Semen quality associated with subsequent hospitalizations - Can the effect be explained by socio-economic status and lifestyle factors?

Semen quality is suggested to be a universal biomarker for future health. Previous studies have mostly been registry based excluding the possibility to address the importance of lifestyle, fertility status, health and socio-economic status. We aimed to investigate whether the association between semen quality and subsequent risk of hospitalization could be explained by differences in occupation, education, fertility, cryptorchidism, BMI or smoking; 1423 men with first semen sample at Fertility Clinic, Frederiksberg Hospital, Denmark, from 1977 to 2010 responded to a questionnaire in 2012 about current health, lifestyle, educational level and occupation. They were followed in the Danish National Patient Registry to first-time hospitalizations using ICD-8 and ICD-10 classification. Data were analysed by Cox proportional hazard regression models to adjust for the possible confounding factors. We found a significant higher risk of being hospitalized with decreasing sperm concentrations (0-15 mill/mL: HR1.78, 95% CI:1.51-2.09; 16-50 mill/mL: HR 1.37 95% CI: 1.17-1.60; 51-100 mill/mL: HR1.25 95% CI: 1.07-1.45). Same significant association of being hospitalized with decreasing total sperm counts was seen. The dose-response increase in risk in hospitalization with decreasing sperm concentration and total sperm count remained constant after further individual adjustment for occupation, marital status, fertility, cryptorchidism, BMI or smoking. The association between semen quality and subsequent morbidity was not explained by differences in lifestyle, behavioural or fertility status. We were unable to adjust for all possible confounders simultaneously due to limited sample size, and reverse causation is a possible explanation as information about education and lifestyle was obtained after semen analysis and hospitalizations occurred and may have changed as consequence of both. Semen quality may be a universal biomarker for future health not explained by lifestyle and socio-economic status, but this needs to be addressed further in future studies.