Risk Factors and Trends Associated With Mortality Among Adults With Hip Fracture in Singapore

Importance

Examining trends in mortality following hip fracture and its associated factors is important for population health surveillance and for developing preventive interventions.

Objective

To examine temporal trends in, and risk factors associated with, mortality following hip fracture over 18 years in Singapore.

Design, Setting, and Participants

This retrospective, population-based cohort study included men and women aged 50 years and older admitted to Singapore hospitals for first hip fracture identified and followed up from 2000 to 2017. Demographic information, fracture type, and Charlson Comorbidity Index (CCI) score were retrieved from nationwide claims data, and mortality data were from the National Death Registry. Data were analyzed from August 2018 to December 2019.

Main Outcomes and Measures

Adjusted hazard ratios (aHRs) and their 95% confidence intervals were estimated using Cox proportional hazards regression. Kaplan-Meier life table methods were used to calculate survival following the hip fracture on a cohort basis. The crude survival over time since fracture was compared by sex, age group, ethnicity, CCI, and fracture type. Standardized mortality ratios (SMRs) were calculated using all-cause mortality obtained from Singapore population life tables.

Results

Among 36 082 first inpatient admissions for hip fractures (mean [SD] patient age, 78.2 [10.1] years; 24 902 [69.0%] female; 30 348 [84.1%] Chinese, 2863 [7.9%] Malay, 1778 [4.9%] Indian, and 1093 [3.0%] other ethnicity), elevated rates of mortality were observed for male sex (aHR, 1.46; 95% CI, 1.41-1.52), Malay ethnicity (aHR, 1.23; 95% CI, 1.15-1.30 vs Chinese ethnicity), older age (aHR, 5.20; 95% CI, 4.27-6.34 for age ≥85 years vs 50-54 years), high CCI score (aHR, 3.62; 95% CI, 3.42-3.84 for CCI ≥6 vs CCI of 0), trochanteric fractures (aHR, 1.11; 95% CI, 1.06-1.16 vs cervical fractures), and earlier cohorts (aHR, 0.59; 95% CI, 0.56-0.62 for 2012-2017 vs 2000-2005). Absolute mortality decreased significantly over time: by 21% in 2006 to 2011 and by 40% in 2012 to 2017, compared with 2000 to 2005. On long-term follow-up, differences in survival associated with sex and ethnicity tended to diminish, whereas differences associated with older age, higher CCI score, and trochanteric fractures increased. In the first year after fracture, reductions in SMR were observed comparing the periods 2013 to 2016 with 2003 to 2007 in women (SMR, 2.05; 95% CI, 1.91-2.20 vs SMR, 2.54; 95% CI, 2.39-2.70, respectively) but not among men (SMR, 3.28; 95% CI, 3.04-3.54 vs SMR, 3.42; 95% CI, 3.18-3.68, respectively).

Conclusions and Relevance

Malay ethnicity, older age, male sex, prefracture comorbidity, and trochanteric fractures were independently associated with increased risk of death, identifying population groups that could be targeted for intervention strategies. The improvement in relative mortality for women but not men suggests the need to develop interventions that improve mortality outcomes for men.