Although good hygiene is associated with good health, a new study suggests that people living in industrialized, high income countries may be at risk for developing Alzheimer's disease due to less exposure to bacteria and viruses, effectively weakening their immune systems, ScienceDaily reports.
While it's important to wash your hands and keep them free of germs, doctors also suggest that a little exposure to them, especially during childhood, helps build up the immune system. This is known as the "hygiene hypothesis," suggesting a relationship between cleaner environments and higher risk of allergies and autoimmune diseases.
In the new study carried out at Cambridge's Biological Anthropology division, researchers reported a significant link between a national's sanitation levels and its rates of Alzheimer's disease, a form of dementia that worsens over time. The researchers believe that along with a weakened immune system, the brain may be more prone to inflammation in highly industrialized nations.
"The 'hygiene hypothesis'...is well-established," Molly Fox, lead author of the study, told ScienceDaily. "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."
Fox and her team found that clean drinking water may also be an ironic culprit in developing the brain disease.
In countries such as the U.K. and France where clean water is abundant, the rates of Alzheimer's was 9 percent higher as compared with countries with poorer sanitation such as Kenya and Cambodia. In addition, countries such as Switzerland and Iceland which have lower rates of infectious disease were found to have 12 percent higher rates of Alzheimer's as compared to countries like China and Ghana, nations with high infectious disease rates.
"The increase in adult life expectancy and Alzheimer's prevalence in developing countries is perhaps one of the greatest challenges of our time. Today, more than 50 percent of people with Alzheimer's live in the developing world, and by 2025 it is expected that this figure will rise to more than 70 percent," said Fox. "A better understanding of how environmental sanitation influences Alzheimer's risk could open up avenues for both lifestyle and pharmaceutical strategies to limit Alzheimer's prevalence. An awareness of this by-product of increasing wealth and development could encourage the innovation of new strategies to protect vulnerable populations from Alzheimer's."
Although the trends in data have "overlapping effects," the researchers maintained that differences in sanitation levels are a good indication of a country's hygiene levels.
"Exposure to microorganisms is critical for the regulation of the immune system," the researchers wrote. "Since increasing global urbanization beginning at the turn of the 19th century - the populations of many of the world's wealthier nations have increasingly very little exposure to the so-called 'friendly' microbes which "stimulate" the immune system - due to "diminishing contact with animals, feces and soil."
The new study was published in Evolution, Medicine, and Public Health.
