Heterosexual anal intercourse among youth: A systematic review and metaanalysis

Abstract

Background: Anal intercourse (AI) is a risk factor of HIV/HPV infection and anal cancer. However, heterosexual AI practises are ill-understood. Our objective was to understand the level and heterogeneity in AI among heterosexual youth Methods: We conducted a systematic review and meta-analysis. PubMed was searched for studies reporting heterosexual AI among the general population with a mean age < 25 years published 1975-2012. Meta-analysis and meta-regression were used where appropriate to summarise estimates and test whether continent, survey year, mean age and interview method explained variation in AI prevalence among sexually active and all youth. Results: 110 eligible studies were identified from North America (n = 75), Europe (14), Africa (13), Latin America (4) and Asia (4). Studies of AI prevalence over lifetime (n = 66) and 3 months (n = 16) only are reported here. Both lifetime and three-month AI prevalence estimates were too heterogeneous to pool (I2 > 90%). Lifetime AI prevalence was 0.2%-55.7% and 0.0%-38.8% in sexually active and all youth, respectively. AI among all youth increased significantly (p= 0.05) with mean age. Among sexually active youth, interview method explained 12% and 47% of variation in AI prevalence in male/mixed gender samples, respectively. Higher prevalence was reported using more confidential methods. Lifetime prevalence increased significantly with survey year among all gender groups in Europe, but not elsewhere. Three-month AI prevalence was 5.1%-52.6% and 1.3%-22.7% in sexually active and all youth, respectively. Among all youth, mean age explained 76% and 80% of variation in female and mixed AI prevalence, respectively. Three-month prevalence increased significantly with survey year in sexually active female samples (all from North America). Conclusion: AI is common among all young heterosexual populations, with prevalence increasing in Europe and possibly among females in North America. It could therefore become an increasingly important determinant of HIV and HPV transmission.