IMPORTANCE

Concussions are an acute injury that may lead to chronic disability, while statin use might improve neurologic recovery.

OBJECTIVE

To test whether statin use is associated with an increased or decreased risk of subsequent dementia after a concussion.

DESIGN, SETTING, AND PARTICIPANTS: Large extended population-based double cohort study in Ontario, Canada, from April 1, 1993, to April 1, 2013 (enrollment), and continued until March 31, 2016 (follow-up). Dates of analysis were April 28, 2014, through March 21, 2019. Participants were older adults diagnosed as having a concussion, excluding severe cases resulting in hospitalization, individuals with a prior diagnosis of dementia or delirium, and those who died within 90 days.

EXPOSURE

Statin prescription within 90 days after a concussion.

MAIN OUTCOME AND MEASURE

Long-term incidence of dementia.

RESULTS

This study identified 28 815 patients diagnosed as having a concussion (median age, 76 years; 61.3% female), of whom 7058 (24.5%) received a statin, and 21 757 (75.5%) did not receive a statin. A total of 4727 patients subsequently developed dementia over a mean follow-up of 3.9 years, equal to an incidence of 1 case per 6 patients. Patients who received a statin had a 13% reduced risk of dementia compared with patients who did not receive a statin (relative risk, 0.87; 95% CI, 0.81-0.93; P < .001). The decreased risk of dementia associated with statin use applied to diverse patient groups, remained independent of other cardiovascular medication use, intensified over time, was distinct from the risk of subsequent depression, and was not observed in patients after an ankle sprain.

CONCLUSIONS AND RELEVANCE

In this study, older adults had a substantial long-term risk of dementia after a concussion, which was associated with a modest reduction among patients receiving a statin.