Excess weight affects sperm production
MedWire News: Men who are overweight or obese are more likely to have a low sperm count (oligospermia) or lack sperm altogether (azoospermia) than normal-weight men, suggest findings from a French study.
The findings come from a meta-analysis conducted by Sebastian Czernichow (University of Versailles St Quentin en Yvelines, Paris) and colleagues which showed an inverse association between overweight or obesity and abnormal sperm count in a population of over 9500 men.
"The global obesity epidemic parallels a decrease in male fertility," say the researchers. "Yet the association between body mass index (BMI) and sperm parameters still remains controversial. A negative correlation between BMI and sperm concentration or total sperm count was shown by several reports but not documented by others."
To update evidence on the association between BMI and sperm count, the researchers decided to conduct a systematic review and meta-analysis of published literature reporting on the impact of BMI on sperm count. The team conducted their study in accordance with the Preferred Reporting Items for Systemic Reviews and Meta-analyses statement.
Using PubMed and EMBASE, the researchers identified a total of 31 relevant articles investigating the relationship between BMI and sperm parameters. The authors of the articles were asked to complete a standardized data form detailing sperm counts according to BMI categories.
After excluding articles due to lack of response from authors or incomplete data, a total of 14 eligible studies were included in the meta-analysis, giving a total study population of 9779 individuals.
"The strengths of our meta-analysis are a large sample size based on a collection of individual level data," comments the team.
The men were divided into categories according to whether they were underweight (BMI <18.5 kg/m2), normal weight (BMI 18.5-24.9 kg/m2), overweight (BMI 25.0-29.9 kg/m2), or obese (BMI ≥30.0 kg/m2). They were also stratified by total sperm count as having normozoospermia (≥40 x 106 spermatozoa per ejaculate), oligozoospermia (<40 x 106 but >0 spermatozoa per ejaculate), or azoospermia (absence of spermatozoa), as specified in World Health Organization guidelines.
As reported in the Archives of Internal Medicine, the overweight men were significantly more likely than normal-weight men to present with oligospermia or azoospermia, at odds ratios (ORs) of 1.11 and 1.39, respectively.
Furthermore, among obese men, the increased risk for oligospermia and azoospermia compared with that of normal-weight men was even more pronounced, at ORs of 1.42 and 1.81, respectively.
"These data strongly suggest that excess body weight affects sperm production," write Czernichow and colleagues, who conclude that "overweight and obesity are associated with an increased risk of azoospermia or oligoospermia."
By Sally Robertson