Katherine M. Flegal, PhD
Potential Conflicts of Interest: None disclosed. Forms can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=L14-0024.
Flegal KM. Metabolically Healthy Overweight and Obesity. Ann Intern Med. 2014;160:515-516. doi: 10.7326/L14-5007-6
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Published: Ann Intern Med. 2014;160(7):515-516.
Kramer and colleagues (1) took data from observational studies, calculated new unadjusted RRs, and summarized the unadjusted risks. All of the summarized studies had published RRs that were adjusted for confounding factors, such as age and sex. Kramer and colleagues did not use those published RRs but instead calculated new unadjusted RRs for each study from counts of sample sizes and events. As a result, the unadjusted RRs for individual studies in this review do not match those published in the original studies.
The differences are sometimes large. For example, Kramer and colleagues included results from a study by Kuk and Ardern (2) that used data from NHANES III (the Third National Health and Nutrition Examination Survey), a complex sample survey. The original publication presented hazard ratios that were adjusted for age, sex, income, ethnicity, smoking status, and alcohol consumption and that incorporated sample weights. Kuk and Ardern found RRs of 1.24 for metabolically unhealthy normal-weight participants and 0.45 for metabolically healthy overweight participants relative to metabolically healthy normal-weight participants. The corresponding unadjusted RRs for that study that Kramer and colleagues provided were 2.52 and 0.96, respectively, but were not adjusted for the complex sample design or for any confounding factors, not even age.
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