Exercise Linked to Independence Before and After Stroke  

April 10, 2017

Physical inactivity, but not body mass index (BMI), predicts a higher risk of being dependent both before and after stroke, a new study shows.

The study, published online in Neurology on April 5, was conducted by a team led Pamela M. Rist, ScD, Brigham and Women's Hospital, Boston, Massachusetts.

Dr Rist and colleagues note that identifying modifiable factors that may ameliorate the functional consequences of stroke is a high research priority. Retrospective studies indicate that stroke patients who reported regular exercise before stroke onset have milder strokes or better functional outcomes after stroke, and there has been some suggestion of better outcomes after stroke among obese or overweight individuals.

However, they point out that most of these data have been collected retrospectively in stroke survivors and may be inaccurate because such designs cannot evaluate how functional status changed as a result of stroke: for example, whether physical activity or prestroke body mass index (BMI) modifies the change in functioning associated with stroke onset. Additionally, these studies cannot examine functioning years before stroke to determine whether differences in post-stroke functioning are driven by prestroke functioning.

To look at these issues, the researchers analyzed data from the Health and Retirement Study — a large cohort study of 18,117 individuals representative of a national cohort in the United States older than age 50 years without a history of stroke at baseline. They were asked about physical activity levels and BMI at baseline and followed for 14 years. Every 2 years, they were asked whether they had had a stroke and about their activities of daily living.

In the study, physical activity was defined as vigorous exercise (sports or heavy housework/physical labor) three times a week or more. Almost half the cohort (45%) reported achieving this level of activity at baseline.

Results showed that 16,264 individuals remained stroke-free throughout follow-up, 1374 survived a stroke, and 479 died after a stroke.

After adjusting for demographic and socioeconomic covariates, the researchers found that compared with those who were physically active, stroke survivors who were physically inactive at baseline had a lower probability of independence in activities of daily living 3 years after stroke (risk difference, –0.18 and –0.16 for activities of daily living and instrumental activities of daily living, respectively).

Instrumental activities of daily living, they note, are activities that involve more of a cognitive component, such as taking medications as prescribed, grocery shopping, using the telephone, preparing meals, and managing money.

However, a similar difference in the probability of independence was also present 3 years before stroke.

Unlike the results for physical activity, no consistent pattern for a relationship between obesity for overweight and probability of independence before or after stroke was seen.

"We found that patients who had had a stroke and survived and who were inactive at baseline were much less likely to be independent 3 years after their stroke than patients who were active at baseline," Dr Rist told Medscape Medical News. "This was to be expected based on previous knowledge."   

But they also found that these results seemed to be driven by independence before the stroke occurred, she noted. "People who are physically inactive have a reduced probability of being independent before their stroke compared to those who are active," she said. "Therefore, it appears that physical activity protects us from developing limitations in daily activities both before and after a stroke."

People who exercise are more likely to remain independent for longer regardless of whether they have a stroke or not, Dr Rist added.  "This makes sense as many activities of daily living have a physical component — getting in and out of bed, shopping, housework, et cetera.

"Our results suggest that even if you don't have a stroke you are still more likely to remain independent if you exercise regularly," she concluded.

"In contrast, we didn't find any definite relation between BMI on activities of daily living either before or after stroke. If people were overweight or obese before their stroke, this wasn't associated with less functional independence before or after their stroke. BMI does not appear to be an important predictor of the stroke disability trajectory."

Dr Rist stressed, however, that BMI is still important because it is believed to be a stroke risk factor.

The researchers point out that examining limitations to instrumental activities of daily living "adds substantially to the existing literature" and that this may be a major determinant of quality of life among stroke patients.

"Given that IADLs [instrumental activities of daily living] are more cognitively demanding…and that physical activity may help to maintain cognitive function, it is possible that physical activity before stroke may protect against IADL limitations through its effects on cognitive function," they conclude.

The study was supported by the National Institute on Aging, the American Heart Association, and the National Institute of Neurologic Disorders and Stroke. The researchers have disclosed no relevant financial relationships.

Neurology. Published online April 5, 2017. Abstract

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