The effect of body mass index on sperm DNA fragmentation: a systematic review and meta-analysis.

Abstract

Current evidence supports the association between the high sperm DNA fragmentation (SDF) and the poor fertilization rate following either natural conception or assisted reproductive techniques (ART). On the other hand, there are conflicting results regarding the decreased sperm DNA integrity in men with high body mass index (BMI). We aimed at the present systematic review and meta-analysis at evaluating the association between BMI and SDF. We searched databases of Medline, Embase, Scopus, and Web of Science up to May 2019, to identify observational studies that assessed the associations between BMI and SDF. BMI was classified, according to the standard BMI classifications, into six categories including underweight (<18.5), normal weight (18.5-24.99), overweight (25-29.99), class I obesity (30-34.99), class II obesity (35-39.99), and class III obesity (≥40). Standardized mean differences (SMDs) and 95% confidence intervals (CIs) of SDF were calculated by using a random-effects model for BMI categories. The initial extensive literature search yielded 33,739 potentially relevant articles (3,917 from Medline, 781 from Embase, 12,685 from Scopus, and 9,348 from Web of Science). Fourteen studies (nine cross-sectional, four cohort, and one case-control studies), with a total number of 8,255 participants, were included in the meta-analysis. Finally, three studies reported higher SDF levels in obese men (BMI = 30-34.99) compared with normal-weight men (BMI < 25) (SMD: 0.23, 95% CI: 0.01, 0.46, P = 0.05, I² = 0%), but there was no difference between other categories. There is insufficient data to demonstrate a positive association between BMI and SDF. Our findings provide a rationale for conducting further cohort studies for evaluation of the association between BMI and SDF, considering potential confounders.