Physical Activity and the Risk for Heart Disease and Stroke in Women with Diabetes

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The summary below is from the full report titled "Physical Activity and Risk for Cardiovascular Events in Diabetic Women." It is in the 16 January 2001 issue of Annals of Internal Medicine (volume 134, pages 96-105). The authors are FB Hu, MJ Stampfer, C Solomon, S Liu, GA Colditz, FE Speizer, WC Willett, and JE Manson.

What is the problem and what is known about it so far?

Type 2 diabetes mellitus (adult-onset diabetes) is a common disease that interferes with the body's ability to store nutrients, resulting in high blood levels of sugar. Over time, high blood sugar levels can lead to complications such as blindness, kidney failure, and heart disease. Exercise helps to control blood sugar, lower blood pressure and cholesterol levels, and prevent weight gain. Physically fit men with type 2 diabetes apparently live longer than those who are less fit. It is not known, however, whether physically active women with type 2 diabetes suffer fewer heart attacks and strokes than women who are inactive.

Why did the researchers do this particular study?

To find out whether the risk for heart disease and strokes is lower in physically active women with type 2 diabetes than in those who are inactive.

Who was studied?

The study included 5125 female nurses with type 2 diabetes, but no previous history of heart disease or stroke, who were participating in a large study of women's health issues.

How was the study done?

Every 2 years for 14 years, women in the study completed a survey about health behaviors, including physical activity and medical history. Each survey asked if heart disease or stroke had occurred since the previous survey. When women reported heart disease or a stroke, the researchers obtained medical records to confirm the event. The researchers classified the amount of moderate or vigorous physical activity reported by each woman, ranging from an average of less than 1 hour to 7 or more hours per week. For women who reported no vigorous activity, the researchers collected information on usual walking pace, ranging from easy (< 2 miles per hour) to brisk (3 or more miles per hour).

What did the researchers find?

Over 14 years, 225 women developed heart disease and 98 experienced a stroke. Episodes of cardiovascular illness decreased as the amount of reported physical activity increased. Non–physically active women who reported a brisk usual walking pace had fewer cardiovascular events than slower walkers.

What were the limitations of the study?

This study included only women, so it is not known whether the relationship between activity and cardiovascular events found in this study would also be found in men with type 2 diabetes. The researchers relied on women's own reports of activity levels, which may not be accurate. While the results suggest that women with type 2 diabetes may suffer fewer cardiovascular events if they exercise actively, only a study that randomly assigns people to exercise or no exercise would prove this.

What are the implications of the study?

Physical activity, including walking, seems to reduce the risk for heart disease and stroke in women with type 2 diabetes.