Hip fracture incidence and mortality in chronic kidney disease: the GLOMMS-II record linkage cohort study

Abstract

Background: Individuals on renal replacement therapy (RRT) have increased fracture risk, but risk in less advanced chronic kidney disease (CKD) is unclear.

Objective: To investigate CKD associations with hip fracture incidence and mortality.

Design: Record linkage cohort study Grampian Laboratory Outcomes Mortality and Morbidity Study II.

Setting: Single health region in Scotland.

Participants: All individuals (≥15 years) with sustained CKD stages 3-5 and those on RRT, and a 20% random sample of those with normal renal function, in the resident population in 2003.

Outcome measures: Outcomes were (1) incident hip fracture measured with (A) admissions or (B) deaths, with at least 5.5 years follow-up and (2) post-hip fracture mortality. Unadjusted and adjusted, incident rate ratios (IRRs) and mortality rate ratios were calculated using Poisson regression.

Results: Of 39 630 individuals identified in 2003 (41% males, mean age 63.3 years), 19 537 had CKD stages 3-5, 345 were on RRT and 19 748 had normal estimated glomerular filtration rate (eGFR). Hip fracture incidence, measured by admissions, was increased in CKD stages 3-5 (compared with normal eGFR), both overall (adjusted IRR 1.49 (95% CI 1.24 to 1.79)) and for individual CKD stages 3a, 3b and 4. Hip fracture incidence, measured using deaths, was increased in those with CKD stages 3b and 4. Post-hip fracture mortality was only increased in CKD stage 4. There was only a small number of individuals and events for CKD stage 5, resulting in insufficient statistical power.

Conclusion: Hip fracture incidence was higher in CKD stages 3-5 compared with normal eGFR. Post-hip fracture mortality was only increased in CKD stage 4. Reducing hip fracture incidence in CKD through regular fall and fracture risk review should reduce overall deaths after hip fracture in the population.

Keywords: chronic kidney disease; cohort; death; hip fracture; incidence; mortality.

Figure 1

Entry to the study, follow-up time and censoring for (i) hip fracture incidence and (ii) post-hip fracture mortality. The index date was defined as the first abnormal eGFR (<60 mL/min/1.73 m²) from a creatinine measured between 1 January and 31 December 2003. Where all eGFR values in 2003 were normal, the last value and date were taken as the index. Primary outcome, hip fracture incidence measured using (A) hip fracture admission (from hospital admissions data, where hip fracture was recorded as the main or additional diagnosis (ICD-10 code S72)) and (B) hip fracture-related death (from national death records, where hip fracture was recorded as a main or other cause of death). Secondary outcome, post-hip fracture mortality in individuals who had a hip fracture admission, both (A) all-cause mortality (ACM) and (B) specifically hip fracture-related mortality (HFM) where hip fracture was recorded as main or other cause of death. eGFR, estimated glomerular filtration rate; ICD-10, International Classification of Diseases, 10th Revision.

Figure 2

Flow diagram of study population from GLOMMS-II. CKD, chronic kidney disease; eGFR, estimated glomerular filtration rate; GLOMMS-II, Grampian Laboratory Outcomes Morbidity and Mortality Study II; RRT, renal replacement therapy (dialysis and transplants).