Parental rheumatoid arthritis and long-term child morbidity: a nationwide cohort study

Objective We have reported increased long term morbidity in children of parents with rheumatoid arthritis (RA). Here we assess child mortality and case fatality in the same cohort. Methods All singletons born in Denmark from 1977 to 2008 were identified through linkage of Danish National registries. Cox proportional hazard model was used to calculate hazard ratios (HR’s) of death from all causes among children exposed to parental RA, compared to unexposed children. Risk of death after infection or respiratory diseases was also assessed for children below the age of 5 years. Results 1,917,723 new-borns were followed for an average of 16 years. Of these 13,556 were exposed to maternal RA and 6,330 to paternal RA. Overall mortality rates in children exposed to maternal or paternal RA did not differ from unexposed children: HR 0.98 [95% CI 0.84, 1.15] and 1.08 [95% CI 0.86, 1.36] and neither did the risk of death below the ages of 5 years, 3 years, or 1 year. Below the age of 5 years, 6,106 children of parents with RA were diagnosed with respiratory diseases and 3,320 with infectious diseases. Case fatalities in children with these diseases were not significantly higher than those for unexposed children: HR 1.11 [95% CI 0.74–1.66] and 0.84 [95% CI 0.52–1.35], respectively. Conclusion Children of parents with RA had similar mortality as other children, also after diagnoses of respiratory or infectious diseases.

Our results suggest that in utero exposure to maternal RA is associated with an increased risk of thyroid disease and epilepsy in childhood and adolescence, and in particular an increased risk of RA, compared to children born to mothers without RA. These important findings should encourage pediatricians and general practitioners to have an increased awareness of certain chronic diseases in children exposed to RA in utero.

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