Introduction: Given the rising rates of overweight and obesity in men of reproductive age, this study was designed to examine the association between body mass index (BMI), waist circumference, and sperm parameters in male partners of subfertile couples.
Methods: The study involved 450 men who, with their female partners, were seeking reproductive treatment or specialized preconception care. The couples completed questionnaires regarding various lifestyle factors (eg, age, ethnicity, active and passive smoking, alcohol, and medication use). Sperm samples were analyzed for various sperm parameters. Overweight was defined as ≥25 and <30 kg/m2 and obesity was defined as BMI ≥30 kg/m2.
Results: Overweight and obese men had significantly lower ejaculate volume (P<0.05) and sperm count (P<0.05), and a lower percentage of progressive motility type A spermatozoa (P=0.02), which are fast straight-moving sperm. Overweight also was associated with a higher percentage of motility type C spermatozoa (P=0.002), which only move locally and are considered of poor quality.
After adjusting for lifestyle factors, being overweight was negatively associated with the percentage of progressive motility type A spermatozoa (P=0.036) and positively associated with the percentage of motility type C spermatozoa (P=0.002). Obesity was associated with low ejaculate volume (P=0.02), sperm concentration (P=0.006), total sperm count (P=0.001), and total motile sperm count (P=0.007).
Men with a waist circumference ≥102 cm had lower sperm concentration (P=0.05), total sperm count (P=0.001) and total motile sperm count (P=0.02) than men with smaller waist circumference. These associations disappeared after adjusting for BMI.
Conclusion: Men who are overweight or obese have poorer semen quality, independent of other lifestyle factors. Both the quantity of spermatozoa and their motility are impacted by body weight. BMI appeared to have a stronger impact on sperm quality than did waist circumference.
Hammiche F, Laven JS, Twigt JM, et al. Body mass index and central adiposity are associated with sperm quality in men of subfertile couples. Hum Reprod. 2012;27(8):2365-2372.
Commentary by Tamara L Wexler MD, PhD
Tamara L. Wexler, MD, PhD, is an endocrinologist specializing in reproductive and neuroendocrinology, and an Attending in Medicine, Massachusetts General Hospital, Boston, MA.
Hammiche and colleagues set out to investigate the relationship between BMI, central adiposity as measured by waist circumference (WC), and measures of sperm quality, in men seeking reproductive assistance.
The cohort consisted of male partners of couples who visited a reproductive center in Rotterdam between 2007and 2010, seeking fertility. (Eisenberg and colleagues looked at similar measurements in men without known fertility issues.) A total of 450 men were included; the authors also provided baseline data on a group of 790 non-participants who were presumably drawn from the same couples but lacked recent sperm analysis. The participating men averaged 35 years old, with a BMI of 26.3 kg/m2 and WC of 94 cm; 70% were of Dutch ethnicity, with the Dutch men having lower average BMI in sub-analysis. In general, older men had a higher BMI. BMI was correlated with WC.
Body measurements were standardized. BMI was divided into 3 categories: ≤25, 25-29.9, and ≥30 kg/m2. The 8 men who would have qualified as underweight (≤18.5 kg/m2) were excluded from the analysis. Waist circumference was dichotomized as high- or low-risk at a cutoff of 102 cm, with further analysis by quintile of WC.
Fertility measures included ejaculate volume, total sperm count, and sperm concentration [note that these are related with volume x concentration = count], and total motile sperm count, with percentages of sperm with motility types A and B further grouped as progressive motility and types C and D as immotile. (Type A sperm are more favorable for fertility; types C and D sperm are considered of poor quality.)]
Overweight and obesity were both associated significantly with lower ejaculate volume and total sperm count; there also was a trend with sperm concentration that did not reach significance. Total motile sperm count did not differ significantly between groups, but overweight was associated with a lower percentage of type A motility sperm, and obesity with a higher percentage of type C sperm. There was no significant difference in percent of type B sperm, though there was a trend towards higher percentages with higher BMI class, and no difference in type D sperm (which had a percentage of 52% - 53% in all three BMI groups.)
The high-risk WC group had significantly lower sperm concentration, ejaculate volume, and sperm count. Looking across quintiles, the association with sperm parameters was seen in the highest quintile of WC (>104 cm). No association with motility measurements was seen after adjusting for potential confounders. The correlation with BMI was stronger than that with WC: after adjusting for BMI and WC residuals in multivariable regression analysis, there was no significant association seen between WC and sperm concentration, sperm count, and ejaculate volume.
The authors concluded that both BMI and WC are associated with sperm quality in male partners of subfertile couples seeking fertility (particularly ejaculate volume, sperm concentration, and sperm motility). The authors used not only BMI—as many previous studies have done—but also WC to measure central adiposity; they found an association between WC and sperm parameters in the highest quintile (similar to the high-risk dichotomized group), but that the association might reflect the stronger correlation with BMI.
The BMI results in this study differ somewhat from those of Chavarro and colleagues in that the Chavarro study, while showing a significant and inverse relationship between BMI and ejaculate volume, did not see the association with sperm concentration (an association that was seen in a number of earlier studies). However, the Chavarro study did look at a population with different levels of obesity, which were subcategorized. In interpreting the results, it is important to note that the cohort consisted of male partners in couples seeking help with fertility (classified by the authors as subfertile couples), and with a relatively lower percentage of obese men (16%, vs 26% in the Chavarro cohort).
In summary, high BMI was associated with lower ejaculate volume and sperm count, and a poorer sperm motility profile. The highest WC group had lower ejaculate volume and sperm count and concentration, but the statistical significance of the association was not maintained after adjusting for BMI and WC residuals in multivariable regression analysis.