Background: Overweight and obese men have been reported to have lower sperm counts and hormonal changes, but data are lacking regarding effects on couple fertility.
Methods: We examined the relationship between male body mass index (BMI) and infertility in couples enrolled in the Agricultural Health Study in the United States. The analysis sample was limited to couples (wife <40 years old) with an attempt at pregnancy in the last 4 years based on pregnancy and fertility data provided by wives. Infertility was defined as not conceiving a pregnancy after at least 12 months of unprotected intercourse regardless of whether or not a pregnancy ultimately occurred. Self-reported weight and height were used to calculate BMI (kg/m2). Adjusted odds ratios (aORs) for infertility associated with increases in male BMI were calculated with logistic regression.
Results: Adjusting for potential confounders, a 3-unit increase in male BMI was associated with infertility (aOR = 1.12; 95% confidence interval = 1.01-1.25; n = 1329). There was a dose-response relationship, and the BMI effect was stronger when the data were limited to couples with the highest-quality infertility data. The association between BMI and infertility was similar for older and younger men, suggesting that erectile dysfunction in older men does not explain the association.
Conclusions: This report of lower fertility in overweight and obese men needs replication. If the findings are robust, programs to prevent obesity may improve men's reproductive health and save medical costs for infertility treatment.