Middle-age and elderly patients with type 1 diabetes (T1D) are at an increased risk for dementia if they had a traumatic brain injury (TBI), according to study results published in Neurology.

Patients from the Kaiser Permanente Northern California (KPNC) health plan who were age ≥50 (mean age, 57±9.2) and had a recorded diagnosis of T1D were included in the analysis (n=4049). Electronic medical records were reviewed to identify patients with diagnoses of TBI (n=178) and dementia (n=212).

All diagnoses were recorded between 1996 and 2015. Associations between time-dependent TBI and dementia were assessed in analyses adjusted for demographics, nephropathy, glycated hemoglobin, peripheral artery disease, stroke, depression, and dysglycemic events. In addition, the investigators assessed whether or not an association existed between baseline TBI and the risk for dementia.

In the analysis adjusted for demographics, patients with a recorded diagnosis of TBI had a 3.8-times higher risk for dementia compared with patients without TBI (hazard ratio [HR], 3.77; 95% CI, 2.43-5.85).

Further adjustment revealed a persistent association between TBI and increased risk for dementia (HR, 3.64; 95% CI, 2.34-5.68). In Fine and Gray regression models that accounted for competing risk for death, the investigators also found that TBI was associated with an increased dementia risk (HR, 2.91; 95% CI, 1.29-5.68). In addition, a history of TBI at the time of cohort enrollment was associated with a >3-fold risk for dementia (HR, 3.50; 95% CI, 1.58-6.65).

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Limitations of the analysis included the relatively small sample size and the lack of brain imaging to determine the effect of TBI on brain health.

“Lower levels of cognitive reserve may place individuals with T1D at greater risk [for] the deleterious effects of TBI,” the researchers wrote, “which may explain the greater magnitude of dementia associated with TBI in this sample than in prior studies.”

Reference

Gilsanz P, Albers K, Beeri MS, et al. Traumatic brain injury associated with dementia risk among people with type 1 diabetes. Neurology. 2018;91:e1611-e1618.