Somers EC et al. – The authors quantified the familial risk of systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) in a nationwide cohort study. For both diseases, transmission was comparable among both female and male offspring of maternal and paternal cases. These data provide evidence at the population level that X–chromosomal factors do not play a major role in sex disparities associated with the risk of SLE and RA.Methods
- A population–based cohort of parent–offspring triads from Denmark (1977–2010) was established. SLE and RA incidence rates among offspring were calculated, and Cox regression was performed to assess the sex–specific risk of disease in offspring according to maternal or paternal disease history.
- Among 3 513 817 parent–offspring triads, there were 1258 SLE cases among offspring (1095 female, 163 male) and 9118 cases of RA/JRA (6086 female, 3032 male).
- Among female offspring, SLE risk was nearly the same according to maternal (HR 14.1) or paternal (HR 14.5) history (p=NS); likewise among male offspring, risk according to maternal (HR 5.5) and paternal (no cases) history were similar (p=NS).
- For RA, all risk estimates were similar, regardless of the sex of the offspring or parent (HR 2.6–2.9; p=NS).