Changes in memory before and after stroke differ by age and sex, but not by race

Abstract

Background: Post-stroke memory impairment is more common among older adults, women and blacks. It is unclear whether post-stroke differences reflect differential effects of stroke per se or differences in prestroke functioning. We compare memory trajectories before and after stroke by age, sex and race.

Methods: Health and Retirement Study participants aged ≥50 years (n = 17,341), with no stroke history at baseline, were interviewed biennially up to 10 years for first self- or proxy-reported stroke (n = 1,574). Segmented linear regression models were used to compare annual rates of memory change before and after stroke among 1,169 stroke survivors, 405 stroke decedents and 15,767 stroke-free participants. Effect modification was evaluated with analyses stratified by baseline age (≤70 vs. >70), sex and race (white vs. nonwhite), and using interaction terms between age/sex/race indicators and annual memory change.

Results: Older (>70 years) adults experienced a faster memory decline before stroke (-0.19 vs. -0.10 points/year for survivors, -0.24 vs. -0.13 points/year for decedents, p < 0.001 for both interactions), and among stroke survivors, larger memory decrements (-0.64 vs. -0.26 points, p < 0.001) at stroke and faster memory decline (-0.15 vs. -0.07 points/year, p = 0.003) after stroke onset, compared to younger adults. Female stroke survivors experienced a faster prestroke memory decline than male stroke survivors (-0.14 vs. -0.10 points/year, p < 0.001). However, no sex differences were seen for other contrasts. Although whites had higher post-stroke memory scores than nonwhites, race was not associated with rate of memory decline during any period of time; i.e. race did not significantly modify the rate of decline before or after stroke or the immediate effect of stroke on memory.

Conclusions: Older age predicted worse memory change before, at and after stroke onset. Sex and race differences in post-stroke memory outcomes might be attributable to prestroke disparities, which may be unrelated to cerebrovascular disease.

Figure 1

Trajectory of memory decline for stroke survivors, stroke decedents and stroke-free participants by age, sex and race Predicted trajectories of memory scores for stroke survivors (n=1,169), stroke decedents (n=405) and stroke-free cohort members (n=15,767). Figure 1a (top panel) compares memory trajectories for participants ≤70 years old (dashed line) and >70 years old at baseline (solid line); Figure 1b (middle panel) compares memory trajectories for females (dashed line) and males (solid line); Figure 1c (bottom panel) compares memory trajectories for white participants (dashed line) and nonwhite participants (solid line). For Figure 1a, Time 0 indicates the time of stroke onset for participant who experienced stroke (centered at age 65 if participants were ≤70 at baseline or at age 75 if they were >70 at baseline), whereas for stroke-free participants, it represents age 65 years for those ≤70 at baseline or age 75 for those >70 at baseline. For Figure 1b and 1c, Time 0 indicates the time of stroke onset for participants who experienced stroke (centered at 70 years old), while it represents age 70 for stroke-free cohort members. Decline at stroke onset indicates the immediate decrement of memory scores at stroke onset among stroke survivors. The curves to the left of stroke onset indicate change in memory scores before stroke onset and the curve to the right indicates the change after stroke onset.