Is there an increased risk of hip fracture in multiple sclerosis? Analysis of the Nationwide Inpatient Sample

BACKGROUND: Impaired ambulation, frequent falls, and prolonged immobilization combined with the high rate of vitamin D deficiency in people with multiple sclerosis (MS) could lead to an increased risk of hip fracture. METHODS: A retrospective cohort analysis of 20 years of the Nationwide Inpatient Sample (AHRQ.gov), a 20% stratified yearly sample of USA hospital admissions from the year 1988–2007, was performed. Based on International Classification of Diseases Ninth Revision (ICD9) codes, admissions with a primary diagnosis of acute hip fracture (ICD9 code 226.xx) and a secondary diagnosis of MS (ICD9 code 340) was identified. Indirect adjustment was used to compare the prevalence of MS in this population with that of the USA. Significance was set a priori at P<0.0001 due to the large number of records and multiple comparisons. RESULTS: A total of 1,066,404 hip fracture admissions were identified and 0.25% had MS. Those with MS were younger, had lower mortality rates (0.25% for people with MS versus 2.97% for those without MS, P<0.0001) and lower rates of discharge to nursing home or rehabilitation (69.25% for people with MS versus 72.17% for those without MS, P<0.0001). When compared with the population prevalence, the predicted prevalence of MS among patients with hip fracture was 2.844 (95% confidence interval [CI] 2.837–2.852) greater than expected when adjusted for age, 2.505 (95% CI 2.499–2.512) when adjusted for sex and age, and 2.175 (95% CI 2.168–2.182) when adjusted for race (white, black). Race was specified for only 65% of the sample. CONCLUSION: In this nationwide sample of 20 years of hospital admissions in the USA, the prevalence of MS in the population with hip fracture was greater than twice that predicted, and MS patients suffered an acute fracture at an earlier age.