Incidence, timing and impact of comorbidity on second hip fracture: a population-based study

Background: To quantify the incidence and timing of second hip fracture, and to evaluate the relative impact of comorbidities on risk of second hip fracture. Methods: Hospitalization records for individuals aged 65, admitted to a New South Wales hospital for fall-related hip fracture between 1 January 2005 and 31 December 2009 were linked. Comorbidities were identified from the records using a 1-year look-back period. To calculate second hip fracture rates, individuals were followed until death, fracture or end of study period (31 December 2012). Time-dependent competing-risk hazards regression was used to assess the relative contribution of each comorbidity to fracture risk, adjusting for age and sex. Results: Of the 24 500 individuals who sustained at least one hip fracture, 2.9% experienced a second within a year, 6.1% within 3 years and 9.4% within 8 years. Malnutrition/cachexia (hazard ratio (HR): 2.47; 99.9% confidence interval (CI): 1.87-3.26), dementia (HR: 2.15; 99.9% CI: 1.80-2.57), congestive heart failure (HR: 1.62; 99.9% CI: 1.30-2.04), Parkinson's disease (HR: 1.51; 99.9% CI: 1.08-2.10), cerebrovascular disease (HR: 1.41; 99.9% CI: 1.06-1.89) and osteoporosis (HR: 1.36; 99.9% CI: 1.11-1.67) were associated with increased risk of second hip fracture within 3 years. Mortality was high; with 26% of individuals dying within a year, 44.9% within 3 years and 70.2% within 8 years. Conclusions: One in 11 older individuals with an initial hip fracture sustained a second hip fracture. While the priority is to prevent the first hip fracture, those that have sustained a hip fracture should be seen as a high risk population and be targeted for future falls and fracture prevention strategies.