Diabetes, peripheral neuropathy, and old age disability

The purpose of this study was to determine whether peripheral neuropathy explains the apparent association between diabetes and disability in old age, and to evaluate the utility of lower extremity function tests in older diabetic adults with and without neuropathy. We evaluated 39 adults, aged 70-79 years, for pressure sensation (log(10)g), vibration perception threshold (VPT; microns), and electrophysiologic function of the peroneal nerve. The subjects included patients with established diabetic neuropathy (DN; n = 14), diabetic controls without neuropathy (DC; n = 13), and nondiabetic controls (NDC; n = 12). Nonparametric statistical methods were used to relate neuropathy measures to performance in tests of walking speed, static and dynamic balance, coordination, and ankle strength (kilograms). Significant age-adjusted correlations were observed between measures of sensory neuropathy and a variety of performance measures, and electrophysiologic measures were related to static balance. DN subjects had significantly higher pressure sensation than NDC (5.17 vs 3.38g, P < 0.05), higher VPT (62.5 vs 21.7 microm, P < 0.05), and lower peroneal motor response amplitudes at multiple sites. Pressure sensation and nerve conduction measures did not differ between DC and NDC. Compared with NDC, DN subjects performed significantly worse on tests of walking speed (0.99 vs 1.34 m/s; P < 0.05), static balance (4.9 vs 20.4 s; P < 0.05), dynamic balance (9.23 vs 25.52 s; P < 0.05), and coordination (6.73 vs 4.76 s; P < 0.05). No differences were observed in these measures between DC and NDC. Observed differences in physical abilities between older diabetic and nondiabetic adults may have been due to the subset of diabetic individuals with peripheral neuropathy. Quantitative measures of sensory and motor nerve function have distinct effects on physical performance. Interventions aimed at reducing the impact of diabetes-associated disability in old age may have the greatest impact among people with peripheral neuropathy.