Dr Robert Sapolsky just posted an authoritative and helpful talk on YouTube which looks at possible causes of Alzheimer's, prospective treatments, and practical steps to minimise one's risk.I found it a fascinating and entertaining video. It probably has some relevance to Parkinson's, but in any case I am going to ask him to take a similar look at PD.
Sapolsky is a Stanford professor specialising in neuroscience, endocrinology and primatology, apparently, so no lightweight!