Concussion Associated With Greater Risk of Parkinson Disease, Dementia

Individuals who had experienced a concussion were found to be at a greater risk of Parkinson disease (PD), mood and anxiety disorders (MADs), dementia, and hyperactivity disorder, with concussed women indicated as a notable at-risk population for MADs, according to study findings published today in Family Medicine and Community Health.

In recent years, the incidence of concussions has steadily increased, the researchers noted, especially among adolescents. Notably, related effects of concussions have been indicated as dysregulation of the autonomic nervous system, cerebral blood flow, and cerebral metabolism.

While these effects may seem troubling, the clinical recovery from concussions typically occurs within the first week of injury. However, the long-term implications of concussions remain unknown.

In previous research, the study authors highlighted that potential associations with increased risk of attention-deficit hyperactivity disorder (ADHD), depression, anxiety, dementia, and PD are limited by study design factors such as a reliance on self-reported medical history and the inclusion of all forms of traumatic brain injuries.

“Other common limitations include a failure to account for either pre-existing health conditions, the time between incident concussion and subsequent diagnosis of conditions of interest, or the occurrence of repeat mild traumatic brain injuries/concussions,” expanded the study authors.

Researchers sought to further investigate these associations by conducting a retrospective population-based cohort study that included 47,483 people who were diagnosed with a concussion from 1990 to 1991 and followed up later in life (2014-2015).

The study’s primary objective served to delineate the associations between concussion and subsequent diagnoses of ADHD, MADs, dementia, and PD, with secondary analyses focusing on the effects of sex, multiple concussions, and diagnosis of other conditions of interest.

Concussed participants (men, n = 28,021; women, n = 19,462) were matched at a 1:3 ratio with healthy controls (men, n = 81,871; women, n = 57,159) based on age, sex, and geographical location. Associations were assessed via stratified Cox proportional hazards regression model that were adjusted for socioeconomic status and pre-existing medical conditions.

In the study findings, those who had experienced a concussion were found to be at a 39% greater risk of ADHD (adjusted hazard ratio [aHR] = 1.39; 95% CI, 1.32-1.46; P < .001), 72% greater risk of MADs (aHR = 1.72; 95% CI, 1.69—1.76; P < .001), 72% greater risk of dementia (aHR = 1.72; 95% CI, 1.61-1.84; P < .001), and 57% greater risk of PD (aHR = 1.57; 95% CI, 1.41-1.75; P < .001).

When examining how the prevalence of multiple concussions affected risks of examined conditions compared with 1 concussion, a second concussion was linked with a heightened risk of dementia by 62% (hazard ratio [HR] = 1.62; 95% CI, 1.25-2.10) and 3 or more concussions were linked with a greater risk of MADs (HR = 1.22; 95% CI, 1.01—1.47) and PD (HR = 3.27; 95% CI, 1.63–6.59).

Additionally, in examining MADs based on sex, women were 28% more likely than men to subsequently become hyperactive and 7% more likely to become depressed or anxious after a concussion.

The researchers noted that as findings are specific to the study cohort, further research is warranted to examine other populations. “Moreover, future studies could expand on our findings by including chart reviews to confirm clinical diagnoses of concussion, adjusting for familiarity of conditions of interest, and long-term prospective follow-up of individuals following incident concussion,” concluded the study authors.

Reference

Morissette MP, Prior HJ, Tate RB, et al. Associations between concussion and risk of diagnosis of psychological and neurological disorders: a retrospective population-based cohort study. Fam Med Com Health. Published online July 27, 2020. doi:10.1136/fmch-2020-000390