Background and purpose: Findings from the Framingham Heart Study suggest that declines in dementia incidence rates over recent decades are partially due to decreases in stroke incidence and mortality; however, whether trends of declining dementia rates extend to survivors of incident stroke remains unclear. We investigated evidence for temporal trends in memory change related to incident stroke in a nationally representative cohort.
Methods: Adults age 50+ in the HRS (Health and Retirement Study) were followed across three successive 6-year epochs (epoch 1: 1998-2004, n=16 781; epoch 2: 2004-2010, n=15 345; and epoch 3: 2010-2016; n=15 949). Participants were included in an epoch if they were stroke-free at the start of that epoch. Annual rates of change in a composite z-standardized memory score were compared using demographic-adjusted linear regression models for stroke-free participants, those who survived after stroke, and those who died after stroke, considering memory change before stroke, at the time of stroke, and for years following stroke.
Results: Crude stroke incidence rates decreased from 8.5 per 1000 person-years in epoch 1 to 6.8 per 1000 person-years in epoch 3. Rates of memory change before and following stroke onset were similar across epochs. Memory decrement immediately after stroke onset attenuated from -0.37 points (95% CI, -0.44 to -0.29) in epoch 1 to -0.26 (95% CI, -0.33 to -0.18) points in epoch 2 and -0.25 (95% CI, -0.33 to -0.17) points in epoch 3 (P value for linear trend=0.02).
Conclusions: Decreases in stroke-related dementia in recent years may be partially attributable to smaller memory decrements immediately after stroke onset. Findings suggest reductions in stroke incidence and improvements in stroke care may also reduce population burden of dementia. Further investigations into whether temporal trends are attributable to improvements in stroke care are needed.
Keywords: adult; dementia; incidence; memory; survivors.