[ Watch the Video: Good Hygiene May Be Bad For Your Brain ]
redOrbit Staff & Wire Reports – Your Universe Online
Good hygiene typically leads to good health, but new research appearing in the journal Evolution, Medicine and Public Health suggests that people living in industrialized nations could be more likely to develop Alzheimer’s disease due to cleanliness.
Specifically, Dr. Molly Fox, lead author of the study and Gates Cambridge Alumna, and colleagues report that men and women in those countries have far less contact with bacteria, viruses and other microorganisms. As a result, that could lead to potential problems with the development of their immune systems, as well as an increased risk of dementia.
The research, which was conducted at Cambridge’s Biological Anthropology division, discovered a “very significant” relationship between a country’s wealth and hygiene and the Alzheimer’s-related “burden” placed on its populace, the authors explained. Higher-income, highly-industrialized nations with large urban areas and better disease-prevention practices tend to exhibit far higher rates of the neurodegenerative condition.
Using age-standardized data, which predict Alzheimer’s rates if all countries had the exact same population birth rate, life expectancy and age structure, the researchers discovered strong correlations between national sanitation levels and Alzheimer’s.
They believe that their findings strengthen the dementia-related “hygiene hypothesis” which suggests that sanitized environments in developed countries results in far less exposure to a diverse range of bacteria, viruses and microorganisms. That lack of exposure could cause a person’s immune system to develop poorly, exposing the brain to the inflammation typically linked 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,” Dr. Fox explained. “We believe we can now add Alzheimer’s to this list of diseases. There are important implications for forecasting future global disease burden, especially in developing countries as they increase in sanitation.”
[ Watch the Video: Better Hygiene May Increase Alzheimer’s Risk ]
She and her associates tested whether or not pathogen prevalence could explain the variation in Alzheimer rates across 192 different countries. They first adjusted for differences in population age structures, and then discovered that countries with higher sanitation rates also had higher rates of Alzheimer’s disease.
“For example, countries where all people have access to clean drinking water, such as the UK and France, have 9 percent higher Alzheimer’s rates than countries where less than half have access, such as Kenya and Cambodia,” the university reported. “Countries that have much lower rates of infectious disease, such as Switzerland and Iceland, have 12 percent higher rates of Alzheimer’s compared with countries with high rates of infectious disease, such as China and Ghana.”
“More urbanized countries exhibited higher rates of Alzheimer’s, irrespective of life expectancy. Countries where more than three-quarters of the population are located in urban areas, such as the UK and Australia, exhibit 10 percent higher rates of Alzheimer’s compared to countries where less than one-tenth of people inhabit urban areas, such as Bangladesh and Nepal,” they added.
Differences in sanitation levels accounted for 33 percent of the discrepancy in Alzheimer’s rates between countries, while infectious diseases accounted for 36 percent and urbanization was linked 28 percent. While those trends have “overlapping effects,” the researchers said that they are a good indication of a country’s degree of hygiene.
When combined, they account for 42.5 percent of the “variation” in countries’ Alzheimer’s disease rates. In short, nations with greater levels of hygiene also have far higher dementia-related rates, independent of life expectancy. Previous research had shown that developed countries’ dementia rates doubled every 5.8 years, compared with every 6.7 years in low-income, developing countries.