Although it remains possible that higher B12 levels are a nonspecific marker of better health status, we speculate that higher B12 levels may slow deterioration of gait either by reducing the development of neuropathy/myelopathy because of its known effect on nervous system myelination or possibly by affecting PD pathogenesis by reducing LRRK2 activity.4 Interestingly, prior studies have shown that B12 levels are lower in early PD19, 20 and decline more rapidly than expected in normal aging,20, 21 possibly because of reduced gastrointestinal absorption.22, 23. This evidence concerns the gene LRRK2 and Parkinson disease.