Social inequality and fractures—secular trends in the Danish population: a case-control study

Summary: We examined links between markers of social inequality and fracture risk in the Danish population, demonstrating that high income and being married are associated with a significantly lower risk. Introduction: We explored whether the risk of hip, humerus, and wrist fracture was associated with markers of inequality using data from Danish health registries. Methods: All patients 50 years or older with a primary hip (ICD10 S720, S721, S722, and S729) humerus (ICD10 S422, S423, S424, S425, S426, and S427), or wrist (ICD10: S52) fracture were identified from 1/1/1995 to 31/12/2011. Fracture patients were matched 1:1 by age, sex, and year of fracture, to a non-fracture control. Markers of inequality were as follows: income (fifths); marital status (married, divorced, widowed, or unmarried); area of residence (remote, rural, intermediate, or urban). Conditional logistic regression was used to investigate associations between these exposures, and risk of fracture, adjusting for covariates (smoking, alcohol, and Charlson co-morbidity). Interactions were fitted between exposure and covariates where appropriate. Results: A total of 189,838 fracture patients (37,500 hip, 45,602 humerus, and 106,736 wrist) and 189,838 controls were included. Mean age was 73.9 years (hip), 67.5 years (humerus), and 65.3 years (wrist). High income (5th quintile) was significantly associated with a lower odds ratio of all three fractures, compared to average income (3rd quintile). Married subjects had a significantly decreased odds ratio across all three fractures. However, no overall secular difference was observed regarding the influence of the markers of inequality. Conclusion: In conclusion, we have demonstrated important, stable associations between social inequality, assessed using income, marital status, and area of residence, and fracture at the population level. These findings can inform approaches to healthcare, and suggest that much thought should be given to novel interventions aimed especially at those living alone, and ideally societal measures to reduce social inequality.