Association between allopurinol use and hip fracture in older patients

Background: Allopurinol reduces oxidative stress and interacts with purinergic signalling systems important in bone metabolism and muscle function. We assessed whether allopurinol use was associated with a reduced incidence of hip fracture in older people. Methods: Analysis of prospective, routinely-collected health and social care data on patients undergoing health and social work assessment in a single geographical area over a 12 year period. Exposure to allopurinol was derived from linked community prescribing data, and hospitalisation for hip fracture and comorbid disease was derived from linked hospitalisation data. Fine and Gray modelling was used to model time to hip fracture accounting for the competing risk of death, incorporating previous use of allopurinol, cumulative exposure to allopurinol as a time dependent variable, and covariate adjustments. Results: 17,308 patients were alive at the time of first social work assessment without previous hip fracture; the mean age was 73 years. 10,171 (59%) were female, and 1155 (8%) had at least one exposure to allopurinol. 618 (3.6%) sustained a hip fracture, and 4226 (24%) died during a mean follow-up of 7.2. years. In fully-adjusted analyses, each year of allopurinol exposure conferred a hazard ratio of 1.01 (95% CI 0.99, 1.02; p = 0.37) for hip fracture and 1.00 (0.99, 1.01; p = 0.47) for death. Previous use of allopurinol conferred a hazard ratio of 0.76 (0.45, 1.26; p = 0.28) for hip fracture and 1.13 (0.99, 1.29; p = 0.07) for death. Conclusion: Greater cumulative use of allopurinol was not associated with a reduced risk of hip fracture or death in this cohort.