To the Editor: Dr McTiernan and colleagues1 of the Women's Health Initiative (WHI) reported that increased physical activity was associated with a 14% decrease in the risk of breast cancer in postmenopausal women. These results were not based on a randomized trial of exercise vs no exercise, but rather were from observational data. An earlier randomized WHI study2 of estrogen plus progesterone therapy vs placebo demonstrated that the prior observational studies that had demonstrated a cardiovascular benefit for hormone therapy were incorrect. It was clear that there was a strong bias in the prior observational studies toward showing a cardiovascular benefit in the women who had selected the hormone replacement therapy intervention. Thus, it is possible that a similar bias occurred in this study as well.
Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature
Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
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