Obesity Is an Independent Risk Factor for Oligozoospermia, With Co-Existing Hyperglycemia Exacerbating Risks of Asthenozoospermia and Elevated Sperm DNA Fragmentation.

BACKGROUND

Metabolic health plays a critical role in maintaining male fertility and may influence offspring health. Therefore, it is necessary to incorporate metabolic indicators into the clinical assessment of male fertility. However, the relationships between different metabolic abnormalities and semen quality remain incompletely understood.

METHODS

In this retrospective cohort study, clinical data from men who underwent semen analysis and blood biochemical testing at the Fourth Affiliated Hospital of Zhejiang University School of Medicine between July 2022 and November 2025 were analyzed. Clinical characteristics, semen parameters (WHO fifth edition), and metabolic indicators were collected. Participants were classified as obese (BMI ≥ 28 kg/m2) or non-obese according to Chinese criteria. Further stratified analysis was conducted according to the presence of concomitant metabolic abnormalities (elevated fasting blood glucose or hypertension). Multivariate logistic regression and stratified analysis methods were employed to evaluate the association between obesity, its associated metabolic abnormalities, and semen quality, as well as sperm DNA fragmentation index (DFI).

RESULTS

This study included 1048 men, comprising 765 non-obese individuals and 283 obese individuals. Obese men had a significantly higher prevalence of oligozoospermia than non-obese men, whereas other semen parameters and DFI did not differ significantly. Multivariate analysis identified obesity as an independent risk factor for oligozoospermia. Among obese men, those with elevated fasting blood glucose had significantly higher rates of asthenozoospermia and high DFI compared to those with normal glucose levels. However, no statistically significant differences were observed in the distribution of oligozoospermia, asthenozoospermia, teratozoospermia, or high DFI.

CONCLUSIONS

Obesity is an independent risk factor for oligozoospermia. In obese men with elevated fasting blood glucose, sperm function impairment is further exacerbated, manifesting as asthenozoospermia and increased sperm DFI. This study highlights the cumulative adverse effects of metabolic disorders on male reproductive function.