Vitamin B12 and homocysteine levels and 6-year change in peripheral nerve function and neurological signs.

BACKGROUND: Low vitamin B12 and high homocysteine (Hcy) levels are common in older adults and may be associated with worse neurological function. The aim of this study is to determine whether changes in B12 or Hcy levels are associated with longitudinal changes in peripheral nerve function and clinical neurological signs and symptoms. METHODS: Participants aged 60 years and older at baseline (n = 678; 72.2 +/- 6.2 years; 43.5% male) were from the InCHIANTI Study. Low B12 (/=13 mumol/L) were measured at baseline and 3-year follow-up. Neurological function was assessed by peroneal nerve conduction amplitude (compound motor action potential) and velocity, neurological examination, and peripheral neuropathy symptoms at baseline, 3-year, and 6-year follow-up. RESULTS: At baseline, 43.8% had low B12 levels and 58.6% had high Hcy levels. Over 6 years, 12.4% declined to poor compound motor action potential (<1 mV) and 42.1% declined to poor nerve conduction velocity (