Male patients with inflammatory joint diseases are less likely than controls to be childless: results from a Norwegian population-based cohort study of 10 865 patients

Objectives To investigate the number of children per man and the proportion of childless men as a proxy of fertility in a national cohort of men with inflammatory joint diseases (IJDs), compared with matched controls from the general population. Methods This is a nationwide, population-based retrospective cohort study. Male patients with IJDs (n = 10 865) in the Norwegian Arthritis Registry were individually matched 1:5 on birth year and county of residence with men without IJDs obtained from the National Population Register (n = 54 325). Birth data were obtained from the Medical Birth Registry of Norway. We compared the mean number of children per man and the proportion of childless men and analysed the impact of age and year of diagnosis. Results The mean number of children per man in the patient group was 1.80 versus 1.69 in the comparison group (p <0.001), and 21% of the patients in the patient group were childless versus 27% in the comparison group (p <0.001). The finding of less childlessness and higher number of children per man remained consistent across age at diagnosis, except for those diagnosed at age 0-19 years. The difference in childlessness was most pronounced for men diagnosed after year 2000, especially when diagnosed at 30-39 years of age (22% vs 32%, p<0.001). Conclusion In this large cohort study we found that patients with IJD have a higher number of children and are less likely to be childless compared with controls. Factors associated with developing or having an IJD might influence fertility and this requires further investigation.