Environmental exposures and male infertility

Abstract

Current studies exploring the association between male infertility and environmental exposures are limited due to inadequate sample sizes, descriptive designs and/or improper control group selection. In addition, while various environmental factors have been associated with detrimental affects on semen parameters, it is unclear whether such factors actually impair the ability of a man to father a child. The aim of this study was to determine whether environmental exposures are associated with male infertility, and to examine the strength of association between environmental exposures on male factor compared to unexplained infertility cases. Retrospective Case-Control This study was performed using data previously collected as part of a large multi-center trial (Reproductive Medicine Network) in which both infertile and fertile couples were recruited from university-based infertility and prenatal clinics. Cases were infertile males whose partner had a normal infertility evaluation and controls were fertile males whose partner had a pregnancy within 2 years. Exposures were assessed by self-report questionnaires. Bivariate, stratified, and multivariable analyses were performed. Sensitivity analysis was conducted to assess the influence of a potential unidentified confounder on the results. 650 infertile cases and 698 fertile controls were compared. In the final model, current alcohol consumption (OR=1.6, 95%CI 1.1–2.2), electric blanket use (OR=7.4, 95%CI 2.3–23.4) and waterbed use (OR=4.4, 95%CI 1.7–11.0) were associated with a greater likelihood of infertility. A protective effect on infertility was observed with video display terminals (OR=0.54, 95%CI 0.34–0.87), marijuana (OR=0.40, 95%CI 0.19–0.85), radiation (OR 0.50, 95%CI 0.26–0.97), work-related stress (OR=0.54, 95%CI 0.32–0.90), and surprisingly hot bath use (OR=0.49, 95%CI 0.28–0.85). No significant associations were noted between smoking, exercise, shift work, metal fumes, electric magnetic fields, space heaters, Jacuzzi, solvents, lead, paint, pesticides, vibration, coffee or tea and fertility. In the subgroup comparison of cases with male factor vs. unexplained infertility, alcohol consumption was 34% more likely to be related to unexplained infertility rather than male factor (OR=0.66, 95%CI 0.44–0.99) and video terminal use was 42% more likely to be associated with unexplained infertility (OR=0.58, 95%CI 0.37–0.91). Otherwise, exposures were not differentially associated with infertility type. Except for heat exposures consisting of waterbed and electric blanket use, environmental factors in men are weakly associated, if at all, with infertility in men. This study highlights many of the challenges involved in studying environmental exposures and fertility. Further large prospective studies are necessary to clarify the association between environmental exposures and infertility before widespread behavioral modification is recommended.