Physical activity, but not body mass index, predicts less disability before and after stroke

Abstract

Objective: To determine whether physical activity and body mass index (BMI) predict instrumental or basic activities of daily living (I/ADL) trajectories before or after stroke compared to individuals who remained stroke-free.

Methods: Using a prospective cohort, the Health and Retirement Study, we followed adults without a history of stroke in 1998 (n = 18,117) for up to 14 years. We estimated linear regression models of I/ADL trajectories comparing individuals who remained stroke-free throughout follow-up (n = 16,264), those who survived stroke (n = 1,374), and those who died after stroke and before the next interview wave (n = 479). We evaluated whether I/ADL trajectories differed by physical activity or BMI at baseline (before stroke), adjusting for demographic and socioeconomic covariates.

Results: Compared to those who were physically active, stroke survivors who were physically inactive at baseline had a lower probability of independence in ADLs and IADLs 3 years after stroke (risk difference = -0.18 and -0.16 for ADLs and IADLs, respectively). However, a similar difference in the probability of independence was also present 3 years before stroke, and we observed no evidence that physical activity slowed the rate of decline in independence before or after stroke. Unlike the results for physical activity, we did not observe a consistent pattern for the probability of independence in ADLs or IADLs comparing obese stroke survivors to normal-weight or to overweight stroke survivors 3 years before stroke or 3 years after stroke.

Conclusions: Physical inactivity predicts a higher risk of being dependent both before and after stroke.

Figure 1. Probability of I/ADL independence by stroke status and baseline physical activity

Predicted probability of independence in all I/ADLs (an indicator of self-reported difficulty with any of the 5 individual ADLs and 5 individual IADLs) stratified by baseline physical activity status: (A) ADL, physically inactive, (B) ADL, physically active, (C) IADL, physically inactive, and (D) IADL, physically active by stroke status over follow-up (never/survivor/decedent): HRS, 1998–2012. Reference group is defined as 75-year-old, white, married women who were born in the South, whose mothers had ≤8 years of education, and who themselves had the lowest quartile of education, less than a high school education, and no comorbidities. Vertical line represents the transition at the time of stroke for stroke patients, with predicted probabilities of independence modeled for someone whose stroke occurred at age 75. Regression model point estimates and confidence intervals underlying this figure are reported in table e-2. ADL = activities of daily living; HRS = Health and Retirement Study; IADL = instrumental activities of daily living; = date of stroke (vertical line).

Figure 2. Probability of I/ADL independence by stroke status and baseline weight status

Predicted probability of independence in all I/ADLs (an indicator of self-reported difficulty with any of the 5 individual ADLs and 5 individual IADLs) stratified by weight status: (A) ADL, normal weight, (B) ADL, overweight, (C) ADL, obese, (D) IADL, normal weight, (E) IADL, overweight, and (F) IADL, obese and by stroke status over follow-up (never/survivor/decedent): HRS, 1998–2012. Reference group is defined as 75-year-old, white, married women who were born in the South, whose mothers had ≤8 years of education, who themselves had lowest quartile of education, height, and household wealth, and who had no comorbidities. Vertical line represents the transition at the time of stroke for stroke patients, with predicted probabilities of independence modeled for someone whose stroke occurred at age 75. Regression model point estimates and confidence intervals underlying this figure are reported in tables e-3 and e-4. ADL = activities of daily living; HRS = Health and Retirement Study; IADL = instrumental activities of daily living; = date of stroke (vertical line).