The risk of hip fracture in individuals with type 2 diabetes (T2D) can be overestimated if death is not accounted for as a competing event, according to a new study in the Journal of Bone and Mineral Research.
Previous research concluded that patients with T2D have a 40% excess risk of hip fracture compared with those without the disease, and diabetes is associated with a known reduction in life expectancy. In this population-based cohort study, researchers looked at the effect of mortality as a competing risk between T2D and hip fracture rates.
The cohort included 55,891 patients with T2D and 103,093 matched controls who were observed for a median of 6.4 years and 8.0 years, respectively.
During the study period, 31.8% of patients with T2D and 23.1% of the control group died, which extrapolated to mortality rates of 48.8 (95% CI, 48.1-49.5) and 33.8 (95% CI, 33.3-34.2) per 1000 person-years, respectively. Also, 3.9% of patients with T2D and 3.3% of controls sustained a hip fracture during this time, reflecting estimated incidence rates of 6.0 (95% CI, 5.76-6.27) and 4.9 (95% CI, 4.71-5.04) per 1000 person-years, respectively.
After taking into account death as a competing event, the association between T2D and hip fracture hazard remained statistically significant (matched –unadjusted- subhazard ratio 1.17; 95% CI, 1.11-1.23). Using Kaplan-Meier functions of hip fracture probability according to T2D status, the 5-year cumulative incidence of hip fracture was 2.6% in patients with T2D and 2.1% in the control group.
With competing risk methodology, the incidence was 2.3% among patients with T2D, which was only slightly poorer than 1.9% for the controls.
“All fracture risk estimation/s on T2D patients should therefore be addressed accounting for death as a competing risk,” concluded the authors, adding that their data do, however, confirm that T2D confers a higher risk of hip fracture even after accounting for competing risk factors.
Tebé C, Martinez-Laguna D, Moreno V, et al. Differential mortality and the excess rates of hip fracture associated with type 2 diabetes: accounting for competing risks in fracture prediction matters [published online April 6, 2018]. J Bone Miner Res. doi: 10.1002/jbmr.3435