Peripheral Nerve Conduction in Alzheimer's vs. Late-Life Depression: A Comparative Study

Alzheimer's disease (AD) and late-life depression (LLD) patients both exhibit peripheral motor nerve conduction impairments, but with distinct patterns, highlighting divergent neurophysiological mechanisms in these aging-related disorders.

To compare peripheral nerve conduction function among normal cognition (NC), older adults with AD, and LLD.

All the participants were enrolled and assigned to AD, LLD and aged-matched NC controls (all ≥60 years, n=60, respectively). Sensory conduction of the median and sural nerves, and motor conduction of the median and common peroneal nerves, were assessed. Key parameters included latency, amplitude, and conduction velocity. Group differences were analyzed after adjusting for gender, age, education, height, and comorbid medical conditions.

By controlling gender, age, height, education level, and somatic diseases with inter-group differences, compared with NC group, the median nerve motor conduction in AD group showed prolonged proximal latency (3.21 vs. 3.65 ms, P=0.023), reduced amplitude (proximal: 7.30±2.02 vs. 3.89±0.57 mV; distal: 6.13±2.17 vs. 4.12±2.38 mV, both P<0.001), and slowed conduction velocity (56.46±5.18 vs. 49.29±6.27 m/s, P=0.002). LLD group exhibited more pronounced latency prolongation (proximal: 3.21 vs. 4.06 ms; distal: 7.18 vs. 7.98 ms, both P<0.001) and greater amplitude reduction (proximal: 7.30±2.02 vs. 3.65±0.66 mV; distal: 6.13±2.17 vs. 3.18±1.88 mV, both P<0.001). In terms of the common peroneal nerve motor conduction, function AD group had significantly slower conduction velocity (48.88±5.82 vs. 42.85±5.27 m/s, P=0.033). LLD group showed prolonged proximal latency (4.25 vs. 5.77 ms, P<0.001). No significant differences were found in sensory conduction parameters across groups after adjustment.

Both AD and LLD groups were associated with peripheral motor neuropathy, but the pattern of impairment differs. AD is marked by generalized conduction slowing, while LLD shows more severe latency delays and amplitude loss, suggesting distinct pathophysiological pathways. These findings provide new insights into the peripheral nervous system's involvement in age-related neurocognitive and mood disorders.