Kolahdouzan M, Hamadeh MJ. The neuroprotective effects of caffeine in neurodegenerative diseases. CNS Neurosci Ther. 23(4) 272-290, 2017.
From the authors: "Caffeine is the most widely used psychostimulant in Western countries. In Alzheimer’s disease, caffeine is beneficial in both men and women, in humans and animals. Similar effects of caffeine were observed in men with Parkinson’s disease; however, the effect of caffeine in female PD patients is controversial due to high levels of estrogen in women. Caffeine is protective in Alzheimer’s disease and Parkinson’s disease at dosages equivalent to 3-5 mg/kg. However, further research is needed to investigate the effect of caffeine on Parkinson’s disease in women. As well, the effects of caffeine in amyotrophic lateral sclerosis, Huntington’s disease and Machado-Joseph disease need to be further investigated."