Prevalence of Individuals Experiencing the Effects of Stroke in Canada
Trends and Projections
Background and Purpose—Previous estimates of the number and prevalence of individuals experiencing the effects of stroke in Canada are out of date and exclude critical population groups. It is essential to have complete data that report on stroke disability for monitoring and planning purposes. The objective was to provide an updated estimate of the number of individuals experiencing the effects of stroke in Canada (and its regions), trending since 2000 and forecasted prevalence to 2038.
Methods—The prevalence, trends, and projected number of individuals experiencing the effects of stroke were estimated using region-specific survey data and adjusted to account for children aged <12 years and individuals living in homes for the aged.
Results—In 2013, we estimate that there were 405 000 individuals experiencing the effects of stroke in Canada, yielding a prevalence of 1.15%. This value is expected to increase to between 654 000 and 726 000 by 2038. Trends in stroke data between 2000 and 2012 suggest a nonsignificant decrease in stroke prevalence, but a substantial and rising increase in the number of individuals experiencing the effects of stroke. Stroke prevalence varied considerably between regions.
Conclusions—Previous estimates of stroke prevalence have underestimated the true number of individuals experiencing the effects of stroke in Canada. Furthermore, the projected increases that will result from population growth and demographic changes highlight the importance of maintaining up-to-date estimates.
The effects of a stroke can range from mild to severe, and among those who survive their stroke, many never fully recover. Approximately 36% of these survivors are left with significant disabilities 5 years after their stroke1 and >40% require assistance with activities of daily living.2 Complete and inclusive data that report on stroke survivorship and stroke disability among populations are essential for agencies charged with planning for the provision of services to those who have experienced a stroke, as well as for monitoring improvements in treatment and prevention.
In Canada, available information on stroke survivorship is limited, and when it is reported, it is typically an imprecise approximation. Hodgson3 estimated that there were 261 000 stroke survivors living in Canada in 1995, a value that has become outdated because of changing stroke incidence, improved treatments, and an aging population. More recently, various governmental and nongovernmental agencies have quoted that approximately 315 000 Canadians are living with the effects of stroke.4,5 This estimate, however, is based solely on results from the Canadian Community Health Survey (CCHS), which is self-reported and fails to account for critical subgroups in the population, including children aged <12 years and those living in institutions.
Several other jurisdictions have approximated the prevalence of stroke survivorship and stroke disability among their populations; however, these estimates are difficult to relate to other regions because of different population characteristics, risk factors, and treatment practices.
The purpose of this study is to provide an updated estimate of the prevalence of individuals experiencing the effects of stroke in Canada (and its regions) based on the analysis of data from multiple sources. In addition to deriving an estimate of the number of individuals experiencing the effects of stroke in 2013, we calculate trends in Canada since 2000 and a forecast through to 2038. The majority of stroke survivors are adults living in the community; therefore, we calculated the prevalence, trends, and projected number of individuals experiencing the effects of stroke using Canada-specific data and adjusted it to account for children aged <12 years and individuals living in homes for the aged. Collectively, these 3 populations capture almost all stroke survivors in Canada.
Materials and Methods
Estimates of prevalence, trends, and projected number of individuals experiencing the effects of stroke were produced for Canada as a whole, as well as using region-specific data for the following regions: the Atlantic provinces (Prince Edward Island, Newfoundland and Labrador, New Brunswick, and Nova Scotia), Quebec, Ontario, the Prairie provinces (Manitoba, Saskatchewan, and Alberta), and British Columbia. The Northwest Territories, Yukon, and Nunavut were excluded from our regional analysis, but included in our analysis of Canada as a whole.
We define individuals experiencing the effects of stroke as individuals who have been diagnosed by a health professional as having had a stroke with resulting cognitive or physical effects that have lasted, or are expected to last, at least 6 months. Many individuals who have had a transient ischemic attack or stroke have no such cognitive or physical consequences and are thus excluded from our analysis.
Stroke Prevalence in the Community-Dwelling Population
The CCHS survey has been conducted annually since 2007 (with data combined into 2-year cycles), and biennially before that. The CCHS produces a Public Use Microdata File that includes annual and combined data for 2-year periods.6 We estimated the number of individuals experiencing the effects of stroke using data from the 2000/2001, 2003, 2005, 2007/2008, 2009/2010, and 2011/2012 CCHS cycles. Each cycle included ≈130 000 survey respondents. Age-, sex-, and region-specific prevalence values were calculated from the weighted number of responses to the question: Do you suffer from the effects of a stroke? (microdata file variable CCC_151).6* This question was prefaced with the statement: Remember, we’re interested in conditions diagnosed by a health professional and that are expected to last or have already lasted 6 months or more. Ages were grouped as follows: 12 to 39, 40 to 44, 45 to 49…75 to 79, ≥80 years. The CCHS does not survey individuals living in institutions, on Aboriginal reserves, or in the Canadian Forces; therefore, we assume that all these populations, excluding individuals living in homes for the aged, have the same rates of stroke as the surveyed portion of the Canadian population. The number of community-dwelling individuals experiencing the effects of stroke aged ≥12 was calculated using age-, sex-, and region-specific prevalence values based on CCHS data multiplied by population estimates7 (minus the number of residents of homes for the aged, calculated as below).
Stroke Prevalence in Homes for the Aged
The number of individuals living in homes for the aged in 2013 was estimated based on trends from 2000/2001 to 2009/2010 for each region8 as well as population growth.7 Data were not available by age or sex for Quebec; therefore, we distributed the Quebec population living in homes for the aged to age and sex groups based on the Canadian average. Canadian data from 2012/2013 suggest that 21.9% of residents in homes for the aged have been diagnosed with a stroke.9 This is within the range of estimates from other countries (18%–25%)10,11 (see online-only Data Supplement).
Stroke Prevalence in Children
We calculated the incidence of ischemic and hemorrhagic stroke in children aged <1 year (7.90 and 1.53/100 000, respectively) and 1 to 11 (0.74 and 0.55/100 000, respectively) based on 5 years of Canadian hospitalization data.12 We assumed a mortality rate of 9% after ischemic stroke and 25% after hemorrhagic stroke, and that 62% of ischemic and 32% of hemorrhagic strokes result in disability, based on combined data from multiple studies.13 Finally, the male to female predominance in pediatric stroke is ≈1.5:1.14,15 From these values we estimated that the prevalence of stroke among males and females aged 0 to 11 years was 10.3 and 7.3/100 000, respectively (see online-only Data Supplement).
Overall population prevalence rates for each region were calculated as the sum of individuals experiencing the effects of stroke in the above 3 groups, with the population for the region of interest as the denominator. All calculated prevalence rates were age adjusted to the 2013 Canadian population.
Projected Stroke Prevalence in 2038
We forecasted the prevalence of individuals experiencing the effects of stroke between 2013 and 2038 using 4 different approaches (referred to as projections A–D). All age-, region- and sex-specific population projections were based on the Statistics Canada medium growth–historical trends (1981–2008) scenario (M1).16 For projection A, we assumed that the age-, region-, and sex-specific prevalence of individuals experiencing the effects of stroke would remain the same for all years as in 2011/2012; in projection B, we assumed that the prevalence would remain the same as the weighted average for 2007/2008, 2009/2010, and 2011/2012; and in projection C, we assumed that the prevalence would remain the same as the weighted average for all 6 CCHS cycles. To calculate projection D, we performed a linear regression analysis on all age-, region-, and sex-specific prevalence rates from 2000/2001 to 2011/2012. If trends were both significant (P<0.05) and had a predicted R2 > 50%, they were used to forecast future prevalence rates. For populations in which the regression analysis did not meet these 2 criteria, the weighted average of all CCHS cycles was used to project stroke prevalence (as in projection C; see online-only Data Supplement).
To estimate the prevalence among residents of homes of the aged, all projections used forecasted rates of residential home occupancy based off of 10 years of age- and sex-specific trends from Statistics Canada.8 As above, we assumed that 21.9% of residents of homes for the aged were experiencing the effects of stroke. We assumed the prevalence of children experiencing the effects of stroke remained consistent across years. We applied these prevalence rates to population estimates7 for years 2013 and 2014 and population projections16 for years 2015 to 2038.
We tested the assumption that there would be a 1% annual relative increase in age- and sex-specific prevalence rates starting in 2013, as well as a similar 1% decrease.
Stroke Prevalence in 2013
An estimated 405 000 Canadians were experiencing the effects of stroke in 2013, yielding an overall population prevalence of 1.15% (Table 1). Among males, the overall prevalence was 1.10% (191 000 individuals) and among females was 1.21% (214 000 individuals). Of the 405 000, an estimated 354 500 (87.6%) are community-dwelling adults, 49 900 (12.3%) live in homes for the aged, and 400 (0.1%) are children. As expected, the prevalence of stroke increases substantially with age (Figure 1). The age-adjusted prevalence of individuals experiencing the effects of stroke varies across the country from a low of 1.04% in Quebec to a high of 1.26% in Ontario (Table 2).
Trends in Stroke Prevalence
For Canada as a whole, the age-adjusted prevalence of individuals experiencing the effects of stroke ranged from a maximum of 1.23% in 2005 to a minimum of 1.14% in 2009/2010 (Figure 2). Although all regions demonstrated an overall decreasing trend in age-adjusted prevalence, none of these trends were statistically significant. Despite relatively stable prevalence rates between 2000 and 2013, the total number of individuals experiencing the effects of stroke in Canada increased by 95 000 (31%) as a result of population growth and aging (Table 3).
Projected Stroke Prevalence in 2038
The number of individuals experiencing the effects of stroke in Canada is projected to increase from 405 000 in 2013 to between 654 000 and 726 000 in 2038 (Figure 3). This represents an expected increase from 2013 that ranges between 62% and 79%. In some regions, we expect that the prevalence of individuals experiencing the effects of stroke will as much as double by 2038. The overall prevalence in the population is expected to increase from 1.15% in 2013 (Table 1) to between 1.50% and 1.67% in 2038 (data not shown). The largest increase is projected for the Prairie provinces, where we estimate that there will be between 116 000 and 132 000 individuals experiencing the effects of stroke in 2038. This represents an expected increase from 2013 that ranges between 100% and 128%.
A sensitivity analysis testing the assumption that the prevalence of stroke increases by a relative 1% annually suggests that 923 000 individuals would be experiencing the effects of stroke in 2038, whereas a similar 1% decrease would result in 560 000.
We estimate that there were ≈405 000 individuals experiencing the effects of stroke in Canada in 2013, a value that is considerably higher than commonly quoted estimates of 315 000. Primarily, this difference is because of the failure of previous estimates to account for children aged <12 years and individuals living in homes for the aged (ie, using only prevalence rates among community-dwelling adolescents and adults). By updating and expanding on the data used previously to account for missing data and higher rates in these 2 populations, it is possible to calculate a high-level estimate of the total number individuals experiencing the effects of stroke in Canada, and within each region of Canada.
In addition, the previous estimate of 315 000, based on data from 2009/2010, was static and did not consider population changes over time. Our results demonstrate that, although the prevalence remained relatively consistent over 11 years of data, the number of individuals experiencing the effects of stroke rose considerably as a result of population growth, aging, and decreasing stroke mortality rates.17 In coming years, we expect that this will be an ongoing issue as the population continues to age, resulting in rising stroke prevalence. These demonstrated increases underscore the importance that estimates be continually updated to reflect this progression in future years. Indeed, when we adjusted the previous estimate of 315 000 to take recent data, population growth and changes in population distribution into consideration, the number of community-dwelling individuals experiencing the effects of stroke increased by ≈52 000 people. This value still underestimated true prevalence, however, and by expanding these prevalence rates to account for higher rates of stroke among individuals living in homes for the aged, and missing data for children aged 0 to 11 years, the number of individuals experiencing the effects of stroke increased by another 38 000.
Similar data from the Australian Survey of Disability, Aging and Carers18 captured a sample that well represents the entire Australian population, including children and those living in cared-accommodation facilities, and estimated the prevalence of stroke survivors who have long-term effects of their stroke that interfere with everyday activities. When we applied the age- and sex-specific prevalence from this survey to the Canadian population in 2013, we estimated that 455 000 (1.29%) individuals in Canada were living with the long-term effects of a stroke. Although this value is similar to the one we obtained using Canada-specific data, the differences may be accounted for by a variation in the distribution of stroke-specific risk factors. For example, obesity rates in 2013 among those aged ≥20 years in Canada were 21.9% in men and 20.5% in women, compared with 27.5% and 29.8% in the equivalent Australian populations.19 Obesity is associated with an ≈50% increase in the risk of stroke,20 therefore we would expect that stroke incidence may be higher in Australia as a result.
In other countries, the self-reported prevalence of stroke in those aged ≥65 years has been reported between 4.6% and 7.4%,21 whereas we estimated that 5.0% of this age group were experiencing the effects of stroke. In European countries, the estimated prevalence of stroke among those aged 65 to 74 years ranged from 2.4% to 14.2% for men, and from 1.5% to 9.0% for women.22 We estimated that 3.7% of men and 3.4% of women in this age group were experiencing the effects of stroke.
The Australian Survey of Disability, Aging and Carers also included questions that enable the calculation of both the number of stroke survivors and those who have long-term effects of stroke that interfere with everyday activities. From these data, the large difference between rates of stroke survivorship and rates of stroke survivorship with disability becomes clear. In fact, 37% of stroke survivors in Australia did not have ongoing effects.18 This difference draws attention to the challenge of clarifying the intended population to be included in calculating stroke prevalence. The focus of the current analysis has been on the prevalence of stroke survivors living with disability or other stroke consequences and therefore does not include stroke survivors who have experienced a full recovery. This challenge is compounded because research suggests that some individuals are left with mild cognitive disability of which they may or may not be aware. Other researchers have also shown that many individuals diagnosed with dementia have a cerebrovascular cause or contribution to their impairments.23 It would be difficult to obtain an accurate estimate of the overall prevalence of stroke survivors in Canada unless a comprehensive national survey was to ask questions similar to those that were covered by the Survey of Disability, Aging and Carers.
Projecting future trends is notoriously difficult as the future prevalence depends on changes in the incidence of stroke, improvements in treatment, increases in population, and changes in the age structure of the population. The incidence of stroke, however, is at least partially associated with the prevalence of specific risk factors. In Canada, for example, the prevalence of tobacco smoking has declined by 22% between 2000 and 2012 and physical inactivity has declined by 13%. In contrast, the prevalence of alcohol use that could be considered harmful or hazardous has increased by 28% and obesity by 17%.6 Approximately 60% of strokes are attributable to these 4 risk factors.24
We were restricted to primarily self-report data in completing this analysis. Clinical registries or medical charts are arguably the gold standard for ascertaining cases of stroke but, because of their expense, are rarely used at a population level. Using algorithms to access administrative data such as hospital, physician, and prescription drug records is an alternative approach but the results can vary substantially depending on the algorithm used.25 Comparisons between administrative data and CCHS survey results suggest a fair to moderate agreement between the 2 approaches.26,27 Our prevalence results for Canada are within the range of published results from other countries.
We were unable to incorporate information on stroke severity as these data are not routinely collected in Canada. A previous Canadian study suggested that 54.2% of those who received stroke care in Canada had scored 0, 1, or 2 on the Rankin Scale, 20.5% scored 3, and 25.3% scored 4 or 5.12
Finally, we were unable to find age and sex-specific prevalence rates of stroke in residents of homes for the aged and used instead a single estimate of 21.9% in our estimates and projections. Using age- and sex-specific rates, as we did for the noninstitutionalized population, would lead to greater precision in our projections.
Sources of Funding
This study was funded by the Heart & Stroke Foundation Canadian Partnership for Stroke Recovery.
The online-only Data Supplement is available with this article at http://stroke.ahajournals.org/lookup/suppl/doi:10.1161/STROKEAHA.115.009616/-/DC1.
- Received March 31, 2015.
- Revision received June 1, 2015.
- Accepted June 9, 2015.
- © 2015 American Heart Association, Inc.
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