Acute care hospital days and mental diagnoses

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Despite an increase in population-based studies of mental health at the national and provincial levels,^1-6 substantial gaps remain in understanding the impact of mental illness on the use of health care services. Reports tend to focus on mental conditions as a most responsible diagnosis and provide limited information about mental illness as a co-morbidity. However, psychiatric disorders can accompany physical conditions, and many physical conditions increase the risk of poor mental health.^7-10 The combination of physical and mental conditions may result in higher rates of health care use, because mental illness often complicates help-seeking, diagnosis and treatment, and may influence prognosis.^11-14

Based on administrative data for acute care hospitals, this study examines hospitalizations with a most responsible or comorbid mental diagnosis (see The data). Rather than the number of hospitalizations, the analysis is based on the number of days and the average length of stay. The total number of days provides a proxy measure of resource use in the acute care hospital system, and the average length of stay is an indication of the intensity of hospital service use. This study updates an earlier working paper,¹⁵ but unlike that report, does not include Quebec because of data limitations.

Less than 1% of population use a quarter of hospital days

In 2009/2010, approximately 182,000 people with a mental diagnosis were separated at least once from an acute care hospital (data not shown). They made up 0.7% of the population, but 11.8% of all patients separated from hospital that year. For one-third of these patients (61,900), a mental condition was the most responsible diagnosis, and for the remaining two-thirds (120,500), a mental condition was listed as a comorbidity. These patients accounted for 25.5% of all hospital days: 9.0% (about 1.3 million days) were attributable to a most responsible mental diagnosis, and 16.5% (2.3 million days) involved a comorbid mental diagnosis (Table 1).

Among male and female patients, similar percentages of acute care hospital days were attributable to mental diagnoses. A most responsible mental diagnosis was recorded for 9.2% and 8.9% of the days used by male and female patients, respectively (data not shown). The corresponding figures for comorbid mental diagnoses were 17.3% and 15.9%.

Table 1 Acute care hospital days, by age group and presence of mental diagnosis, Canada excluding Quebec, 2009/2010

Patterns vary by age

The percentage of acute care hospital days involving mental diagnoses varied by the patients' age and by whether the mental condition was the most responsible or a comorbid diagnosis.

The percentage of hospital days attributable to a most responsible mental diagnosis was highest among patients aged 10 to 19 (Table 1).; Almost 30% of all days that 10- to 19-year-olds spent in hospital in 2009/2010 had a most responsible mental diagnosis. Among patients at progressively older ages, the percentage of days with a most responsible mental diagnosis generally declined, and by age 50 or older, was less than 10%.

By contrast, the percentage of hospital days with a comorbid mental diagnosis rose with age from fewer than 10% of days among patients younger than age 40 to about a quarter of days among those aged 80 or older.

Longer stays

Mental diagnoses, whether most responsible or comorbid, were associated with much longer hospital stays—overall, more than two and a half times as long―than stays not involving a mental diagnosis (Table 1). This pattern held among patients of all ages.  For example, patients in their twenties who did not have a mental diagnosis averaged 2.7 days in hospital; their contemporaries with a most responsible mental diagnosis averaged 11.9 days, and those with a comorbid mental diagnosis, 6.1 days. For patients in their seventies, the averages were 7.8 days for stays without a mental diagnosis, 27.0 days for stays with a most responsible mental diagnosis, and 19.5 days for stays with a comorbid mental diagnosis.

Mental disorders

The three mental diagnoses accounting for the largest number of most responsibleacute care hospital days were organic disorders (dementia, delirium) (461,000), mood disorders (313,000), and schizophrenic/psychotic disorders (266,000) (data not shown). The three comorbidmental diagnoses accounting for the largest numbers of days were organic disorders (1,404,000), mood disorders (600,000) and substance-related disorders (537,000).

As expected, the number of most responsible and comorbid days attributable to organic mental disorders were greatest for patients aged 70 or older (data not shown). Days attributable to substance-related disorders were prevalent over a wide range of ages, usually as a comorbidity. Days attributable to mood disorders appeared primarily as a most responsible diagnosis at young ages, but shifted to a comorbid diagnosis at older ages. Schizophrenic/Psychotic conditions were prevalent as a most responsible diagnosis from ages 20 to 60.

Diseases associated with mental comorbidity

The percentage of acute care hospital days involving mental comorbidity differed by major disease type (Table 2). The figure ranged from 2.4% of days for hospitalizations related to pregnancy to 24.8% of days for hospitalizations for diseases of the nervous system (for instance, Parkinson's Disease). Other disease types with a relatively high percentage of days with a comorbid mental diagnosis were metabolic (22.9%), injury/poisoning (23.6%), and infectious/parasitic (23.1%).

Table 2 Acute care hospital days, by major disease type and presence of mental diagnosis, Canada excluding Quebec, 2009/2010

Regardless of disease type, a mental comorbidity was associated with a substantial increase in the average length of stay. For instance, patients with a most responsible diagnosis of neoplasm (cancer), but no mental comorbidity, averaged 7.6 days in hospital; for those with a mental comorbidity, the average length of stay was 21.0 days. Among patients hospitalized because of a circulatory disease, the corresponding averages were 7.1 days and 17.2 days.

Alternate level of care

The term alternate level of care(ALC) identifies hospital patients who have completed the acute care phase of their treatment, but who still occupy a bed because of ongoing post-acute care needs or the unavailability of supports in the community.^20,21 These patients may stay in acute care hospitals for a long period. Previous analyses indicate that dementia is the most common diagnosis for longer stay ALC patients,²² and that a psychiatric diagnosis is common in ALC patients.²³

In fiscal year 2009/2010, ALC patients accounted for 13% of hospital days (more than 1.8 million). About one-quarter of hospital days attributable to mental diagnoses were designated ALC versus 9% of days not associated with a mental diagnosis (Table 3).

Table 3 Percentage of acute care hospital days designated alternate level of care, by age group and presence of mental diagnosis, Canada excluding Quebec, 2009/2010

This study has several limitations. The results refer to acute care hospitalizations; because psychiatric hospitals were not included, hospitalizations for some of the most severe mental conditions are missing from the analysis. In fact, psychiatric hospitals account for around 15% of all mental-related hospitalizations.¹ As well, emergency departments were not covered in this study. Finally, the validity of conclusions drawn from analyses of large administrative databases depends on the accuracy of case-defining diagnostic codes, which could not be determined.

Conclusion

In 2009/2010, people hospitalized with a mental diagnosis represented less than 1% of the population, but they used 25% of acute care hospital days. Two-thirds of these days involved a mental comorbidity. The average length of stay for patients with a comorbid mental diagnosis was more than two and a half times the average for patients who did not have a mental diagnosis, regardless of the patients' age and primary diagnosis. In addition, about one quarter of all mental health days were designated as ALC, indicating possible ongoing care needs or unavailability of support in the community.