As the global population ages, the incidence of traumatic brain injury (TBI) increases. While mild TBI can impair the cognitive function of older adults, the cause and background of mild TBI-induced cognitive impairment remains unclear, and the evaluation of risk factors for cognitive impairment after mild TBI remain open for consideration especially in the current aging society. This study aimed to evaluate the risks associated with cognitive impairment following mild TBI.
Between January 2006 and December 2018, 2,209 patients with TBI required hospitalization in Shimane Prefectural Central Hospital. Mild TBI was defined as a Japan coma scale ≤ 10 at admission. The cognitive function of the patients was measured with the Hasegawa Dementia Rating Scale-revised or Mini-mental state examination at least twice during the patients’ hospital stays. The odds ratio (OR) and 95% confidence interval (CI) of each considered risk factor was calculated with multivariable logistic regression analysis after univariate analysis.
Among 1,674 patients with mild TBI, 172 patients underwent cognitive function examinations, and 145 patients (84.3%) were found to have cognitive impairment at discharge. Significant risk factors for cognitive impairment included age (P = 0.008) and hypertension (P = 0.013) in univariate analysis; and age (OR 1.04: 95% CI 1.01-1.07) and hypertension (OR 5.81: 95% CI 1.22-27.68) by multivariable analysis.
Older patients with hypertension displayed significantly higher cognitive impairment risk after even mild TBI. For these patients, we should take carefully management even after mild TBI.

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