Risk for Fractures with Centrally Acting Muscle Relaxants: An Analysis of a National Medicare Advantage Claims Database

BACKGROUND: In older adults, both muscle relaxants and benzodiazepines are associated with sedation and cognitive impairment. Although benzodiazepines have been linked to falls and fracture injuries, no studies have examined the risk of fracture associated with muscle relaxants. OBJECTIVE: To determine whether muscle relaxants identified in the Beers criteria are associated with an increased risk of fracture injuries and to compare this risk to that with benzodiazepine use. METHODS: We conducted a case-control study using both medical and pharmacy claims data from 1.5 million enrollees in the Medicare Advantage plans of a large health maintenance organization. We matched 8164 cases of fractures with 8164 controls based on age, sex, health plan, and comorbidities. We measured the use of muscle relaxants, short-acting benzodiazepines, and long-acting benzodiazepines. Adjusted odds ratios were estimated using conditional logistic regression. RESULTS: After adjusting demographic and clinical covariates, muscle relaxants, long-acting benzodiazepines, and short-acting benzodiazepines were associated with a high risk of fracture injuries, with odds ratios of 1.40 (95% Cl 1.15 to 1.72; p<0.001), 1.9(95% Cl 1.49 to 2.43; p<0.001), and 1.33(95% Cl 1.15 to 1.55; p <0.001), respectively. CONCLUSIONS: An elevated risk of fracture injuries was noted among older adults using muscle relaxants. Our findings provide evidence of an association between the risk of fractures and the use of centrally acting muscle relaxants in older adults. This association supports current recommendations advising extreme caution in prescribing muscle relaxants to older adults.