Overadjustment in regression analyses: Considerations when evaluating relationships between body mass index, muscle strength, and body size

摘要

We are writing in response to the article published in your journal by Stenholm and colleagues entitled 'Association between obesity history and hand grip strength in older adults-exploring the roles of inflammation and insulin resistance as mediating factors'. J Gemntol A Biol Sci Med Sci. 2011;66A(3):341-348.This article explores the association between obesity, defined as body mass index (BMI) >30 kg/m2, and hand grip strength. The authors report that obese men and women (n = 2,021) had lower grip strength than nonobese participants. Additionally, using recall of past weight to retrospectively calculate BMI across adulthood, a dose-response association was observed between longer obesity duration and lower grip strength. These results conflict with those of other groups who have not reported inverse associations between BMI and grip strength (1,2). However, all linear regression analyses in Stenholm's article were adjusted for body weight, to account for differences in muscle strength associated with increasing body size. Logistic regression models were also adjusted for body weight by virtue of the relative outcome measure used (grip strength/weight).