Semen quality and sedentary work position.
Level 4 - case-series / case-control
Cross-sectional observational study linking clinical semen samples to job-exposure matrix data
PubMed 14718040 · doi:10.1046/j.0105-6263.2003.00428.x
What was done
Semen samples were collected between 1981 and 1983 from 3,119 men undergoing infertility evaluation across four Danish fertility centres. A total of 2,517 men returned questionnaires detailing lifestyle, leisure activities, and occupational history. The primary analysis included 1,747 men aged 18–39 years working more than 30 hours per week. Exposure to sedentary work was estimated at the job-title level using average sedentary proportions derived from the 1990 Danish Work Environment Cohort Study (DWECS) job matrix, and semen parameters were compared across quintiles of sedentary exposure.
What was found
Mean sperm concentration was 30.6 million/mL in the lowest quintile of job-specific sedentary work compared to 40.5 million/mL in the highest quintile; this difference was not statistically significant. Stratification by duration of infertility, educational attainment, fertility clinic, and spouse fertility-related disease did not alter the findings. No adverse effect of sedentary work on semen characteristics was detected.
Why it matters
Although elevated scrotal temperature can impair spermatogenesis in laboratory settings, this study indicates that occupational sitting time in daily life does not appear to be a major clinical risk factor for reduced sperm concentration.
Limits
The study was conducted entirely within a fertility clinic population rather than the general population, which may introduce selection bias. Sedentary time was not measured directly on individuals but estimated at the job-title level from a separate cohort surveyed several years later (1990 vs. 1981–1983), presenting a substantial risk of exposure misclassification. Specific numerical data for motility and morphology were not provided in the abstract.
Cited by
- contradicts Studies show an inverse relationship between time spent sitting (such as driving on a hot car seat) and sperm count and viability.