LAUSR

A recent systematic review andmeta-analysis identified a significant association between rectal douching and being diagnosed with HIV (odds ratio [OR], 2.80; 95% confidence interval [CI], 2.32–3.39) or other sexually transmitted infections (STIs; OR, 2.46; 95% CI, 1.95–3.11) among men who have sex with men (MSM). Douching is widely practiced in this population, which remains at significantly higher risk of HIVand STI acquisition in many settings despite recent advances in prevention technologies. However, the nature of the association, the potential causal mechanisms, and the implications of this finding for research and practice remain uncertain. This uncertainty can be resolved by considering relevant social and behavioral perspectives in study design. The review finds that people who report douching are more likely to report positive HIVand STI diagnoses. The hypothesized causal mechanism is physical or biochemical disruption of the anorectal epithelia, which continually produce a thin film of mucus that facilitates fecal transit and mobilizes immune cells. This disruptive effect has been observed in laboratory studies of douching with plain water and with preservative ingredients used in water-based lubricants. The resulting inflammation may facilitate HIVand STI acquisition. Cautions should be taken when interpreting the association observed in the review. Douching is an act done in preparation for receptive anal intercourse, which carries greater risk of HIVacquisition than insertive sex (OR, 6.90; 95% CI, 5.50–8.60). Thus, significant collinearity between douching and receptive anal intercourse may exist. Although the review included a subanalysis of studies that undertook multivariate regression, it may not be possible to disentangle the effect of potential confounders using data from cross-sectional survey designs. The diversity of sexual cultures