This article, though it focuses on middle-aged women and it reports only modest (if even statistically significant) cognitive benefits, suggested to me and made me suspicious of the possibility that ginger is a good adjunctive therapy for age-related cognitive decline, which research increasingly suggests begins already in the 3rd decade of life (starting at, if not before, age 20).
One popular and undisproven (and controversial) theory is that all substances which significantly enhance cerebral blood-flow will significantly enhance cognition, due specifically and primarily to the enhanced blood-flow, and only incidentally and secondarily due to other mechanisms (such as acetylcholinerase inhibition, or COX inhibition). This would potentially explain why ginkgo, piracetam, vinpocetine, hydergine, exercise, potentially aspirin, and others are observed to be anti-dementia and pro-cognition. Evidently, these substances have drawbacks and side-effects, some documented, some perhaps unknown, and 6-gingerol might as well have its dark side.
The antithetical and competing theory claims that blood delivery above and beyond homeostatic levels encourage more oxidative stress, due perhaps to increasing oxygen equilibrium in the brain. It could also increase inflammation by promoting the spread of pathogens to neurons or by delivering more white blood cells and inflammatory compounds to the brain. These theories are also undisproven. However, abstaining from exercise and indulging in alcohol (reported to be vasoconstrictive at higher doses, and vasodilative only at lower doses) do not seem to confer dementia patients any profound benefits, thereby delivering a harsh blow to this theory.
My idea is that these observed benefits to cognition (though very small) are due to enhanced cerebral blood-flow, perhaps via anti-platelet activity. Ginger is well-documented to have blood-thinning properties. Could this strongly or even modestly improve cognition?
I juice 2-3 grams of ginger daily since it is purported to attenuate chronic inflammation related to arthritis, heart disease, asthma, cancer and more. If it were also conferring a mild, long-term cognitive boost, I would have no complaints. My fear though is that it is potentially doing more harm than good.