Background/Purpose: Multimorbidity, the coexistence of 2 or more chronic conditions, is associated with increased disability and poor functional status, and may serve as an important clinical marker for hip fracture risk. We examined the role of multimorbidity on hip fracture risk and whether this differed between women and men, or by race.

Methods: Using de-identified administrative claims data from a large commercial insurance database, we identified both women and men aged ≥50 yrs who had a hip fracture between Jan 1, 2006-Dec 31, 2016, and had at least 1 yr health plan coverage pre-fracture. Subjects without known hip fracture were matched to cases exactly on sex, age, race, year, geographic region, and insurance; they were also required to have at least 1 yr health plan coverage pre-index date. Diagnostic codes and medications were captured for the year prior to fracture/index date. Using the score from the Elixhauser Comorbidity Index (Elix Index), a set of 31 comorbidities, we categorized subjects into 3 groups (0-1, 2-3, and ≥4) and used conditional logistic regression to examine the association with hip fracture. We focused on subjects identified as White, Black or Asian, and examined women and men separately.

Results: We studied 50,136 White/5,770 Black/1,130 Asian women (median age [IQR], yrs: 79 [72, 83]/ 78 [71, 83]/ 79 [71, 83], respectively) and 22,329 White/2,419 Black/451 Asian men (median age [IQR], yrs: 77 [66, 82]/ 75 [66, 81]/ 78 [67, 83], respectively) with hip fractures and an equal number of matched controls. Compared to the referent group (Elix Index 0-1), higher Elix Index was associated with increased hip fracture risk with findings similar in women and men and across races studied (Table). In further analyses with a gradient boosting model, a higher Elix Index ranked as the top influence on hip fracture risk over the individual 31 comorbidities (date not shown). In a multivariable penalized logistic regression model, the addition of medication categories to the 31 comorbidities did not contribute additional information on hip fracture risk (data not shown).

Conclusion: Multimorbidity, as assessed using the Elix Index, is associated with an elevated risk for hip fracture, in both women and men, and across races studied. A higher number of co-existing chronic conditions is associated with an even greater risk of hip fracture. Further work is necessary on determining whether specific combinations of comorbidities have a greater impact on risk.