MODERATING EFFECT OF BODY HEIGHT ON THE ASSOCIATION OF BODY WEIGHT AND DISABILITY CAUSED BY NON SPECIFIC CHRONIC LOW BACK PAIN IN WOMEN AND MEN.

The aim of the study was testing the hypothesis that body height has a moderating effect on the association of weight and chronic low back pain (LBP) induced disability, and that this moderating effect is different in women and men. We performed a nested cross-sectional analysis using data collected at baseline in a prospective cohort study conducted in 2008-2009 at a special hospital for medical rehabilitation in Croatia. The outcome was the Roland-Morris Disability Questionnaire (RMDQ) score. The independent variable was body weight. The focal moderators were body height and sex. The moderation analysis was adjusted for seven sociodemographic and clinical covariates. We analyzed data on 72 patients with a median (interquartile range) age of 50 (43-55) years, 36 (50%) of whom were women, treated for nonspecific, chronic LBP. The interaction of sex, body weight and height was a significant predictor of the RMDQ score after adjustments for all covariates (increase of R2=0.13; p=0.001; false discovery rate <5%). In both sexes, the correlation between body weight and the RMDQ score was significantly moderated by body height but in opposite ways. In conclusion, the effects of body weight on physical disability are moderated by body height, but this moderation effect differs between women and men.