The impact of sedentary work on sperm nuclear DNA integrity

Contemporary professional jobs that often enforce a sedentary lifestyle and are frequently associated with testicular overheat, deserve special attention with respect to male fertility potential. Interestingly, the harmful effect of testicular heat stress on sperm characteristics including nuclear DNA integrity was well characterized; however, the influence of sedentary work on sperm chromatin has not yet been documented. Therefore, our research was designed to examine the potential effects of sedentary work not only on conventional semen features but also on sperm nuclear DNA status.

The study was carried out on ejaculated sperm cells obtained from men who spent ≥ 50% of their time at work (≥ 17.5 h per week) in a sedentary position (n = 152) and from men who spent < 50% of their time at work in a sedentary position (n = 102). Standard semen characteristics were assessed according to the WHO 2010 recommendations, while sperm nuclear DNA fragmentation (SDF) was evaluated using the Halosperm test.

There were no significant differences in the standard semen parameters between the study groups. The groups differed only in SDF parameter. The men who spent at least 50% of their work time in a sedentary position had a higher proportion of SDF than the men who spent < 50% of their time at work in a sedentary position (median value 21.00% vs. 16.50%, respectively). The incidence of low SDF levels (related to 0-15% sperm cells with abnormal DNA dispersion) was significantly lower (27.63% vs. 45.10%), the percentage of men with high SDF levels (related to > 30%) was significantly higher (30.92% vs. 16.67%) in group of men who spent at least 50% of their work time in a sedentary positon. Furthermore, these men were more than twice as likely to have not a low SDF level (OR: 0.4648) and had more than twice the risk of having a high SDF level (OR: 2.2381) than the men in less sedentary occupations.

Despite lack of association between sedentary work and conventional semen characteristics our study revealed detrimental effect of seated work on sperm nuclear DNA integrity. A sedentary job doubled the risk of high levels of sperm DNA damage. The pathomechanism could be related to testicular heat stress resulting in sperm chromatin remodelling failure during spermiogenesis. Therefore, it seems reasonable to simultaneously carry out routine seminological analyses and tests assessing sperm chromatin status while diagnosing male infertility.