Association between alcohol consumption and chronic pain: a systematic review and meta-analysis.

INTRODUCTION:Chronic pain represents a global health problem with a considerable economic burden. The relation of alcohol intake and chronic pain conditions was assessed in several studies with conflicting results. We used dose-response meta-analysis techniques to answer the question of whether alcohol intake is related to chronic pain occurrence. METHODS:We searched MEDLINE, Embase, and other databases to identify cohort and case-control studies on alcohol consumption and chronic pain. Sixteen studies were eligible with a total population of 642 587 individuals. Fixed-effects and random-effects pooled estimates were obtained by weighting log odds ratios (ORs) in case-control studies and log incidence rate ratios in cohort studies by the inverse of their variance. A heterogeneity assessment and a dose-response analysis were carried out. Quality scoring was also performed. RESULTS:Our results show that any alcohol consumption was related to lower odds of chronic pain (pooled OR=0.76; 95% confidence interval [CI], 0.61-0.95). The association was non-linear. The ORs by quartile of alcohol doses were as follows: OR2nd quartile=0.74; 95% CI, 0.64-0.87; OR3rd quartile=0.67; 95% CI, 0.53-0.86; and OR4th quartile=0.75; 95% CI, 0.50-1.14. This association was observed for cohort studies (OR=0.77; 95% CI, 0.61-0.98) and European studies (OR=0.65; 95% CI, 0.48-0.87) only. Studies with complete adjustment for confounding factors showed a stronger relation than those with incomplete adjustment (OR=0.69; 95% CI, 0.48-0.99 and OR=0.85; 95% CI, 0.65-1.11, respectively). CONCLUSION:Alcohol consumption presents a non-linear inverse association with the occurrence of chronic pain. Although plausible mechanisms could explain this protective effect, other explanations, including reverse causation, are probable.