Based on our analyses, it appears that hygiene is positively associated with AD [Alzheimer's disease] risk. Countries with greater degree of sanitation and lower degree of pathogen prevalence have higher age-adjusted AD DALY rates. Countries with greater degree of urbanization and wealth exhibit higher age-adjusted AD DALY rates.
So far, so fair, right? Well, so far as it goes. As Dr. James Pickett, head of research for The Alzheimer’s Society, toldThe Telegraph,
We have known for some time that the numbers of people with Alzheimer’s varies between countries. That this discrepancy could be the result of better hygiene is certainly an interesting theory and loosely ties in with the links we know exist between inflammation and the disease. However it is always difficult to pin causality to one factor and this study does not cancel out the role of the many other lifestyle differences such as diet, education and wider health which we know can also have a role to play.
Which takes us back to the last sentence of the abstract above. Might these two ginormous variables pack much more of a punch when it comes to Alzheimer’s risk? For urbanization and wealth both increase exposures to environmental toxins of all sorts – through the products we buy, food we eat, water we drink and air we breathe – which research continues to suggest play a role not just in Alzheimer’s, but Parkinson’s and other neurodegenerative disorders. Urbanization and wealth likewise mean greater amounts of conventional medical and dental care, which can further add to one’s toxic burden, as with, perhaps most obviously, mercury amalgam fillings.
That said, hygiene may still play a role. Consider the “hygiene hypothesis” as explained by The Telegraph:
The hygiene hypothesis is based on the assumption that lack of contact with “dirt” in the form of bacteria and other infectious agents upsets the development of white blood cells, key elements of the immune system.
In particular, T-cells are said to be affected. T-cells have a variety of functions, including attacking and destroying foreign invaders and marshalling other parts of the immune system.
Some, known as “regulatory” T-cells, reign in the immune system when it starts to get out of control. Dysfunctional regulatory T-cells can lead to inflammation and autoimmune disorders.
Regulatory T-cell deficiency is linked to the type of inflammation commonly found in the brains of people with Alzheimer’s disease.
The researchers wrote: “Exposure to micro-organisms is critical for the regulation of the immune system.”
It’s just important to remember, all headlines aside, that this is likely just one piece of a larger dynamic. For Alzheimer’s, like most diseases exacerbated by modernity, isn’t like malaria, say, where one specific cause enters a vulnerable body. It’s multifactoral.
You’re not going to solve its problems by dealing with anything less than all contributing factors.