigrant cohort. For example, the distribution of applicants in various admission classes differs by country of origin, and this could partially confound differences in ASHRs between immigrants by world region. Differences in the countries of origin among cohorts of immigrants arriving in the 1980s, compared with the 2000s, could also have influenced the observed differences in ASHRs by immigrant landing year. Further, while all hospitalization rates were age-standardized based on age on Census Day 2011, the current analysis did not account for age at migration. If migration at a younger age influences the risk of subsequent hospitalization and is also related to any of the measured immigration characteristics (e.g., immigration class), the observed differences between subgroups of immigrants could be confounded. Future studies employing a multivariate analytical approach that can account for potential confounders may allow for further refinement and identification of driving factors associated with differences in ASHRs between subgroups of immigrants, while adjusting for additional characteristics, like age at migration.

As previously described,Note 11 hospital use is somewhat limited as a proxy for health status since it does not capture other aspects of health system use (e.g., primary care) that may relate to conditions not requiring hospitalization. Hospital discharge data typically represent more severe outcomes along the spectrum of disease, and, therefore, it would be useful to interpret the findings of this study within the context of other immigration health indicator data. However, given that these limitations apply to both the immigrant and the Canadian-born cohorts, this study offers a unique comparison of hospitalization between these populations to support the evidence base on health care utilization patterns in Canada as well as migration health trends, such as the HIE.

Conclusion

This study generates new knowledge on hospitalization events among immigrant and Canadian-born populations using linked administrative immigration and hospital data. The results show that immigrants have lower acute-care hospitalization rates than the Canadian-born population, even after age standardization. These results improve upon previous workNote 11 by including a Canadian-born reference cohort and support the results of previous studies that have demonstrated the existence of the HIE in Canada, the magnitude of which tends to decrease over time.Note 3Note 4Note 5Note 6Note 7Note 8Note 9 This study demonstrated that the lowest ASHRs are seen among economic immigrants, an observation that applies to both males and females across the four leading causes of hospitalization.

Data from the 2016 Census indicate that one in five Canadians are immigrants;Note 1 therefore, knowledge on immigrant health is critical to inform health system policy and planning. Future areas of study that could further contribute to understanding patterns of immigrant health include more detailed analyses of specific causes of hospitalization (e.g., mental health), as well as multivariate analyses to account for differences across immigrant subgroups. Increased understanding of both the patterns and the determinants of immigrant health outcomes is essential to informing future health policy making, including immigrant health screening, health promotion and interventions aimed at improving continuity of care over the course of settlement in Canada.

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