Haven't time for a full answer but be aware that the reason Vitamin D is so important for Neuroprotection is because it upregulates the production of glutathione as indeed does the improvement of melatonin secretion.
The trouble with getting older (and I'm starting at 35yrs and older) is that our natural ability to secrete both Vitamin D3 AND Melatonin declines year on year therefore we have to try harder to ensure we get UVB exposure over all our skin surface and improve our circadian rhythm (bright light daytime, subdued light evening, pitch dark bedrooms) or understand how best to use the relevant supplements effectively. If we leave neuroprotection until the point we notice symptoms of cognitive impairment it is too late.
We will have lost 70% of our brain capacity and have set in motion the cascade of consequences from which there is no return and the best we can hope for is to slow the inevitable decline and to be honest I've made it clear that if I lose my ability to think/act for myself I'd rather not have any future life that I was not sufficiently cognisant to enjoy or be aware of lengthened unnecessarily.
So the time for vitamin D, melatonin, coconut oil, curcumin, resveratrol, omega 3 and green tea (all neuroprotective) along with exercise where possible, is NOW. Don't wait till it's too late.
It's also worth pointing out that these are all anti oxidants as well as anti inflammatory agents. We can all reduce the potential for oxidation by donating blood regularly. Particularly menopause for women should be the time to start donating regularly to maintain the advantage women have while reducing iron overload in monthly periods. If men want to live as long as women they should start donating blood as teenagers and continue as long as possible.