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Risk Factor Reversal in Studies of Infectious Disease

Making Counterintuitive Results Intuitive Again

Kaufman, Jay S., PhD*; Banack, Hailey R., PhD; Adams, Joëlla W., MPH; Marshall, Brandon D. L., PhD; Stovitz, Steven D., MD, MS§

Sexually Transmitted Diseases: January 2019 - Volume 46 - Issue 1 - p e5–e7
doi: 10.1097/OLQ.0000000000000911

A previously published study reported the seemingly paradoxical finding that men who have sex with men status was strongly protective and recent sexual abstinence strongly deleterious in relation to mortality prognosis. We explain why these results are entirely logical and that the counterintuitive direction of the effects derives from the comparison group implied by the study design.

We show that seemingly paradoxical protective effects reported for human immunodeficiency virus mortality prognosis may be due to selection bias in the study design.

From the *Department of Epidemiology, Biostatistics, and Occupational Health McGill University, Montreal, QC, Canada,

Department of Epidemiology and Environmental Health School of Public Health and Health Professions University at Buffalo, The State University of New York, Buffalo, NY,

Department of Epidemiology Brown University School of Public Health, Providence, RI, and

§Department of Family Medicine and Community Health University of Minnesota, Minneapolis, MN

Source of Funding and Conflicts of Interest: None declared.

J.S.K. theorized that the paradoxical results would occur. S.D.S. searched for and found the existing study reporting the theoretically anticipated results. J.S.K., S.D.S., and H.R.B. then drafted the article, which was reviewed, edited and improved by J.W.A. and B.D.L.M., the first and senior author of the original publication, respectively. All authors then made final edits before the article was submitted.

“Research Note”, revised for “Sexually Transmitted Diseases” Aug 22, 2018.

Correspondence: Jay S. Kaufman, PhD, Department of Epidemiology, Biostatistics, and Occupational Health 1020 Pine Ave W, Montreal, QC, Canada H3A1A2. E-mail:

Received for publication March 7, 2018, and accepted August 23, 2018.

© Copyright 2019 American Sexually Transmitted Diseases Association