Harvard Women's Health Watch

Snapshots from the Women’s Health Initiative Observational Study

Almost 94,000 women are enrolled in the Women's Health Initiative Observational Study. For an average of nearly eight years, they have answered annual questionnaires about their health and activities. Based on the data, researchers have found the following:

  • Physical activity is associated with a 30%–40% reduction in risk for heart disease. Strenuous exercise and brisk walking (about one mile per 15 minutes) confer the same degree of benefit.

  • Breast cancer rates are 18% lower in women who walk briskly for 1.25–2.5 hours per week and even lower for women who briskly walk 10 hours or more per week.

  • The amount of weight gained over a lifetime is a predictor of breast cancer risk, with greater weight gains associated with greater risk. Moreover, for women who have never used hormone therapy, those who are heavier have a greater risk of getting breast cancer than those who are slimmer.

  • Physical activity lowers the risk for diabetes in white women, but the benefits aren't as clear for other racial/ethnic groups.

  • Women whose white blood cell (WBC) counts are above 6.7 have an elevated risk for cardiovascular disease, compared with women who have lower WBC counts.

  • Women who are depressed have a higher risk for cardiovascular disease than those who are not.

  • African American and Asian women are more likely to have hypertension than white or Hispanic women, and they are less likely to have their high blood pressure under control.

  • Most WHI participants report waking up several times a night or earlier than planned. Only 27% sleep 8 hours or more per night. Those sleeping 9–10 hours or 6 hours or less are more likely to be more obese and more depressed than those sleeping 7–8 hours nightly.

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