Higher prevalence of neuropathy has been described in patients with
Parkinson's disease (PD) in comparison with age and gender-matched controls. The cause of neuropathy may be
levodopa-induced impairment of
vitamin B12 metabolism, suggesting
levodopa-naïve subjects should be unaffected. There may, however, be other yet unidentified determinants of neuropathy in PD. We screened 33 consecutive
levodopa-naïve PD patients for neuropathy. Demographics,
vitamin B12 and
folate levels were studied. Findings were analyzed in the light of our previous available data on
levodopa-treated PD patients. Four of 33 (12.1 %)
levodopa-naïve PD patients were diagnosed with neuropathy. This compared to 13/36 (36.1 %) previously evaluated
levodopa-treated patients (p = 0.027) and 3/37 controls (p = 0.7). Analysis of our whole PD cohort consisting of a total of 70 subjects, including
levodopa-naïve and
levodopa-treated patients, revealed that neuropathy correlated with use of
levodopa (p = 0.041), cumulative
levodopa exposure (p = 0.046), age at time of study (p = 0.005) and serum
folate levels <10 μg/L (p = 0.003). There was no association of neuropathy with PD duration. Multivariate regression analysis showed that neuropathy was only independently associated with age (p = 0.016) and serum
folate levels <10 μg/L (p = 0.012). We conclude that this study confirms the roles of
levodopa usage and cumulative
levodopa exposure in the neuropathy of PD. However, the effects of
levodopa only appear contributory and are surpassed by age and lower
folate levels. In view of the independent implication of lower
folate levels, the need for preventative/protective supplementation including
folate in addition to
vitamin B12, probably irrespective of
levodopa use, may deserve consideration in patients with PD.