Background: The use of skeletal muscle relaxants (SMRs) among older adults is associated with sedation and confusion, which may lead to an increased risk of falls and injuries. SMRs continue to be used among older adults, although they are on the Beers list as drugs to avoid in the elderly.
Objective: To investigate the relationship between SMR use and subsequent risk of injury.
Methods: This was a retrospective case-control study of members aged 65 years or older enrolled in an integrated health care system. Cases were defined as patients with a documented injury resulting in either a hospitalization or an emergency department or urgent care visit from January 2009 through December 2010. Cases were matched to controls in a 1:4 ratio by age and sex. Patients had to be enrolled and alive on the date of an injury (index date). SMR exposure for all cases and controls was evaluated within 60 days prior to the index date. Conditional logistic regression adjusted for covariates was performed, with risk estimates presented as odds ratios with 95% confidence intervals.
Results: From a base population of 322,806 older adults, we identified 27,974 cases of injury and 104,303 matched controls. Among the cases, 365 (1.30%) used an SMR; among the controls, 801 (0.77%) used an SMR in the 60 days prior to the index date. After adjustment for demographic and clinical covariates, risk of injury was significantly increased for patients using an SMR compared to no use (OR 1.32, 95% CI 1.16-1.50; p < 0.001). Carisoprodol was associated with an increased risk of injury (OR 1.73, 95% CI 1.04-2.88; p = 0.036), as were methocarbamol (OR 1.42, 95% CI 1.16-1.75; p = 0.001) and cyclobenzaprine (OR 1.22, 95% CI 1.02-1.45; p = 0.029).
Conclusions: Older adults using SMRs have an increased risk of injury. These findings provide evidence to support current recommendations to avoid the use of SMRs in elderly patients.