Joint effect of stroke and APOE 4 on dementia risk: the Canadian Study of Health and Aging.
BACKGROUND
Although stroke and APOE 4 are independent risk factors for dementia, their combined effect remains uncertain. We assessed their joint effect on dementia risk.


METHODS
Subjects participated in Phases 1 and 2 of the Canadian Study of Health and Aging (CSHA). Dementia was diagnosed by consensus, and stroke was diagnosed by history or clinical examination. Analyses were first conducted among clinical participants only, and then rerun with the screening sample included as well.


RESULTS
Analyses included 949 participants from CSHA-1 and 1,413 from CSHA-2. During a median 4.6-year follow-up, 740 were included in the CSHA-1 to -2 incidence study. Among clinical participants, the highest prevalence (40.6% for CSHA-1 and 57.6% for CSHA-2) and incidence (8.4 per 100 person-years) of dementia occurred in elderly having both stroke and APOE 4; the lowest prevalence (19.8% for CSHA-1 and 23.3% for CSHA-2) and incidence (4.3 per 100 person-years) were among persons having neither. These findings held true when the screening sample was included. The adjusted hazard ratios of incident dementia, relative to elderly with neither stroke nor APOE 4, were 1.33 (95% CI 0.73 to 2.43) for stroke alone, 2.06 (95% CI 1.42 to 2.99) for APOE 4 alone, and 2.57 (95% CI 1.11 to 5.94) for both. No interaction on additive or multiplicative scales was suggested.


CONCLUSIONS
The joint presence of stroke and APOE 4 was associated with a greater risk of dementia compared with absence of these two factors. The effect of stroke on dementia does not seem to be modified by APOE 4.
Jin
Y P
YP
Department of Clinical Neurological Sciences, London Health Sciences Centre and University of Western Ontario, 339 Windermere Rd., London, Ontario, Canada. yaping.jin@utoronto.ca
Østbye
T
T
Feightner
J W
JW
Di Legge
S
S
Hachinski
V
V
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D053327:Apolipoprotein E4; D002170:Canada / Q000453:epidemiology; D003704:Dementia / Q000150:complications / Q000453:epidemiology / Q000235:genetics; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D016017:Odds Ratio; D015995:Prevalence; D012189:Retrospective Studies; D012307:Risk Factors; D020521:Stroke / Q000150:complications / Q000453:epidemiology / Q000235:genetics
D053327:Apolipoprotein E4