Association Between Statin Use and Risk of Dementia After a Concussion

Abstract

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.

Figure 1.. Risk of Subsequent Dementia

Cumulative incidence plots of absolute risk of dementia after injury. The x-axis shows time after injury, spanning 5 years. The y-axis shows cumulative incidence of dementia. Numerical counts indicate the number of patients alive without dementia at the corresponding time. Results show increasing incidence of dementia with time, particularly after a concussion, with reduction in risk associated with statin use. The patients with ankle sprain show minimal healthy-user bias.

Figure 2.. Risk of Subsequent Depression

Cumulative incidence plots of absolute risk of depression after injury. The x-axis shows time after injury, spanning 5 years. The y-axis shows cumulative incidence of depression. Numerical counts indicate the number of patients alive without depression at the corresponding time. Results show increasing incidence of depression with time, modest accentuation after a concussion, and no reduction in risk associated with statin use. Both patient groups show minimal healthy user bias.