Melatonin and the pineal glands that secrete it are possibly related to the pathology of Alzheimer’s disease (AD). Melatonin affects amyloid, tau and inflammation.1 Its secretory capacity is positively correlated with pineal parenchymal volume (PPV), and its synthesis is associated with mitochondrial volume in pinealocytes.2 Pineal volume reduction has been identified in AD3 and has been shown to already appear by the mild cognitive impairment (MCI) stage.4 However, whether pineal volume reduction occurs in other neurodegenerative diseases is unknown. Since a review indicated that the antioxidant effect of melatonin might be involved in both AD and Parkinson’s disease (PD),5 pineal volume reduction might also be associated with Lewy body disease. This study aimed to investigate pineal volume reduction in AD and PD.

Data were acquired from the Parkinson’s and Alzheimer’s Disease Dimensional Neuroimaging Initiative (https://padni.org/) database. Overall, 147 individuals were included in this study (online supplemental figure 1).

[jnnp-2023-332252supp002.pdf]

The diagnoses were established by neurologists or psychiatrists at each institution. Clinical diagnoses of participants included AD spectrum (preclinical AD, MCI due to AD, or AD), PD spectrum (prodromal PD/dementia with Lewy bodies (DLB), PD or DLB), MCI unlikely due to AD, and cognitively normal.

All participants underwent brain MRI for 3.0-T T1-weighted three-dimensional magnetisation-prepared rapid gradient-echo imaging. Brain MRI data were acquired using the following parameters: repetition time, 2500 ms; echo time, 2.18 ms; inversion time, 1000 ms; resolution, 0.8×0.8×0.8 mm; field of …