CSF Aβ42 predicts early-onset dementia in Parkinson disease

Objective:To test in vivo the proposal from clinicopathologic studies that -amyloid (A) pathology shortens the time to dementia in Parkinson disease (PD), and to explore the utility of CSF A and related measures as early prognostic biomarkers of dementia in an incident PD cohort.Methods:We assessed a population-based incident cohort of 104 patients with PD who underwent lumbar puncture at diagnosis. We analyzed CSF concentrations of A42, A40, and A38 using a multiplexed immunoassay with electrochemiluminescence (ECL) detection and levels of A42, total tau, and phosphorylated tau using ELISA. Patients were followed prospectively for 5 years. Dementia was diagnosed according to published criteria.Results:CSF levels of A42 were significantly decreased in patients who developed dementia (n = 20, 19.2%) compared to those who did not (n = 84, 80.8%), as measured by ECL (-33%, p = 0.006) as well as ELISA (-36%, p < 0.001). No differences were observed for other markers. Low A42 values predicted a substantially increased risk for subsequent dementia at high sensitivity (85%), with hazard ratios of 9.9 (95% confidence interval 2.3-43.5, p = 0.002) for A42(ECL) <376 pg/mL and 7.6 (2.2-26.4, p = 0.001) for A42(ELISA) <443 pg/mL, after adjustment for baseline age and PD-mild cognitive impairment (MCI) status. A42 reductions tended to precede the onset of PD-MCI that progressed to dementia.Conclusions:These in vivo data support the role of A pathology in the etiology and highlight the potential utility of CSF A42 as an early prognostic biomarker of dementia associated with PD.