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COMMENTS & OPINIONS
The Number Needed to Be Exposed: A Potential Use for Quantifying the Strength of an Individual Risk Factor Including a Protective Factor in a Cohort Study
Huai yong Cheng, MD, MPH
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A recent cohort study in the Archives showed that higher recreational physical activity in postmenopausal women was independently associated with low incidence of breast cancer after adjusting for multiple confounders.1 Based on the data reported by Bardia et al,1 there were 4.7 (dividing 1216 by 259 247) and 4.1 (dividing 582 by 141 180) breast cancer cases per 1000 person-years among women who had low- and high-recreational physical activity, respectively, at baseline. Compared with low-recreational physical activity, high-recreational physical activity was associated with a reduced breast cancer incidence by 0.6 per 1000 person-years (4.7 per 1000 person-years minus 4.1 per 1000 person-years). The potential limitation of such a small absolute risk reduction of breast cancer incidence related to high-recreational physical activity was not quantified and fully discussed.1 Based on the concept and calculation of the number needed to treat, "the number needed to be exposed" (NNE) was . . . [Full Text of this Article]
AUTHOR INFORMATION
RELATED LETTER
The Number Needed to Be Exposed: A Potential Use for Quantifying the Strength of an Individual Risk Factor Including a Protective Factor in a Cohort Study—Reply
James R. Cerhan, Aditya Bardia, Robert A. Vierkant, and Celine M. Vachon
Arch Intern Med. 2007;167(15):1690-1691.
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RELATED ARTICLE
Recreational Physical Activity and Risk of Postmenopausal Breast Cancer Based on Hormone Receptor Status
Aditya Bardia, Lynn C. Hartmann, Celine M. Vachon, Robert A. Vierkant, Alice H. Wang, Janet E. Olson, Thomas A. Sellers, and James R. Cerhan
Arch Intern Med. 2006;166(22):2478-2483.
ABSTRACT
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