Men with inflammatory joint disease, similar to rheumatoid arthritis, are less prone to be childless and have more children than their healthy peers, suggests research published online within the Annals of the Rheumatic Diseases.

As yet unknown aspects related to developing the disease and/or its treatment might influence fertility, suggest the researchers.

Autoimmune diseases are on the rise within the West, and impaired fertility has been reported in Norwegian women with inflammatory joint diseases. But only just a few studies the potential impact on men’s fertility have been carried out, explain the researchers.

To explore these issues further, using childlessness and number of kids as proxies for fertility, the researchers drew on a national group of 10,865 Norwegian men with either rheumatoid arthritis (37%), psoriatic arthritis (33%), or spondyloarthritis (30%). Each of them was matched with 5 healthy men (54,325) from the overall population.

Between 1967 and August 2021, 111, 246 children were born to the whole variety of 65,190 men. Average age of first time fatherhood was 27 amongst the boys with inflammatory joint disease and 28 within the comparison group. The typical age at diagnosis was 44.

Births and childlessness were divided into 3 time periods, reflecting major changes in drug treatment for inflammatory joint diseases:1967-85 (before the appearance of methotrexate; 575); 1986–99 (methotrexate;1360); and 2000–21 (use of biologics; 8930).

The typical number of kids each patient fathered was 1.8 compared with 1.7 within the comparison group, and around 1 in 5 (21%) of the patients was childless compared with greater than 1 in 4 (27%) within the comparison group.

The number of kids born to men in each groups was as follows: one child, 15% vs 14%; two, 36% vs 33%; three, 20% vs 19%; and 4 or more, 7% vs 7%.

The difference in childlessness and number of kids between the 2 groups was seen in all age brackets, apart from those aged 19 and younger. Similarly, the proportion of childless men remained significantly lower among the many patients than within the comparison group for those diagnosed between the ages of 20 and 79.

These differences were consistent over time, but the biggest difference in number of kids was numerically highest for those diagnosed after 2000: average of 1.8 vs 1.6. These patients also had the bottom risk of childlessness: 22% vs 28%.

Within the 2000–21 era, the biggest absolute difference in childlessness was observed amongst men diagnosed of their 30s: 22% vs 32%. Within the 1967–85 and 1986–99 eras, the differences were less obvious.

That is an observational study, and as such, no firm conclusions might be drawn about cause. And except for the disease itself, psychological and socioeconomic aspects, employment status and smoking could all influence fertility-;aspects that the researchers were unable to guage.

But they conclude: “Male patients with [inflammatory joint disease] could also be reassured that no impairment of fertility is predicted. Nonetheless, substudies in accordance with specific diagnoses must be performed to supply more targeted patient information.“

They usually add: “Our finding of less childlessness and the next number of kids per man in patients with [inflammatory joint disease] is novel and generates latest hypotheses regarding associations between fertility, inflammatory rheumatic diseases and immune-modulating drugs. This should be investigated further.“