SAN DIEGO—Women have a higher risk of stroke and higher rates of stroke-related disability and death compared with men, but regularly engaging in physical activity can reduce their risk by 20% to 30%, according to research presented at the 2014 International Stroke Conference. Moderate exercise, such as brisk walking, golf, or softball, may yield a greater reduction in risk of ischemic stroke than strenuous exercise, such as running, aerobics, or racquetball.
The results, which also show that regular physical activity can mitigate the increased risk of stroke associated with hormone replacement therapy (HRT), are from the California Teachers Study (CTS), reported Sophia S. Wang, PhD, Professor in the Department of Population Sciences at the Beckman Research Institute of City of Hope, Duarte, California. CTS is a prospective cohort study started in 1995 in which nearly 133,500 female teachers and administrators are enrolled.
Every four to five years, participants receive a questionnaire asking about various risk factors and their lifestyle and behaviors within the past three years. The findings on stroke risk are based on responses to the questionnaires at baseline (1995–1996) and 10 years later (2005–2006), as well as stroke data from California hospitalization records from 1995 to 2010. In that period, CTS participants had 2,416 ischemic and 710 hemorrhagic strokes.
Based on responses to the earlier questionnaire, risk reduction associated with moderate exercise was “roughly 20%,” said Dr. Wang. The reduction was greatest for those who reported engaging in moderate physical activity between 3.51 and five hours per week (relative risk [RR], 0.78).
The data were less robust for strenuous activity (RR, 0.82 for 3.51 to five hours per week). But because it can be difficult to distinguish between moderate and strenuous activity and most women who engage in strenuous activity also engage in moderate activity, “we combined the two categories,” said Dr. Wang. The result: “A quite robust decrease in risk, again about 20%, which we know now is driven largely by the moderate activity reported at baseline,” she commented.
The 2005–2006 data revealed an even greater reduction in risk of ischemic stroke from regular physical activity (RR, 0.71 for more than 3.5 hours of moderate or strenuous exercise per week). But instead of the 15 years of stroke data associated with the baseline questionnaire, Dr. Wang pointed out, the latter had only about five years of follow-up. “So there are fewer strokes, but that robust association goes from 20% to 30%.”
The mitigating effect of regular physical activity on women’s increased risk of ischemic stroke associated with HRT was found in current and former users. Menopausal women reporting more than 3.5 hours of moderate or strenuous activity per week had the greatest risk reduction (RR, 1.05 for former users and 1.29 for current users, compared with an RR of 1.16 and 1.42, respectively, for reference groups).
The strengths of the CTS stroke reduction study are its large cohort, extensive database, and use of statistical models adjusted for clinical and behavioral risk factors. Its main limitation is that physical activity was measured by self-report.
“However, it is well known that most people overestimate the amount of physical activity that they engage in,” Dr. Wang noted, “which makes our study particularly robust.”