Abstract
BACKGROUND: Chronic inflammatory diseases (CIDs) may share aetiological factors across diseases. We used registry data to evaluate the risk of developing five common childhood CIDs dependent on the parents' disease status. METHODS: We performed a national population-based registry study by linking data from the national Danish health registers from January 1973 to March 2016 to evaluate any potential associations between parents' disease and development of CIDs among the offspring. Results were adjusted for parental age at birth, the decade of birth, gender of the child, and type of birth. A cohort of 2,699,449 liveborn children was established for investigating the primary outcome measures: diabetes mellitus (DM), rheumatoid arthritis (RA), coeliac disease, Crohn's disease (CD), and ulcerative colitis (UC) and all diseases combined (CID). RESULTS: Children with one CID affected parent (Hazard ratio (HR), 95% confidence interval (95% CI)=1.75 (1.72-1.79, p<0.001)), one multiple CID affected parent (HR=2.23 (2.11-2.34), p<0.001), and both parents affected (HR=3.10 (2.98-3.22), p<0.001) were at higher risk than children without CID affected parents. Children with DM, RA, and COE affected parents were at increased risk of three specific diseases (DM, RA and COE), whereas children with CD and UC affected parents were at increased risk of two specific diseases (CD and UC). CONCLUSION: Children with CID affected parents were at increased risk of the same CID as their parents as well as other specific CIDs dependent on the parents' CID. Future studies should address the aetiology underlying these findings to support the development of new strategies for prevention, treatment, and cure.