Study question: Is parental age at delivery associated with a man's semen quality?
Summary answer: In this large register-based study both mother's and father's age are found to have minimal effects on semen quality in men.
What is known already: Both maternal and paternal age have been associated with a range of adverse health effects in the offspring. Given the varied health effects of parental age upon offspring, and the sensitivity of genital development to external factors, it is plausible that the age of a man's mother and father at conception may impact his reproductive health. To our knowledge this is the first examination of the effects of parental age on semen quality.
Study design, size, duration: A retrospective cohort study of 10 965 men with semen data and parental data.
Participants/materials, setting, methods: The study was based on Danish men referred to the Copenhagen Sperm Analysis Laboratory due to infertility in their partnership. Men born from 1960 and delivering a semen sample until year 2000 were included. The men were linked to the Danish Civil Registration System to obtain information on parent's age at delivery. Logistic regression analyses were used to calculate odds ratios and 95% confidence intervals for impaired semen quality. Linear regression analyses were used to examine a relationship between semen parameters and paternal age.
Main results and the role of chance: There were no convincing effect of either mother's or father's age on a man's semen quality. As no trends were noted, the few statistically significant results are likely attributable to chance.
Limitations, reasons for caution: Information regarding individual subject characteristics which may impact sperm production (i.e. smoking, BMI) were not available. While our sample size was large, we cannot exclude the possibility that a trend may have been identified with a still larger sample. In addition, the Danish Civil Registration System is merely administrative and hence does not discriminate between biological and adopted children. However, the low rate of adoption (≈2%) suggests that misclassification would have a minimal impact. The men were all referred to the laboratory for infertility problems in their partnership and, therefore, do not represent the general population. We, however, compared semen quality among men within the cohort, and it is therefore less important whether they, in fact, represent the general population.
Wider implications of the findings: The current study found no link between parental age and a son's semen quality, suggesting other factors may explain recent impairments in men's reproductive health.
Study funding/competing interest(s): This work was supported by the Hans and Nora Buchard's Fund and the Kirsten and Freddy Johansen's Fund. No competing interests.
Trial registration number: Not relevant.
Keywords: fertility; parental age; reproduction; semen.