Why do men suffer from sarcoidosis earlier than women?

Although some men like to be the ringleader when it comes to things like sports, a disease is not something you wish to surpass the fairer sex in. Unfortunately for Swedish men, they do surpass their female compatriots when it comes to an earlier onset of sarcoidosis. In Sweden, the age at diagnosis of sarcoidosis in men is 10 years younger than in women. 

Elisabeth Arkema and colleagues from the Karolinska Institutet investigated contemporary incidence and prevalence of sarcoidosis using Swedish population-based register data. Sarcoidosis is a disease of unknown cause, in which the lungs are often involved. It is associated with increased immune system activity that causes immune cell clusters, called granulomas. Despite scientific progress since sarcoidosis was first described more than 100 years ago, much remains unknown about the condition. Variations over time, place, age, sex and other characteristics may provide important information on how and why sarcoidosis occurs.

The researchers identified adults with any sarcoidosis-coded visit from the National Patient Register and found that the highest prevalence was observed in northern less densely populated counties. The investigators hypothesise this could be caused by an exposure more common in rural areas such as pine, soil, clay or occupation (e.g. metal industry, farming). Alternatively, the observed geographical variation could be the result of the genetic composition of the individuals living in different regions in Sweden. The investigators emphasise the observed geographical variation does not support the hypothesis that tick-borne bacteria such as Borrelia burgdorferi or Rickettsia Helvetica cause sarcoidosis, because ticks are more common in the southern and coastal regions where the lowest prevalence was observed.

The average age of individuals living with sarcoidosis in Sweden in 2013 was 56 years. Age at diagnosis in men was 10 years younger than in women: median age 44.9 years versus 54.0 years, respectively. The incidence peaked in males aged 30–50 years and in females aged 50–60 years. The investigators say that the earlier onset in men could be due to an environmental factor, which is more common in men and experienced at a younger age, such as an occupational exposure. Sex also plays a role in sarcoidosis occurrence through genetics, hormones, or another as-yet unidentified factor. 

Reference:
Arkema EV, Grunewald J, Kullberg S, et al. Sarcoidosis incidence and prevalence: a nationwide register-based assessment in Sweden. Eur Respir J 2016; 48: 1690–1699