We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
Application of the case-crossover design to reduce unmeasured confounding in studies of condom effectiveness.
- Authors
Warner, Lee; Macaluso, Maurizio; Austin, Harland D; Kleinbaum, David K; Artz, Lynn; Fleenor, Michael E; Brill, Ilene; Newman, Daniel R; Hook, Edward W, 3rd
- Abstract
This analysis examined how unmeasured confounding affects estimates of the effectiveness of condoms in preventing sexually transmitted infections. Data were analyzed from a prospective cohort study of 1,122 female sexually transmitted disease clinic patients in Alabama (1992-1995), wherein participants were evaluated for sexually transmitted infections at six 1-month intervals. Associations between condom use and incident gonorrhea and chlamydia infection were compared between case-crossover and cohort analyses. In a case-crossover analysis of 228 follow-up visits ending in gonorrhea/chlamydia ("case intervals") and 743 self-matched follow-up visits not ending in gonorrhea/chlamydia ("noncase intervals") (183 women), consistent condom use without breakage or slippage was associated with significantly reduced risk of infection relative to nonuse (adjusted risk odds ratio = 0.49, 95% confidence interval: 0.26, 0.92). Conversely, a cohort analysis of 245 case intervals and 3,896 noncase intervals (919 women) revealed no significant reduction in infection risk from consistent use of condoms (adjusted risk odds ratio = 0.79, 95% confidence interval: 0.53, 1.17). Dose-response relations between the number of unprotected sex acts and infection were stronger in the case-crossover analysis (p for trend = 0.009) than in the cohort analysis (p for trend = 0.18). These findings suggest that epidemiologic studies confounded by unmeasured differences between condom users and nonusers underestimate condom effectiveness against these infections. The case-crossover method provides an additional technique for reducing unmeasured confounding in studies of condom effectiveness.
- Publication
American journal of epidemiology, 2005, Vol 161, Issue 8, p765
- ISSN
0002-9262
- Publication type
Journal Article
- DOI
10.1093/aje/kwi094