Object Mild traumatic brain injury (TBI) has been proposed as a risk factor for development of Alzheimer’s disease, Parkinson’s disease, depression, and other illnesses. This study’s objective was to determine the association of prior mild TBI with subsequent diagnosis (i.e., at least one year post-injury) of neurologic or psychiatric disease. Methods All studies from 1995–2012 reporting TBI as a risk factor for diagnoses of interest were identified by searching PubMed, study references, and review articles. Reviewers abstracted the data and assessed study design and characteristics. Results 57 studies met inclusion criteria. A random effects meta-analysis revealed a significant association of prior TBI with subsequent neurologic and psychiatric diagnosis. The pooled odds ratio (OR) for TBI on development of any illness was 1.67 (95% CI 1.44–1.93, p<.001). Prior TBI was independently associated with both neurologic [OR 1.55 (95% CI 1.31–1.83, p<.001)] and psychiatric [OR 2.00 (95% CI 1.50–2.66, p<.001)] outcomes. Analyses of individual diagnoses found higher odds of Alzheimer’s disease, Parkinson’s disease, mild cognitive impairment, depression, mixed affective disorders, and bipolar disorder in individuals with previous TBI compared to those without TBI. This association was present when examining only studies of mild TBI and when considering the influence of study design and characteristics. Analysis of a subset of studies found no evidence that multiple TBIs were associated with higher odds of disease than a single TBI. Conclusions History of TBI, including mild TBI, is associated with the development of neurologic and psychiatric illness. This indicates that either TBI is a risk factor for heterogeneous pathologic processes or that TBI may contribute to a common pathologic mechanism.

Despite the strong relationship seen between comorbid conditions and onset of frailty, this observational study suggests that participation in self-selected exercise activities is independently associated with delaying the onset and the progression of frailty. Regular exercise should be further examined as a potential factor in frailty prevention for older adults.

Objective We aimed to determine whether hearing impairment (HI) in older adults is associated with the development of frailty and falls. Method Longitudinal analysis of observational data from the Health, Aging and Body Composition study of 2,000 participants aged 70 to 79 was conducted. Hearing was defined by the pure-tone-average of hearing thresholds at 0.5, 1, 2, and 4 kHz in the better hearing ear. Frailty was defined as a gait speed of <0.60 m/s and/or inability to rise from a chair without using arms. Falls were assessed annually by self-report. Results Older adults with moderate-or-greater HI had a 63% increased risk of developing frailty (adjusted hazard ratio [HR] = 1.63, 95% confidence interval [CI] = [1.26, 2.12]) compared with normal-hearing individuals. Moderate-or-greater HI was significantly associated with a greater annual percent increase in odds of falling over time (9.7%, 95% CI = [7.0, 12.4] compared with normal hearing, 4.4%, 95% CI = [2.6, 6.2]). Discussion HI is independently associated with the risk of frailty in older adults and with greater odds of falling over time.

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