Relationship Between Vitamin B12 and Sensory and Motor Peripheral Nerve Function in Older Adults

Objectives To examine whether deficient B12 status or low serum B12 levels are associated with worse sensory and motor peripheral nerve function in older adults. Design Cross-sectional. Setting Health, Aging and Body Composition Study. Participants Two thousand two hundred and eighty-seven adults aged 72 to 83 (mean 76.5 +/- 2.9; 51.4% female; 38.3% black). Measurements Low serum B12 was defined as serum B12 less than 260pmol/L, and deficient B12 status was defined as B12 less than 260pmol/L, methylmalonic acid (MMA) greater than 271nmol/L, and MMA greater than 2-methylcitrate. Peripheral nerve function was assessed according to peroneal nerve conduction amplitude and velocity (NCV) (motor), 1.4g/10g monofilament detection, average vibration threshold detection, and peripheral neuropathy symptoms (numbness, aching or burning pain, or both) (sensory). Results B12-deficient status was found in 7.0% of participants, and an additional 10.1% had low serum B12 levels. B12 deficient status was associated with greater insensitivity to light (1.4g) touch (odds ratio=1.50, 95% confidence interval=1.062.13) and worse NCV (42.3 vs 43.5m/s) (beta=-1.16, P=.01) after multivariable adjustment for demographics, lifestyle factors, and health conditions. Associations were consistent for the alternative definition using low serum B12 only. No significant associations were found for deficient B12 status or the alternative low serum B12 definition and vibration detection, nerve conduction amplitude, or peripheral neuropathy symptoms. Conclusion Poor B12 (deficient B12 status and low serum B12) is associated with worse sensory and motor peripheral nerve function. Nerve function impairments may lead to physical function declines and disability in older adults, suggesting that prevention and treatment of low B12 levels may be important to evaluate.