Dementia and stroke comorbidity among Canadians aged 65 years and older

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Organization: Public Health Agency of Canada

Published: 2020-09-18

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Highlights from the Canadian Chronic Disease Surveillance System

DementiaFootnote i and stroke are common and debilitating chronic conditions in Canada. They pose significant health challenges, especially among individuals aged 65 years and older. The risk of developing these conditions, either separately or together (i.e. comorbidity), increases with age.Footnote 1 Footnote 2 Footnote 3 Some Canadian studies have investigated comorbid dementia and stroke in specific populations;Footnote 4 Footnote 5 however, there are insufficient data to estimate the prevalence of this comorbidity in the general Canadian population.Footnote 6 Footnote 7

This factsheet provides new estimates on dementia and stroke comorbidity among Canadians aged 65 years and older, examining the simultaneous presence of dementia and any stroke using data from the Canadian Chronic Disease Surveillance System (CCDSS). The Public Health Agency of Canada (PHAC) uses the CCDSS to conduct national surveillance of 20 chronic conditions, including diagnosed dementia and stroke.Footnote 8 Footnote 9

Dementia refers to a set of symptoms and signs associated with a progressive deterioration of cognitive functions that affect daily activities.Footnote 8 It is caused by various diseases and injuries in the brain and vascular system. Alzheimer's disease represents the most common cause of dementia, while vascular dementia is the second most common cause of dementia. However, evidence suggests that mixed dementia, involving any combination of causes but often these two, is also common.Footnote 10 Footnote 11

A stroke is a sudden loss of brain function caused by a brain blood vessel blockage (ischemic stroke) or rupture (haemorrhagic stroke).Footnote 9

Validated case definitions for diagnosed dementiaFootnote 12 in individuals aged 65 years and older, and diagnosed strokeFootnote 13 in individuals aged 20 years and older, were applied to CCDSS longitudinal data (i.e., April 1, 1996 to March 31, 2017). Among individuals aged 65 years and older still alive in 2016–2017, coexisting dementia and stroke cases (regardless of the order of occurrence) were identified as prevalent comorbid cases. Data are presented for fiscal year 2016–2017. Data from all Canadian provinces and territories, except Saskatchewan, were available for these analyses.

How many Canadians aged 65 years and older have both dementia and stroke (prevalence)?

According to 2016–2017 fiscal year data from the CCDSS, 6.9% (or 432,000) of individuals 65 years and older were living with dementia and 9.6% (or 602,000) had a stroke since the beginning of the surveillance period in 1996–1997. Overall, in the population aged 65 years and older:

In 2016–2017, about 1.8% (or 110,000) of individuals aged 65 years and older were living with comorbid dementia and stroke, while 5.1% (or 322,000) were living with dementia, without a stroke, and 7.8% (or 492,000) had a stroke, without dementia (Table 1).

Table 1

Crude prevalence (%) of dementia and stroke in individuals aged 65 years and older, Canada*, 2016–2017
Population Crude prevalence, %
Individuals with dementia and stroke 1.8
Individuals with dementia, without stroke 5.1
Individuals with stroke, without dementia 7.8
Individuals without dementia and stroke 85.3

Crude rates were based on randomly rounded counts to an adjacent multiple of 10.

*Data from Saskatchewan were not available.

Source: Public Health Agency of Canada, using Canadian Chronic Disease Surveillance System data files contributed by provinces and territories, August 2019.

The prevalence of dementia and stroke comorbidity was greater in women than men (1.9% vs. 1.6%) using crude rates; however, this pattern is reversed when using age–standardized rates (1.6% vs. 1.8%) given the age distribution of the senior population.

The prevalence of dementia without stroke increased with age. Women 75 years and older had a higher prevalence of dementia without stroke than men of the same age (Table 2a). The prevalence of stroke without dementia also increased with age, although it increased less rapidly after the age of 85. Regardless of age, stroke without dementia occurred more frequently in men than women (Table 2b).

Table 2

Crude prevalence (%) of individuals aged 65 years and older (a) living with dementia, without stroke and (b) who have had a stroke, without dementia, by age group and sex, Canada*, 2016–2017
Age Group (Years) 2a. Dementia, without stroke  
Crude prevalence, % 
(95% Confidence Interval)
2b. Stroke, without dementia
Crude Prevalence, % 
(95% Confidence Interval)
Women Men Total Women Men Total
65–69 0.6 (0.6-0.6) 0.6 (0.6-0.6) 0.6 (0.6-0.6) 4.0 (4.0-4.0) 5.3 (5.3-5.4) 4.6 (4.6-4.7)
70–74 1.9 (1.9-1.9) 1.7 (1.7-1.7) 1.8 (1.8-1.8) 5.7 (5.6-5.7) 7.5 (7.4-7.6) 6.6 (6.5-6.6)
75–79 4.7 (4.6-4.8) 4.0 (3.9-4.0) 4.4 (4.3-4.4) 7.8 (7.7-7.8) 9.9 (9.9-10.0) 8.8 (8.7-8.8)
80–84 9.8 (9.7-9.9) 7.8 (7.8-7.9) 8.9 (8.9-9.0) 9.9 (9.8-10.0) 12.5 (12.4-12.7) 11.1 (11.0-11.1)
85–89 16.7 (16.6-16.9) 12.9 (12.8-13.1) 15.2 (15.1-15.3) 11.8 (11.6-11.9) 14.4 (14.2-14.5) 12.8 (12.7-12.9)
90+ 24.7 (24.5-24.9) 18.0 (17.8-18.3) 22.7 (22.5-22.8) 12.6 (12.4-12.7) 15.0 (14.8-15.2) 13.3 (13.2-13.4)

Crude rates were based on randomly rounded counts to an adjacent multiple of 10.

*Data from Saskatchewan were not available.

Note: The 95% confidence interval shows an estimated range of values that is likely to include the true prevalence 19 times out of 20.

Source: Public Health Agency of Canada, using Canadian Chronic Disease Surveillance System data files contributed by provinces and territories, August 2019.

The prevalence of dementia and stroke comorbidity among individuals aged 65 years and older markedly increased from 0.2% in individuals aged 65 to 69 years old to 8.9% in those aged 90 years and older (Table 3). The crude prevalence of dementia and stroke comorbidity was greater in males until 90 years of age, where the crude prevalence was greater in women (9.1%) than men (8.3%). This sex pattern observed in the crude rates may be explained by the greater number of women than men surviving to the oldest age groups.

Table 3

Crude prevalence (%) of dementia and stroke comorbidity in individuals aged 65 years and older, by age group and sex, Canada*, 2016–2017
Age group (Years) Crude prevalence, % (95% Confidence Interval)
Women Men Total
65–69 0.1 (0.1-0.1) 0.2 (0.2-0.2) 0.2 (0.2-0.2)
70–74 0.4 (0.4-0.5) 0.6 (0.6-0.6) 0.5 (0.5-0.5)
75–79 1.2 (1.1-1.2) 1.5 (1.4-1.5) 1.3 (1.3-1.3)
80–84 2.8 (2.7-2.8) 3.1 (3.1-3.2) 2.9 (2.9-3.0)
85–89 5.4 (5.3-5.5) 5.6 (5.5-5.7) 5.5 (5.4-5.5)
90+ 9.1 (9.0-9.2) 8.3 (8.2-8.5) 8.9 (8.8-9.0)

Crude rates were based on randomly rounded counts to an adjacent multiple of 10.

*Data from Saskatchewan were not available.

Note: The 95% confidence interval shows an estimated range of values that is likely to include the true prevalence 19 times out of 20.

Source: Public Health Agency of Canada, using Canadian Chronic Disease Surveillance System data files contributed by provinces and territories, August 2019.

What are the mortality rates (due to any cause of death) among Canadians aged 65 years and older with dementia and stroke?

As expected, all-cause mortality rates increased with age regardless of the disease combination and were higher among older men than older women (Table 4). Overall, the age–standardized all–cause mortality rate was 6.9 times greater in individuals aged 65 years and older with both conditions compared to those without the two conditions (150.5 per 1,000 vs. 21.8 per 1,000). The age–standardized rate ratio was higher among women (7.8) than among men (6.1) (data not shown).

All–cause mortality rates were higher in persons with stroke/without dementia, persons with dementia/ without stroke and persons with both conditions when compared to persons without dementia and stroke. However, the rate ratios decreased with age, which may be explained by the increase in general mortality. As people age, they are more likely to die of any cause.

In individuals living with dementia, without stroke (Table 4a), rate ratios were similar between sexes across all age groups, except in the youngest. Rate ratios among those who had a stroke, without dementia (Table 4b) and those living with dementia and stroke comorbidity (Table 4c) were greater in women than men for all age groups, except the oldest.

Table 4

Crude all–cause mortality rates and rate ratios in individuals aged 65 years and older (a) living with dementia, without stroke, (b) who have had a stroke, without dementia and (c) living with dementia and stroke comorbidity, compared to those without dementia and stroke comorbidity, by age group and sex, Canada*, 2016–2017.

Table 4a: With dementia, without stroke
Age group (Years) Mortality rate, per 1,000
(95% Confidence Interval)
Rate ratio:
with dementia/without stroke vs.
without dementia and stroke
(95% Confidence Interval)
Women Men Women Men
65–69 64.5 (58.4-71.0) 77.7 (70.6-85.4) 9.4 (8.5-10.4) 7.1 (6.5-7.8)
70–74 67.2 (63.1-71.4) 89.1 (84.0-94.5) 6.5 (6.1-6.9) 5.7 (5.4-6.1)
75–79 79.0 (75.7-82.4) 111.2 (106.6-116.0) 5.1 (4.9-5.4) 4.7 (4.5-4.9)
80–84 100.4 (97.4-103.5) 143.0 (138.6-147.6) 4.2 (4.0-4.3) 3.9 (3.7-4.0)
85–89 138.7 (135.6-141.9) 197.5 (192.3-202.9) 3.5 (3.4-3.6) 3.3 (3.2-3.4)
90+ 227.2 (223.5-231.0) 288.8 (281.5-296.3) 2.6 (2.5-2.7) 2.7 (2.6-2.8)
Table 4b: With stroke, without dementia
Age group (Years) Mortality rate, per 1,000
(95% Confidence Interval)
Rate ratio:
with stroke/without dementia vs.
without dementia and stroke
(95% Confidence Interval)
Women Men Women Men
65–69 30.7 (29.1-32.5) 38.0 (36.3-39.7) 4.5 (4.2-4.8) 3.5 (3.3-3.6)
70–74 36.3 (34.6-38.1) 44.6 (42.9-46.4) 3.5 (3.3-3.7) 2.9 (2.7-3.0)
75–79 47.0 (45.0-49.1) 56.1 (54.1-58.3) 3.1 (2.9-3.2) 2.4 (2.3-2.5)
80–84 61.2 (58.8-63.5) 77.5 (74.9-80.2) 2.5 (2.4-2.7) 2.1 (2.0-2.2)
85–89 88.6 (85.7-91.7) 109.5 (105.8-113.3) 2.2 (2.1-2.3) 1.8 (1.7-1.9)
90+ 162.8 (158.5-167.3) 184.6 (178.2-191.2) 1.9 (1.8-1.9) 1.7 (1.6-1.8)
Table 4c: With dementia and stroke comorbidity
Age group (Years) Mortality rate, per 1,000
(95% Confidence Interval)
Rate ratio:
with dementia and stroke vs.
without dementia and stroke
(95% Confidence Interval)
Women Men Women Men
65–69 115.9 (98.7-135.4) 127.0 (111.4-144.1) 16.9 (14.5-19.8) 11.6 (10.2-13.2)
70–74 108.9 (98.2-120.4) 129.8 (119.4-141.0) 10.5 (9.5-11.7) 8.4 (7.7-9.1)
75–79 141.6 (132.7-150.9) 154.1 (145.2-163.3) 9.2 (8.6-9.8) 6.5 (6.1-6.9)
80–84 156.2 (149.2-163.4) 196.5 (188.3-205.0) 6.5 (6.2-6.8) 5.4 (5.1-5.6)
85–89 199.9 (193.3-206.7) 249.6 (240.7-258.7) 5.0 (4.8-5.2) 4.1 (4.0-4.3)
90+ 285.0 (278.2-292.0) 333.7 (322.1-345.5) 3.3 (3.2-3.4) 3.1 (3.0-3.2)

Crude rates were based on randomly rounded counts to an adjacent multiple of 10.

*Data from Saskatchewan were not available.

Note: The 95% confidence interval shows an estimated range of values that is likely to include the true prevalence 19 times out of 20.

Source: Public Health Agency of Canada, using Canadian Chronic Disease Surveillance System data files contributed by provinces and territories, August 2019.

What are the risk factors associated with dementia and stroke?

Many factors are associated with the development and progression of dementia, or having a stroke. Non–modifiable risk factors for developing dementia or stroke include age, sex, family history and ethnicity.Footnote 10 Footnote 14 Footnote 15 Footnote 16

Lifestyle factors, such as healthy eating, physical activity, limiting excessive alcohol intake and smoking cessation, can be protective in delaying or reducing the risk of dementia or stroke.Footnote 10 Footnote 14 Footnote 15 Footnote 16 Further, having a secondary school education and being socially engaged has been shown to be protective against dementia.Footnote 10 Footnote 16 Conditions like hypertension, elevated blood cholesterol, obesity, diabetes, depression, atrial fibrillation and other cardiac conditions are associated with a higher likelihood of developing dementia or having a stroke.Footnote 14 Footnote 15 Footnote 16 Footnote 17 Footnote 18

There are multiple interactions between dementia and stroke that are not yet fully understood. Similarities in their modifiable risk factors, in particular hypertension which is highly prevalent and involved in the development of both conditions, may provide insight into potential strategies to prevent or delay the development or progression of both conditions.Footnote 19 Footnote 20

What's in the data?

The data used in this publication are from the Canadian Chronic Disease Surveillance System (CCDSS), a collaborative network of provincial and territorial chronic disease surveillance systems, led by the Public Health Agency of Canada (PHAC). The CCDSS identifies chronic disease cases from provincial and territorial administrative health databases, including physician billing claims, hospital discharge abstract records, and drug prescription records linked to provincial and territorial health insurance registry records using a unique personal identifier. Data on all residents eligible for provincial or territorial health insurance are captured in the health insurance registries. Data from Saskatchewan were not available for these analyses.

Definition of dementia, including Alzheimer's disease, in the CCDSS

Canadians aged 65 years and older are identified as having diagnosed dementia, including Alzheimer's disease, if they have: at least one hospitalization record or at least three physician claims in a two-year period (with at least 30 days between each claim) with an ICD–9 or ICD–10 code for dementia, including Alzheimer's disease; or at least one anti–dementia prescription drug record.

Definition of diagnosed stroke in the CCDSS

Canadians aged 20 years and older are identified as having had a stroke if they have: at least one hospitalization record or at least two physician claims in one year with an ICD–9 or ICD–10 code for a stroke. Data presented in this publication are limited to individuals aged 65 years and older.

For more information on CCDSS disease case definitions, please visit: CCDSS disease case definitions.

Related links

Data

A dementia strategy for Canada: Together we aspire

The national dementia strategy has three objectives: prevent dementia; advance therapies and find a cure; and improve the quality of life of people living with dementia and caregivers. Surveillance and data is one of the five pillars supporting these objectives. Advancing surveillance of dementia and its comorbidities will offer a more accurate picture of their impact in Canada.

To learn more about the Strategy visit A Dementia Strategy for Canada: Together We Aspire.

Acknowledgements

This work was made possible through collaboration between PHAC and all Canadian provincial and territorial governments and expert contributions from the CCDSS Neurological Conditions Working Group and the CCDSS Stroke Working Group. This fact sheet was developed by PHAC; no endorsement by the provinces and territories is intended or should be inferred.

Notes

Footnote i

The term "dementia" includes all types of dementia, even when not specifically mentioned.

Return to footnote i referrer

References

Footnote 1

Leys D, Hilde H, Mackowiak–Cordoliani A–M, Pasquier F. Poststroke dementia. Lancet Neurol. 2005;4:752–759.

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Footnote 2

Pendlebury ST, Rothwell PM. Prevalence, incidence, and factors associated with pre–stroke and post stroke dementia: A systematic review and meta–analysis. Lancet Neurol. 2009;8:1006–1018.

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Footnote 3

Pendlebury ST. Stroke–related dementia: Rates, risk factors and implications for future research. Maturitas. 2009;64:165–171.

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Footnote 4

Jin Y–P, Di Legge S, Ostbye T, Feightner JW, Hachinski V. The reciprocal risks of stroke and cognitive impairment in an elderly population. Alzheimer's & Dementia. 2006;2:171–178.

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Footnote 5

Zerna C, Lindsay MP, Fang J, Swartz RH, Smith EE. Outcomes in hospitalized ischemic stroke patients with dementia on admission: a population–based cohort study. Can J Neurol Sci. 2018;45:290–294.

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Footnote 6

Heart and Stroke Foundation. (Dis)connected: How unseen links are putting us at risk [Internet]. Ottawa (ON): Heart and Stroke Foundation; [2019 Feb 7; cited 2019 Dec 18]. Available from: https://www.heartandstroke.ca/articles/report-2019.

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Footnote 7

Cerasuolo JO, Cipriano LE, Sposato LA, Kapral MK, Fang J, Gill SS, et al. Population–based stroke and dementia incidence trends: age and sex variations. Alzheimer's & Dementia. 2017;13:1081–1088.

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Footnote 8

Public Health Agency of Canada. Dementia in Canada [Internet]. Ottawa (ON): Public Health Agency of Canada; [2017 Sept 21; cited 2019 Oct 3]. Available from: https://www.canada.ca/en/public-health/services/publications/diseases-conditions/dementia-highlights-canadian-chronic-disease-surveillance

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Footnote 9

Public Health Agency of Canada. Stroke in Canada: Highlights from the Canadian Chronic Disease Surveillance System [Internet]. Ottawa (ON): Public Health Agency of Canada; [2017 Sept 19; cited 2019 Oct 3]. Available from: https://www.canada.ca/en/public-health/services/publications/diseases-conditions/stroke-canada-fact-sheet

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Footnote 10

Livingston G, Sommerlad A, Orgeta V, Costafreda SG, Huntley J, Ames D, et al. Dementia prevention, intervention, and care. Lancet. 2017;390(10113):2673-2734.

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Footnote 11

Vargas-González J-C, Hachinski V. Insidious cerebrovascular disease-the uncool iceberg. JAMA Neurology [Internet]. 2019 [cited 2020 Jan 15]. Available from: https://jamanetwork.com/journals/jamaneurology/article-abstract/2755282.

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Footnote 12

Jaakkimainen R, Bronskill S, Tierney M, Herrmann N, Green D, Young J, et al. Identification of physician–diagnosed Alzheimer's disease and related dementias in population–based administrative data: A validation study using family physicians' electronic medical records. J Alzheimers Dis. 2016;54(1):337–49.

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Footnote 13

Tu K, Wang M, Young J, Green D, Ivers NM, Butt D, Jaakkimainen L, Kapral MK. Validity of administrative data for identifying patients who have had a stroke or transient ischemic attack using EMRALD as a reference standard. Can J Cardiol. 2013 Nov;29(11):1388–94.

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Footnote 14

Boehme AK, Esenwa C, Elkind MS. Stroke Risk Factors, Genetics, and Prevention. Circ Res. 2017 Feb 3; 120(3):472–495.

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Footnote 15

O'Donnell MJ, Chin SL, Rangarajan S, Xavier D, Liu L, Rao–Melacini P, et al. Global and regional effects of potentially modifiable risk factors associated with acute stroke in 32 countries (INTERSTROKE): a case–control study. Lancet. 2016 Aug;388(10046):761–75.

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Footnote 16

World Health Organization. Risk reduction of cognitive decline and dementia: WHO guidelines [Internet]. Geneva: World Health Organization; [2019; cited 2019 Oct 3]. Available from: https://www.who.int/mental_health/neurology/dementia/guidelines_risk_reduction/en/.

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Footnote 17

Islam MM, Poly TN, Walther BA, Yang H–C, Wu, CC, Lin M–L, et al. Association between atrial fibrillation and dementia: a meta–analysis. Front. Aging Neurosci. 2019;11(305).

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Footnote 18

O'Donnell MJ, Xavier D, Liu L, Zhang H, Chin SL, Rao–Melacini P, et al. Risk factors for ischemic and intracerebral haemorrhagic stroke in 22 countries (the INTERSTROKE study) : a case–control study. Lancet. 2010;376:112–123.

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Footnote 19

Hachinski V, Einhäuplb K, Ganten D, Alladi S, Brayne C, Stephan BCM, et al. Preventing dementia by preventing stroke: The Berlin manifesto. Alzheimer's & Dementia. 2019;15:961–984.

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Footnote 20

Faraco G, Iadecola C. Hypertension: a harbinger of stroke and dementia. Hypertension. 2013;62(5).

Return to footnote 20 referrer

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