Does the Association of Comorbidity with 1-Year Mortality After Hip Fracture Differ According to Gender? The Norwegian Epidemiologic Osteoporosis Studies (NOREPOS)

Abstract

Background/objectives: Excess mortality after hip fracture is higher in men than in women. The objective was to study whether comorbidity differs in men and women with hip fracture and to what degree differences in comorbidity according to gender may explain the higher excess mortality in men.

Design: Population-based matched cohort covering the population aged 50 and older in Norway.

Setting: Specialist healthcare (individuals with hip fracture) and general population (controls).

Participants: All individuals with hip fracture aged 50 and older from 2005 to 2008 (n = 32,175) and individuals without hip fracture matched 3:1 to those with hip fracture on gender, age, and county of residence (n = 96,410).

Measurements: Comorbid diagnoses were recorded during the hospital stay. Relative and absolute excess 1-year mortality in individuals with hip fracture according to gender and Charlson Comorbidity Index (CCI) were investigated using Cox regression and linear regression, respectively.

Results: Despite lower age (mean 78.7 vs 81.7), men had higher comorbidity than women. Compared with controls, women (hazard ratio (HR) = 6.5, 95% confidence interval (CI) = 6.2-6.9) and men (HR = 7.8, 95% CI = 7.3-8.3) with a CCI of 2 or greater were more likely to die. Women with a CCI of 2 or greater had an estimated 1-year risk of dying of 44%, and controls had an 11% risk; men with a CCI of 2 or greater had an estimated risk of dying of 53%, and controls had a 12% risk. Men were twice as likely as women to die within 1 year (HR = 2.0, 95% CI = 1.9-2.1). When adjusting for comorbidity, the difference was only slightly smaller (HR = 1.8, 95% CI = 1.7-1.8).

Conclusion: Men had greater comorbidity than women, but this did not explain the difference according to gender in excess mortality after hip fracture. Men who fracture a hip are an especially vulnerable subpopulation, even when there is no apparent comorbidity, and warrant special attention in follow-up and care.

Keywords: Charlson Comorbidity Index; comorbidity; gender differences; hip fracture; mortality.