Better hygiene in wealthy nations may have played a part in increased rates of Alzheimer's disease, researchers have claimed.
Populations in high income, more urbanised and highly industrialised countries have higher rates of Alzheimer’s disease.
A new study from the University of Cambridge has suggested that this could be because better hygiene in these areas has greatly reduced contact with bacteria and viruses, leading to poorly developed immune systems that leave the brain more exposed to the inflammation associated with Alzheimer’s disease.
“The ‘hygiene hypothesis’, which suggests a relationship between cleaner environments and a higher risk of certain allergies and autoimmune diseases, is well- established. We believe we can now add Alzheimer’s to this list of diseases,” said Dr Molly Fox, lead author of the study.
Researchers analysed Alzheimer’s rate in 192 countries, and applied age standardisation to remove differences in birth rate, life expectancy and population age structure from the equation. After adjusting they found that countries with higher levels of sanitation had higher rates of Alzheimer’s.
Different levels of sanitation, infectious disease and urbanisation accounted for 33 per cent, 36 per cent and 28 per cent of the discrepancy in Alzheimer’s rates between countries respectively, researchers said.
However, the Alzheimer’s Society cautioned against pinning the causes of dementia to one factor.
“We have known for some time that the numbers of people with Alzheimer’s varies between countries,” a spokesperson said. “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.”