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Multiple sclerosis: Prevalence and impact

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by Heather Gilmour, Pamela L. Ramage-Morin and Suzy L. Wong

Estimates from individual provinces suggest that the prevalence of multiple sclerosis (MS) among Canadians may be one of the highest in the world.^{Note 1Note 2Note 3} MS is a progressive, potentially disabling disease of the central nervous system that damages myelin, the protective layer surrounding nerves. This disrupts communication to and from the brain, producing symptoms such as vision impairment, loss of coordination and balance, extreme fatigue, pain, bladder dysfunction, cognitive impairment, numbness, weakness, and mood changes.^{Note 4Note 5} The nature and severity of symptoms vary and may be characterized by periods of relapse and remission.

While the cause of MS is unknown, differences by region, sex, and ethnicity have led researchers to investigate sex hormones, diet, genetic factors, and environmental conditions, such as exposure to ultraviolet radiation.^{Note 6Note 7Note 8Note 9} Results have been inconclusive and are complicated by different data sources—from self-reports to clinical assessment—and by factors including changes in population composition through natural increase and migration.^{Note 2Note 8}

This study examines the prevalence of MS and its impact on those diagnosed.^{Note 6} MS among Canadians in private households is based on self-reported data from two nationally representative surveys: the 2010/2011 Neurological Conditions Prevalence File and the 2011 Survey on Living with Neurological Conditions in Canada. In-depth information from the latter is presented for household residents aged 15 or older, including age at diagnosis, comorbidity, treatment, and impact. Based on the 2011/2012 Survey of Neurological Conditions in Institutions in Canada, for the first time, the prevalence of MS among people in long-term care facilities is reported. Deaths due to MS are from the Canadian Vital Statistics, Death Database (see The data).

Prevalence

In 2010/2011, based on the most recent nationally representative data, an estimated 93,500 Canadians reported a diagnosis of MS. At 290 cases per 100,000 population (Table 1), prevalence exceeded that in many other countries and was higher than reported in earlier Canadian studies.^{Note 2Note 10} Global estimates vary widely, and differing methodologies make direct comparisons between studies difficult. The United Kingdom, for example, reports a rate per 100,000 of 203; Sweden, 189; and Ecuador, 3.2.^{Note 6Note 11Note 12} Increased prevalence in recent years is thought to be attributable to longer survival time and advances in diagnosis rather than to changes in disease risk.^{Note 13Note 14}

Women are two to three times more likely than men to have MS. The imbalance in the sex ratio is thought to be increasing in several countries, including Canada,^{Note 13} where 2.6 women reported MS for every man with the condition. This disparity is reflected in prevalence estimates of 418 cases per 100,000 women and 159 cases per 100,000 men.

MS is much more common among people in long-term care facilities. In 2011/2012, an estimated 3,800 long-term care residents were reported to have MS, which equates to 1,460 cases per 100,000 (95% CI: 1,380 to 1,540). As in the household population, women were significantly more likely than men to have MS. Prevalence peaked in the 45-to-64 age range.

Age at diagnosis

In Canada and other countries,^{Note 11Note 15} MS is usually diagnosed before age 50—82% of household residents aged 15 or older reporting MS had been diagnosed at ages 20 to 49 (95% CI: 75.9 to 86.5). The average age at which people first experienced symptoms was 32, with a diagnosis about five years later at age 37.

Consistent with previous work,^{Note 16Note 17} the time between the onset of symptoms and diagnosis was longer for women than for men and for those whose symptoms appeared at earlier ages (Table 2). The gap between the appearance of symptoms and diagnosis was 5.4 years for women, compared with 2.6 years for men (p < 0.01). The gap was longer for people whose symptoms began before age 20, and shorter for those whose symptoms appeared at age 40 or later, compared with those whose symptoms appeared at ages 30 to 39. People with MS had lived with the condition for an average of 15 years, although for some, the period extended beyond 50 years.

Non-neurological comorbidity

Research has shown that comorbidities in MS affect disability progression, quality of life, need for health care, and mortality risk.^{Note 18Note 19Note 20} In this study, people aged 15 or older with MS were about 15 times more likely than the general population to report urinary or bowel incontinence (59% versus 4%), which may be due, in part, to damage to the nerve pathways from the brain to the bladder and the bowels^{Note 21Note 22} (Figure 1). They were more than three times as likely to have a mood disorder (22% versus 7%). A combination of biological, behavioural, psychological, and disease-related factors are thought to contribute to this pattern.^{Note 23} On the other hand, the prevalence of diabetes, heart disease, and high blood pressure among people with MS did not differ significantly from the general population, and other research has found a reduced risk of cancer among MS patients.^{Note 24}

Impact

For survey respondents with MS and other neurological conditions, it is not possible to separate impacts that may be due to MS from those due to the other disorders. Consequently, analysis of the impact of MS was restricted to individuals whose only neurological condition was MS (68%; 95% CI: 62 to 74). This may introduce a bias if those with multiple neurological conditions experience greater impacts overall.

About two-thirds of these people reported that MS affected their lives moderately, quite a bit, or extremely (Table 3). The remaining third stated that their lives were affected only a little bit or not at all.

It is difficult to generalize about the impact of MS because it can manifest in many ways and affect different parts of the body to varying degrees. Although 57% of people with MS could walk without aid, almost a third (31%) required a wheelchair, a mechanical aid such as a cane or walker, or the help of another person; 12% could not walk at all. Just over half (53%) were usually pain-free, with the rest reporting pain that prevented a few activities (21%) or some/most activities (25%). Nearly two-thirds (62%) experienced difficulty getting a good night's sleep.

In addition to physical effects, MS may have cognitive impacts at any stage. Half (50%) of people whose only neurological condition was MS had difficulty remembering most things and/or thinking and solving problems.

MS was limiting in other ways. About a third reported that it had prevented them from driving (30%), or compromised their educational opportunities (32%). More than half (58%) experienced at least some limitations in job opportunities; 44% characterized these limitations as “quite a bit” or “extreme.” As well, 43% reported that MS had a negative impact on their social interactions; for instance, they felt left out, embarrassed, or perceived that others felt uncomfortable around them or avoided them.

Treatment

There is no cure for MS, although treatments are available to help manage the disorder,^{Note 14} including pharmaceuticals, physiotherapy, occupational therapy, cognitive rehabilitation, and complementary and alternative therapies.^{Note 7} The use of “liberation therapy,” a controversial treatment that dilates narrowed neck veins,^{Note 25} is unsupported for the management of MS patients, based on recent results from a large clinical trial in Canada.^{Note 26}

A majority (83%) of Canadians aged 15 or older with MS reported using one or more treatments (Table 4). Of those, 84% took medications, and 49% had rehabilitation therapy. Counselling and complementary medicine were used by 27% and 25%, respectively. Smaller percentages reported urinary catheterization and liberation therapy. Of those who received treatment, 39% reported one type, and the remaining 61% had multiple treatment strategies.

Deaths

Life expectancy is shorter for people with MS,^{Note 20Note 27} the most common cause of death being MS itself or related complications such as infections. In 2013, of the total 252,338 deaths that occurred in Canada, MS was the underlying cause for 521 (1.5 per 100,000 population). It was a less common cause of death than Parkinson’s disease (2,354 deaths; 6.7 per 100,000) and Alzheimer’s disease (6,345 deaths; 17.9 per 100,000), but more common than epilepsy (240 deaths; 0.7 per 100,000) and cerebral palsy (160 deaths; 0.5 per 100,000).

Conclusion

This study presents up-to-date national estimates of the prevalence of MS and highlights many condition-specific impacts on the lives of those with MS. The prevalence of MS in Canada is among the highest reported in the world. An estimated 93,500 Canadians in private households, and 3,800 in long-term care facilities, have MS. It is most frequently diagnosed between the ages of 20 and 49.

Unlike neurological disorders such as dementia^{Note 28} and Parkinson’s disease^{Note 29} that tend to develop at older ages, MS is more prevalent in younger adults. Longer duration and the potential early loss of productivity due to physical disability, fatigue, comorbidity, and need for assistance affect the societal cost of MS.^{Note 12}

Acknowledgments

Statistics Canada thanks all participants for their input and advice during the development of neurological content for the Canadian Community Health Survey, the Survey on Living with Neurological Conditions in Canada, and the Survey of Neurological Conditions in Institutions in Canada. The content of these surveys was developed jointly by the Health Statistics Division at Statistics Canada and the Public Health Agency of Canada (PHAC), with input from PHAC’s expert advisory group members who specialize in the study of neurological conditions. Content was selected based on objectives and data requirements specified by PHAC. Sponsorship was provided by PHAC as part of the National Population Health Study of Neurological Conditions. Special thanks to Gisèle Carriere for her review and insightful comments.

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