Table 2 Overview of blood melatonin levels in AD as compared to controls. ↓ means a significant reduction in blood melatonin in AD when compared to controls. ↑ means a significant increase in blood melatonin in AD when compared to controls. = means no significant difference in pineal melatonin in AD when compared to controls. ✖ means no data comparing blood melatonin levels between AD and controls were available. A black star ★ was attributed per NOS criterium per category (selection, comparability, exposure) met. Stars were kept white ☆ if the NOS criterium in the corresponding category was not met

From: Melatonin levels in the Alzheimer’s disease continuum: a systematic review