Effect of Incident Stroke on Dementia Risk Over 10 Years in a Cohort of Asian American and Non-Latino White Older Adults in California.

Background And Objectives: Limited evidence exists on stroke incidence and its impact on dementia risk in Asian American older adults, a population with lower dementia risk than other racial and ethnic groups. We aimed to estimate the cumulative incidence of stroke and assess its effect on dementia risk over 10 years among Chinese, Filipino, Japanese, South Asian, and non-Latino White older adults in Northern California.

Methods: This cohort study included Kaiser Permanente Northern California members who participated in surveys between 2002 and 2009 with linked electronic health record data through 2020. We included Chinese, Filipino, Japanese, South Asian, and non-Latino White participants aged 60-89 years without history of stroke or dementia at the time of survey (baseline). Incident stroke and incident dementia were identified using International Classification of Diseases codes. We estimated the cause-specific cumulative incidence of stroke at 10 years of follow-up using the Aalen-Johansen estimator. We estimated the effect of incident stroke on dementia risk with risk ratios and risk differences from a weighted Kaplan-Meier survival estimator. We used time-varying inverse probability weights to adjust for confounding and censoring due to loss to follow-up and death. In secondary analyses, we restricted the exposure to ischemic stroke.

Results: We included 147,986 participants (Chinese [n = 6,034], Filipino [n = 4,649], Japanese [n = 3,099], South Asian [n = 996], non-Latino White [n = 133,208]); the mean baseline age ranged from 69 to 72 years, and the percentage of female participants ranged from 40% to 63% across groups. The 10-year cumulative incidence of stroke (95% CIs) ranged from 10.7% (9.9%-11.6%) for Chinese participants to 13.7% (12.4%-15.2%) for Japanese participants. Risk ratios relating incident stroke and dementia risk at 10 years of follow-up were 4.3 (3.0-6.4) for Chinese participants, 3.3 (2.2-4.6) for Filipino participants, 4.6 (2.5-6.6) for Japanese participants, 5.4 (1.5-12.4) for South Asian participants, and 2.9 (2.7-3.2) for non-Latino White participants. Restricting analyses to ischemic stroke yielded similar results.

Discussion: Stroke incidence is high among Asian American and non-Latino White older adults and is associated with increased dementia risk in all groups. Future research needs to disentangle the pathophysiologic mechanisms involved in the acute event of stroke that trigger and accelerate dementia onset.