Objective: To investigate the possible association between sedentary lifestyle and testicular function, including semen quality and reproductive hormones.
Description: A large proportion of young Danish men have impaired semen quality. The causes are debated but may include lifestyle factors e.g. smoking, alcohol, obesity and diet. Recently, also television watching (TV) has been associated with poor semen quality. Besides working and sleeping, TV-viewing and other ‘screen time’ viewing is the most common activity in many Western countries and contributes many hours of sedentary behavior. In Denmark, the average time spent watching TV is 2 hours and 53 minutes per day.
To examine the hypothesis that sedentary behavior has adverse effects on the testicular function, we investigated the association of TV viewing, computer time and physical activity with markers of testicular function, including semen parameters and reproductive hormones in 1210 young men from the general Danish population.
Outcome: In this large study of young men we detected some negative associations between a sedentary lifestyle and testicular function. In particular, television watching was associated with reduced sperm counts, even when the results were controlled for differences in physical activity, diet and other lifestyle factors. Men watching television more than 5 hours/day had an adjusted sperm concentration of 37 mill/mL (95% confidence interval: 30, 44), whereas, men who did not watch television had a concentration of 52 mill/mL (95% confidence interval: 46, 62). Furthermore, an increase in follicle-stimulating hormone and decreases in testosterone and the testosterone/luteinizing hormone ratio were detected in men watching many hours of television.
It is possible that the observed association between television watching and semen quality is due to residual confounding of uncovered lifestyle factors. However, there is substantial evidence that sedentary behavior, per se, is unhealthy, but the mechanisms relating television watching and impaired spermatogenesis are unknown. The study has been published in Human Reproduction.