Spermienparameter und Reproduktionsbiographie als interagierende Prädiktoren männlicher Lebensspanne: Eine medizinsoziologisch-andrologische Studie an 2294 Patienten der Kinderwunschsprechstunde der Marburger Universitätshautklinik 1949-1994

The aim of the current study is to analyse the association between fertility and lifetime mortality in men under consideration of their individual reproductive history data and on the basis of previous investigations (e.g. Groos et al. 2006, Seydel 2010) providing evidence that poor sperm count can predict higher mortality. This can be understood as a direct effect. Spermatogenesis is a marker for the vital status of an organism. This can also be considered an indirect effect. Men with poor sperm count become less frequently fathers and therefore show higher mortality. To investigate both the direct and the indirect effect the current study distinguishes between sperm status and paternity. The study is based on patients' spermiograms born between 1892 and 1941 who have attended the andrological service at the Hospital of the Philipps University Marburg between 1949 and 1994 resulting in a sample size of 2294 cases. Data of the vital status were gathered through the assistance of the public registration offices. By the end of December 2010 the vital status had been identified for 1417 former patients. Additionally, a survey was carried out in order to collect data on the reproductive history which was only available in parts or missing in the medical records of the andrological service. For already deceased patients a proxy-interview with the spouses was conducted. Comprehensive information on the number of biological children (hence biological fatherhood) could be obtained for 631 cases. To determine the fertility, patients were classified into two groups depending on their sperm count. According to the criteria (reference values) established in WHO (2010) fertile (≥15×10⁶/ml) and subfertile (<15×10⁶/ml) men were distinguished. Sperm concentration and overall fertility were included in the analysis as continous variables in order to investigate the association between fertility and mortality. The results of semi-parametrical and parametrical tests across the entire study population, namely all cases with known vital status until December 31, 2010 and available information on sperm concentration (n=1417), revealed a higher mortality risk for subfertile men compared to fertile men under consideration of the survival time since the date of birth and the date of examination. The results on the extended Mortality Follow-Up until the 31st of December 2010 did not only replicate those found in previous studies by Groos et al. (2006) and Seydel (2010) for the early birth cohorts but also for all age groups and under inclusion Zusammenfassung/Summary 156 of azoospermic men and the survival time since examination in the analysis. However, contrary to Seydel's study (2010) no association between the overall fertility and the survival time since birth and examination was found. Furthermore, in consideration of fecundity as possible co-variate no relation was found between fertility and mortality depending on survival time since birth or examination within the population of the survey (n=631). Difference in mortality depending on fertility status and sperm concentration between childless men and fathers were only found in a stratification analysis of the fecundity status and under consideration of survival time since examination in application of full parametric tests. A group-wise comparison of childless men and fathers with comparable overall fertility and sperm concentration revealed a higher mortality risk for childless men. No elevated mortality risk was determined for subfertile childless men in comparison to subfertile fathers. A significant interaction was found between sperm concentration and fecundity or alternatively between overall fertility and fecundity on mortality. However, results were only significant when interaction effects were included into the model without the corresponding main effects. The present study presents evidence for an indirect (protective) effect of fecundity on mortality only in combination with good sperm properties. More specifically, childless men with poor sperm properties did not show higher mortality because of their childlessness. The results contradict previous findings of a study by Jensen et al. (2009), the only existing study differentiating between fertility and parity. The authors found a direct relationship between mortality and sperm concentration in that mortality decreases amongst men with and without children with increasing sperm concentration as well as increasing percentages of morphologically normal and motile spermatozoa. Thereby, the results of Jensen et al.'s study (2009) indicate a direct relationship between semen quality and mortality so that good semen quality was considered a biomarker of overall health of men. Since the present study is based on a relatively small sample it would be desirable to replicate the results on the basis of a larger dataset in order to verify the results' generalisability.