High body mass index has a deleterious effect on semen parameters except morphology: results from a large cohort study

Objective: To evaluate the influence of body mass index (BMI) on semen characteristics. Design: Cohort study. Setting: Single private andrology laboratory. Patient(s): All patients (n = 10,665) consulting for a semen analysis from October 9, 2010, to October 8, 2011. When analyses were repeated on the same patient, only the first was included. Intervention(s): Recording of self-reported weight and height and of semen analysis. Main Outcome Measure(s): All parameters of standard semen analysis: pH, volume, sperm concentration per mL, total sperm count per ejaculate, motility (%) within 1 hour after ejaculation (overall and progressive), viability (%), and normal sperm morphology (%). Parametric and nonparametric statistical methods were applied, and results are given either with mean +/- SD, or 10th, 50th, and 90th percentiles. Result(s): Semen volume decreased from 3.3 +/- 1.6 to 2.7 +/- 1.6 mL when BMI increased from normal (20-25 kg/m(2)) to extreme obesity (>40 kg/m(2)). The same was true for semen concentration (56.4 +/- 54.9 to 39.4 +/- 51.0 million/mL), total sperm count (171 +/- 170 to 92 +/- 95 million), and progressive motility (36.9 +/- 16.8% to 34.7 +/- 17.1%). The percentage of cases with azoospermia and cryptozoospermia increased from 1.9% to 9.1% and from 4.7% to 15.2%, respectively. The other semen characteristics were not affected. Multivariate models including age and abstinence duration confirmed these results. Conclusion(s): In this study, on a large patient sample size, increased BMI was associated with decreased semen quality, affecting volume, concentration, and motility. The percentage of normal forms was not decreased. (C) 2014 by American Society for Reproductive Medicine.