A new study has found higher rates of Alzheimer’s in higher-income, industrialized countries. Headed by Cambridge University, researchers have posited an interesting hypothesis: Due to reduced contact with bacteria, people living in sanitized, developed countries may have less developed immune systems, which may be a risk factor for 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. Molly Fox, lead author of the study, said. “We believe we can now add Alzheimer’s to this list of diseases.”
The study looked at the percentage of people with access to clean drinking water, or the percentage of people living in cities in various countries. “We find that countries that are less urbanized, with more pathogens and lower degree of sanitation have lower Alzheimer’s rates,” the study states in its summary.
While completing her Ph.D. at Cambridge University supported by the Gates Foundation, Fox said she studied Alzheimer’s in the context of Darwinian medicine, a perspective that employs “the tools of evolutionary biology towards understanding human health and disease.”
Although it is a unique perspective on one possible factor for Alzheimer’s disease, many remain skeptical of Fox’s findings. This is not the first time that researchers have found a higher rate of Alzheimer's and other diseases in sanitized, developed countries and concluded that there may be a relation between hygiene and less-developed immune systems.
Melanie Haiken of Forbes points out that the Alzheimer’s hygiene hypothesis is just a theory. Fox's study proves only an association, not a causation. Haiken also notes that there’s still a debate over whether Alzheimer’s can be considered an immune-related disease.
Simon Ridley, head of research at Alzheimer’s Research UK, told WebMD Health News that the study is “intriguing” but that the risk of Alzheimer’s “is likely to be influenced by a complex mix of environmental and lifestyle factors.”
"This study did not investigate whether other factors beyond hygiene may be linked to any differing Alzheimer’s risk in different countries," Ridley said.