Physical activity, sedentary time and sperm DNA fragmentation index in healthy Japanese men

Are physical activity and sedentary time associated with the DNA fragmentation index (DFI) score and conventional semen parameters in healthy Japanese men?

Baseline data from the Preconception Research and Education Study for Men, an ongoing randomized controlled trial, were used to assess the long-term effects of preconception health education on male fertility. This cross-sectional analysis included 323 men, aged 20-39 years, recruited from September 2021 to December 2022 at workplace health check-up sites in Japan. Demographic, lifestyle and health check-up data were collected, and physical activity and sedentary time were measured using the International Physical Activity Questionnaire-Short Form. Semen quality was assessed using the DFI score and conventional semen analyses. Generalized linear models were used to evaluate the associations between physical activity, sedentary time and semen parameters, adjusting for confounders.

Higher total physical activity was associated with a lower DFI score (P-value for trend = 0.002), with the third and fourth total physical activity quartiles showing a 21% (95% CI 5-34%, P = 0.013) and a 29% (95% CI 12-43%, P = 0.002) reduction in DFI score compared with the first quartile reference, respectively. There was a trend for a shorter sedentary time to be associated with a lower DFI score, but this failed to reach significance (P-value for trend = 0.057). The first sedentary time quartile showed a 22% reduction in DFI score compared with the fourth quartile reference (95% CI 3-37%, P = 0.024). There were no significant associations between total physical activity, sedentary time and conventional semen parameters.

Higher physical activity and shorter sedentary time are associated with a lower DFI score in Japanese men. However, these associations were not observed with conventional semen parameters.