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Throw Hygiene to the Wind to Reduce Alzheimer's Risk?

Carrie Steckl, Ph.D.: Fri, Sep 20th 2013

In a few weeks, I'll begin teaching an undergraduate research course for aspiring human service professionals. The goal is not so much to teach them how to conduct research; instead, the goal is to help them become good consumers of research - that is, to evaluate whether a study has merit, if the researchers asked a good question, and whether there may be other explanations for the findings. That way, the students will know which studies to rely upon to inform their practice.

hands being washedThe best way to teach skills like this is through real examples. And boy, did I find a great one when I read about a study led by researchers at the University of Cambridge regarding the "hygiene hypothesis" and Alzheimer's disease.

In the study, researchers compared rates of Alzheimer's disease across 192 developed and undeveloped countries. Developed countries by definition have higher degrees of sanitation, lower prevalence of pathogens, higher wealth, and greater levels of urbanization. Undeveloped countries, on the other hand, have lower degrees of sanitation, higher prevalence of pathogens, and lower levels of wealth and urbanization.

They found that the developed countries had higher incidences of Alzheimer's disease than the undeveloped countries. That's fair enough - but it's what they inferred from these findings that blew me away. The researchers claimed that good hygiene raises the risk of Alzheimer's disease.

That's right - apparently being sanitary is bad for your brain. The researchers say that their study supports the "hygiene hypothesis," a popular theory among allergists that over-sanitation practices deflate our immune systems and make us more vulnerable to allergies and autoimmune conditions.

My beef is not with the hygiene hypothesis per se - I admit that it may have merit regarding some health issues and the development of antibiotic resistant germs (quick rule of thumb, folks - alcohol-based hand sanitizers do not contribute to the development of antibiotic resistant bugs, but antibacterial soaps that contain triclosan probably do). Instead, my beef is with the fact that the researchers made a gargantuan leap from their results to their conclusions.

The idea that Alzheimer's is caused by a bacteria, virus, allergy, or other autoimmune malfunction is just one of many theories out there regarding the causes of the disease. The researchers are operating from this rationale in tunnel-style vision without considering the other possible causes of the disease not related to sanitation. Consider that developed countries such as the United States not only have better sanitation than undeveloped countries - they also have:

  • Higher rates of obesity and sedentary behavior
  • Higher levels of sugar and saturated fat in their diets
  • More alcohol abuse
  • Higher exposure to industrial chemicals and other toxins created by infrastructure and technological advances
  • Longer life expectancies

Each of these trends has also been associated with higher rates of Alzheimer's disease - not to mention the fact that developed countries have better medical systems, which means that developed countries probably identify and diagnose Alzheimer's disease at higher rates than undeveloped ones.

Gee - could it be that one of these reasons might also explain the researchers' findings? Or are we locked into the conclusion that Alzheimer's disease occurs more in the United States and similar countries because we are…um…cleaner?

I guess the one person who might have really liked this study is George Carlin. He once said that growing up in New York, he used to swim in the Hudson River while it was replete with raw sewage - and claimed that he never got sick from germs in his life (he died of heart failure in his 70s). If he were alive today, he might just use this study in one of his monologues.


Fox, M., Knapp, L. A., Andrews, P. W., & Fincher, C. L. (2013). Hygiene and the world distribution of Alzheimer's disease: Epidemiological evidence for a relationship between microbial environment and age-adjusted disease burden. Evolution, Medicine, & Public Health, 2013(1), 173-186.

Mahesh, R. (September 6, 2013). Exposure to germs good for health; more hygiene increases risk of Alzheimer's disease. International Business Times:


Carrie Steckl, Ph.D.

Itís a true blessing to have you visit my blog on mental health and wellness. I also write blogs on faith and caregiving in addition to teaching part-time for Columbia College of Missouri. For more information about my background and writing, visit my webpage at

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