Incidence of proximal humerus fracture among older adults in Oslo, Norway varies by country background, marital status, and season

Sociodemographic risk factors and injury circumstances of proximal humerus fractures are insufficiently investigated. In this study, having Norwegian background and being unmarried carried the highest fracture risk. More fractures were sustained outdoors in winter versus summer. Knowledge of the injury circumstances and identifying vulnerable high-risk groups may inform preventive measures. PURPOSE: The incidence, sociodemographic risk factors, and injury circumstances of proximal humerus fractures (hereafter called humerus fractures) remain insufficiently investigated. We aimed to examine variation in humerus fracture risk by age, sex, marital status, education, and country background, and to describe injury location and seasonal distribution of humerus fractures. METHODS: In this register-based cohort study, humerus fractures sustained 2012-2022 in individuals born < 1952 living in Oslo were identified from the Norwegian Patient Registry. Information on country background, marital status, and education was obtained from Statistics Norway. Incidence rate ratios (IRRs) were estimated by Poisson regression and age-standardized incidence rates (in individuals ≥ 70 years) were calculated. RESULTS: Based on 3,520 humerus fractures (79% women) among 100,982 individuals, incidence rates were 62 (95% CI 59, 64) and 22 (95% CI 20, 24) per 10,000 person years in women and men, respectively, and increased substantially with age. Humerus fracture risk was lower in all country background categories compared to Norway (reference), with the lowest risk observed for the category mainly including individuals from Asia/Africa: IRR 0.49 (95% CI 0.38, 0.65) in women and IRR 0.37 (95% CI 0.24, 0.57) in men. An IRR of 1.17 (95% CI 1.03, 1.33) was found in unmarried compared to married women, with a corresponding IRR of 1.70 (95% CI 1.37, 2.11) in unmarried versus married men. Humerus fracture numbers peaked during winter. CONCLUSIONS: Having Norwegian background and being unmarried carried the highest humerus fracture risk. Identifying vulnerable high-risk groups is important when planning future healthcare services.