Socioeconomic status and its association with the risk of developing hip fractures: a region-wide ecological study.

Purpose: To determine the association between socioeconomic deprivation (SES) and hip fracture risk.

Methods: Retrospective cohort study using a population-based database (primary care records) of over 5 million people. Eligibility: all living subjects registered during the period 2009-2012 and resident in an urban area.

Measures: a validated SES composite index (proportion of unemployed, temporary workers, manual workers, low educational attainment and low educational attainment among youngsters) estimated for each area based on census data.

Outcome: incident hip fracture rates as coded in medical records using ICD-10 codes.

Statistics: zero-inflated Poisson models fitted to study the association between SES quintiles and hip fracture risk, adjusted for age, sex, obesity, smoking and alcohol consumption.

Results: Compared to the most deprived, wealthy areas had a higher hip fracture incidence (age- and sex-adjusted incidence 38.57 (37.14-40.00) compared to 34.33 (32.90-35.76) per 10,000 person-years). Similarly, most deprived areas had a crude and age- and sex-adjusted lower risk of hip fracture, RR of 0.71 (0.65-0.78) and RR of 0.90 (0.85-0.95), respectively, compared to wealthiest areas. The association was attenuated and no longer significant after adjustment for obesity: RR 0.96 (0.90-1.01). Further adjustment for smoking and high alcohol consumption did not make a difference.

Conclusion: Wealthiest areas have an almost 30% increased risk of hip fracture compared to the most deprived. Differences in age-sex composition and a higher prevalence of obesity in deprived areas could explain this higher risk.