Association of exposure to residential greenness with semen quality: A retrospective longitudinal study of sperm donation volunteers in Guangdong province, China

Abstract

Background: Exposure to residential greenness has been associated with benefits on certain reproductive health outcomes. However, its potential benefits on semen quality remain unknown.

Objectives: To quantitatively explore the association between exposure to residential greenness and semen quality.

Methods: We investigated 9142 sperm donation volunteers who underwent 38,682 semen examinations at Guangdong provincial human sperm bank in China during 2016-2019. Exposure to residential greenness was assessed using mean daily Normalized Difference Vegetation Index (NDVI) at each subject's residential address with a 400 m buffer during 0-90 days before each semen collection. Multivariate linear mixed models and linear regression models were used to assess the association between exposure to residential greenness and semen quality.

Results: An interquartile range increase in exposure to residential greenness was significantly associated with a 0.034 (95% confidence interval [CI]: 0.005, 0.063) ml, 4.06 (95% CI: 0.76, 7.37) × 10⁶, and 0.32% (95% CI: 0.22%, 0.41%) increase in semen volume, total sperm number, and normal forms, respectively; similar trends were observed across quartiles of exposure to residential greenness (all p-values for liner trend <0.05 except for semen volume). The association of greenness exposure with semen volume and total sperm number was stronger in subjects 18-25 years, while the association with normal forms was stronger in subjects 26 years or older. The association for sperm concentration, total sperm number, and normal forms were stronger in cool season, while the association for semen volume was stronger in warm season.

Conclusion: We found that exposure to residential greenness was significantly associated with higher semen quality. Further studies are warranted to determine the causality of the association and its underlying mechanisms.

Keywords: Exposure-response association; Male reproduction; Residential greenness; Semen quality; Sperm donation volunteer.