Atopic-eczema-associated fracture risk and oral corticosteroids: a population-based cohort study

BACKGROUND: Evidence suggests adults with atopic eczema have increased fracture risk. However, it is unclear whether oral corticosteroids explain the association. OBJECTIVE: To assess to what extent oral corticosteroids mediate the relationship between atopic eczema and fractures. METHODS: We conducted a cohort study using English primary care (Clinical Practice Research Datalink) and hospital admissions (Hospital Episode Statistics) records (1998-2016) including adults (18+) with atopic eczema matched (age, sex, and general practice) with up to five adults without atopic eczema. We used Cox regression to estimate hazard ratios (HRs) for specific major osteoporotic fractures (hip, spine, pelvis, wrist) and for any-site fracture comparing individuals with atopic eczema to those without, adjusting for six different definitions of time-updated oral corticosteroid use (ever any prescription, ever high dose, and recent, cumulative, current or peak dose). RESULTS: We identified 526,808 individuals with atopic eczema and 2,569,030 without. We saw evidence of an association between atopic eczema and major osteoporotic fractures (e.g., spine HR 1.15 99%CI 1.08–1.22; hip HR 1.11 99%CI 1.08–1.15) that remained after additionally adjusting for oral corticosteroids (e.g., cumulative corticosteroid dose: spine HR 1.09 99%CI 1.03–1.16; hip HR 1.09 99%CI 1.06–1.12). Fracture rates were higher in people with severe atopic eczema compared to people without even after adjusting for oral corticosteroids (e.g., spine HR [99%CI]: confounder adjusted 2.31 [1.91–2.81]; additionally adjusted for cumulative dose 1.71 [1.40–2.09]). CONCLUSION: Our findings suggest that little of the association between atopic eczema and major osteoporotic fractures is explained by oral corticosteroid use.