Head injury increases risk for dementia, with differences according to sex, race
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History of head injury correlated with a greater risk for dementia in a dose-dependent manner, according to results from a community-based cohort study with 25 years of follow-up published in Alzheimer’s & Dementia.
“Head injury is associated with significant morbidity and mortality,” Andrea L. Schneider, MD, PhD, a physician affiliated with the neurocritical care and traumatic brain injury programs at Penn Medicine and an assistant professor of neurology at the University of Pennsylvania, told Healio Neurology. “Less is known about the long-term associations of head injury with dementia, including associations with the number of head injuries and possible differences in the association by sex and race.”
Schneider and colleagues examined data from the ongoing Atherosclerosis Risk in Communities (ARIC) study, a community-based prospective cohort investigation “that is uniquely positioned to investigate the associations between head injury and incident dementia over a median of 25 years of follow-up in a biracial population,” according to the study report. Investigators defined head injury using self-reported injuries and ICD-9/ICD-10 codes and dementia with cognitive evaluations, interviews with participants and ICD-9/ICD-10 codes from death certificates.
The present analysis included 14,376 participants, with a mean age of 54 years at baseline (56% women; 27% Black). Researchers categorized 1,866 head injury/injuries from self-report alone, 1,081 head injury/injuries from hospitalization data alone and 493 head injury/injuries from both sources. This translated to nearly a quarter of patients in the study having head injuries (24%), according to the study results.
Schneider and colleagues found that head injury correlated with risk for dementia (HR = 1.44; 95% CI, 1.3-1.57), with evidence of a dose response related to number of head injuries (one head injury, HR = 1.25; 95% CI, 1.13-1.39; two or more head injuries, HR = 2.14; 95% CI, 1.86-2.46). Researchers also found evidence for stronger relationships between head injury and risk for dementia among women (HR = 1.69; 95% CI, 1.51-1.9) vs. men (HR = 1.15; 95% CI = 1-1.32; P for interaction < .001) and among white participants (HR = 1.55; 95% CI, 1.4-1.72) compared with Black participants (HR = 1.22; 95% CI, 1.02-1.45; P for interaction = .008). They observed no difference in the association between head injury and dementia according to age, according to Schneider.
“Our findings suggest that head injury is more strongly associated with risk for dementia among women compared with men and among whites compared with Blacks,” she said. “Further investigation of sex and race differences in dementia risk after head injury in diverse populations is warranted, with a particular focus on contributions from socioeconomic and vascular risk factors for dementia. It is also important to consider that the types and severities of head injuries sustained may be different by sex and race, which may contribute to the observed differences in risk.”
Schneider also highlighted the potential clinical implications of the results.
“The strength of the association of increasing numbers of head injuries with dementia risk is significant and suggests that prevention of head injury could potentially mitigate some risk for dementia later in life,” she said. “However, it is important to remember that head injury is not the only risk factor for dementia. High blood pressure and diabetes, among other factors, also contribute significantly to dementia risk, but head injury is one risk factor for dementia that is modifiable by behavior changes, such as wearing helmets and seat belts.”