Study design: A systematic review of the epidemiologic literature.
Objective: To establish if body weight is truly associated with low back pain (LBP) and whether the link may be causal.
Summary of background data: Because obesity and LBP are prevalent in western society, it is of interest to establish whether obesity can induce LBP.
Methods: Fifty-six original research reports, reporting on 65 studies published between 1965 and 1997, were systematically reviewed for the frequency of positive associations between body weight and LBP. In addition, the presence of positive findings was examined in relation to several study characteristics. Based on these results, only studies emanating from the general population with a sample size exceeding 3000 were included in the additional search for causality using some of the classical Bradford-Hill criteria. The review was carried out by the author, blindly at 2 months' interval.
Results: Thirty-two percent of all the studies report a statistically significant positive weak association between body weight and LBP. Studies that fulfilled the post hoc criteria never report a rate ratio above 2, but there is possibly a positive biological gradient. These studies had no information on temporality or reversibility and there was no obvious consistency of findings.
Conclusions: Due to lack of evidence, body weight should be considered a possible weak risk indicator, but there is insufficient data to assess if it is a true cause of LBP.