Adults with polio are at risk of hip fracture from middle age: A nationwide population-based cohort study

Background: Having motor impairment since childhood and being at risk of osteoporosis and falls, adults with polio would be more likely to suffer a hip fracture (HF) and may experience different epidemiological characteristics from the general population. Objective: To estimate the risk and incidence of HF in adults with polio. Design: Using a national database, we conducted a population-based cohort study. We identified patients with polio using the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) code of 138. For each patient with polio, we randomly selected five age- and sex-matched control subjects. Those subjects aged <40 years were excluded. We analyzed participants aged 40˜64 years (middle-aged) and subjects aged ≥65 years (elderly) separately and recognized subjects who had an HF (ICD-9-CM code, 820) only when they received hospitalization to care for the illness from January 1, 2003 to December 31, 2008. Results: We identified 403 adults with polio (mean age ± standard deviation, 47.2 ± 8.6 years). Compared to the controls, patients with polio had a higher incidence of HF (all, 4.1 vs. 1.1/1000 person-years, p = 0.002; middle-aged, 2.3 vs. 0.3/1000 person-years, p < 0.001; male, 6.2 vs. 0.9/1000 person-years, p < 0.001); had a younger mean age (±standard deviation) of fracturing a hip (61.0±14.9 vs. 74.4±9.3 years, p = 0.015); had a lower cumulative HF-free probability (±standard error) before the age of 65 years (0.970±0.017 vs. 0.988±0.007, p<0.001) and throughout the study duration (0.415 ± 0.296 vs. 0.682 ± 0.158, p<0.001); and had a higher risk of HF, yielding an adjusted hazard ratio (95% confidence interval) of 3.58 (1.45˜8.79, p = 0.006). Patients with polio aged >48.2 years were likely to experience an HF. Conclusions: Adults with polio are at risk of HF. A customized HF prevention program is important for people with polio. The program should be started early in middle-age and should include men.