Plasma ascorbate concentrations relative to cognitive function. (A) MoCA (Montreal Cognitive Assessment) scores in the Parkinson’s disease group (n = 212) showed a significant positive correlation with ascorbate status (r = 0.14, p = 0.045). (B) Plasma ascorbate concentrations in individuals with Parkinson’s disease as per cognitive status subgroups: normal (PD-N, n = 95), mild cognitive impairment (PD-MCI, n = 84), and dementia (PD-D, n = 34); the cognitively impaired group (PD-MCI and PD-D combined, n = 118) was significantly lower than the PD-N group (p = 0.03). Box plots show medians with boundaries set at 25th and 75th percentiles, whiskers at 5th and 95th percentiles, outliers are indicated by symbols.