Peripheral nerve function and dementia in older adults with and without diabetes

Abstract

AbstractBackgroundFew studies have focused on sensory peripheral nerve impairment as risk factor for or marker of dementia, although other sensory impairments are associated with cognitive decline. Peripheral nerve impairments are higher with aging, musculoskeletal injury, and conditions such as diabetes, which in turn may accelerate cognitive decline. We evaluated whether sensory nerve impairment in older adults was associated with higher risk of dementia and examined differences by diabetes status.MethodWe studied 1,923 black and white non‐demented participants from Health, Aging, and Body Composition (Health ABC) Study who were aged 70‐79 at 1998/99 enrollment (52% women; 35% black). Sensory nerve tests evaluated in Year 4 (2000/01) included monofilament (1.4‐g, 10‐g) and vibration threshold of the toe. Monofilament insensitivity was defined as unable to detect monofilament (3/4 touches) and poor vibration threshold was defined as >130μm. Incident dementia (over 11 years of follow‐up) was based on hospitalization records, dementia medications, or ≥1.5 SD decline in Modified Mini‐Mental State Exam score (race‐specific). Cox proportional hazard models with adjustment for demographics, comorbid health conditions, and health behaviors evaluated risk of dementia associated with peripheral nerve impairments. We tested for interactions with diabetes status.ResultOf older participants, 44.7% had 1.4‐g monofilament insensitivity, 8.3% had10‐g monofilament insensitivity, and 5.9% had poor vibration threshold. 1.4‐g monofilament insensitivity was not associated with dementia (HR: 1.14, 95% CI: 0.92, 1.40), either in the combined group or by diabetes status (interaction with diabetes p=0.78). 10‐g monofilament insensitivity was associated with higher risk of dementia in those with diabetes (HR: 2.52; 95% CI: 1.53, 4.14) but not those without diabetes (HR: 1.00; 95%CI: 0.63, 1.60) (p=0.02 for interaction). Poor vibration threshold was associated with higher risk of dementia in those without diabetes (HR: 1.72, 95%CI: 1.15,2.60), estimates were elevated but not significant in those with diabetes (HR: 1.31; 95%CI: 0.48,4.49), and the interaction by diabetes was not significant (p=0.50).ConclusionSensory nerve impairments were associated with increased risk of dementia although the effects differed by diabetes status. These associations may represent shared risk factors that affect peripheral and central nervous system degeneration.