Is The Developed World So Hygienically Clean That It’s Making Us Sick?

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Few would argue the overall health benefits of living in the industrialized world. Clean drinking water, fewer fatal accidents and greatly reduced infant mortality are just a few of the advantages. So pronounced are the health boons of development that researchers may sometimes be blinded to health risks that it brings.

For example, rates of Alzheimer’s disease are higher in developed nations — a fact that is often attributed to the longer life expectancies in those countries. But the higher rates persist even after correcting for longer lifespans, according to a recent study led by Cambridge evolutionary biologist Molly Fox.

With that in mind, it seems there must be health threats in the developed world that aren’t present in countries that have stuck to their agrarian traditions. Fox’s study suggested that, paradoxically, the improved sanitation in developed countries may leave residents more exposed to Alzheimer’s disease.

The study is apparently the first to link Alzheimer’s disease to an increasingly accepted theory called the hygiene hypothesis.

The hypothesis posits that people in industrialized societies don’t come into contact with enough bacteria to spur their immune systems to develop fully. Some, like Fox, focus on the development of germ-killing T-cells in young children.

The hygiene hypothesis has previously been cited as a possible cause for autoimmune disorders, allergies, asthma and even diabetes — all of which have increased rapidly enough to defy conventional explanations.

“In the modern developed world, we live in hygienically sanitized environments, and as a result we’re not in contact with animals, feces and mud, which would have been the norm for the vast majority of human history,” Fox said in a video about the findings, published in published in Evolution, Medicine and Public Health.

Industrialization freed us not just the bacteria that cause fatal bouts of diarrhea in the developing world, but also bacteria with which humans have co-evolved to have a symbiotic relationship, such as those that dwell in healthy intestinal systems and may help keep us thin.

Fox and her co-authors specifically linked better sanitation with higher rates of Alzheimer’s disease. They identified countries with poor water sanitation systems, large rural populations and high rates of infectious disease, all of which indicate that residents come into contact with more microbes. Then they compared those countries’ rates of Alzheimer’s disease with those of developed countries, adjusting for life expectancy. They found that differences in levels of sanitation, infectious disease and urbanization accounted statistically for about a third of the discrepancy in Alzheimer’s rates between countries.

The findings, while more suggestive than conclusive, jibe with some recent medical research into Alzheimer’s disease.

shutterstock_RadiokafkaResearchers have focused on the inflammation found in the brains of those who suffer from Alzheimer’s disease, and the middling immune systems attributed to the hygiene hypothesis are blamed for excessive inflammation. Other recent Alzheimer’s research has identified the failure of the brain’s immune function to “take out the trash” that accumulates from normal cell function.

If medical and public health research support a similar cause for the disease, it may guide them to more successful new prevention and treatment prospects.

“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 disease,” Fox told Singularity Hub.

Real answers about Alzheimer’s disease are still seemingly far off. But the growing body of research across individual diseases backing the hygiene hypothesis could bring new ideas about how industrializing countries might share in the benefits of development without battling microbes as zealously as the West once did.

Photos: hxdbzxy and Radiokafka via Shutterstock.com

Discussion — 12 Responses

  • ledotter September 18, 2013 on 2:21 pm

    “The hygiene hypothesis has previously been cited as a possible cause for autoimmune disorders, allergies, asthma and even diabetes — ALL OF WHICH HAVE INCREASED RAPIDLY ENOUGH TO DEFY CONVENTIONAL EXPLANATIONS.

    Each of the conditions/diseases mentioned has an identified causal genetic component so it would be much more likely that it is not just a matter of better hygiene but more likely due to developed societies opting out of the natural selection process!

    Diabetes was slowly becoming less prevalent until the development of insulin guaranteed the survival of childhood diabetics well past reproductive age. Vaccinations and antibiotics have allowed children with autoimmune, allergies, asthma and, yes, even autism to survive the previously fatal infectious diseases of childhood to pass on their genes. When I was struggling to raise my autistic, immune deficient daughter, I asked my grandmother how these kids were dealt with in the past. Her reply makes sense: “Children like your daughter were called “frail” and seldom survived the first measles, mumps, diphtheria or whooping cough epidemic! We mothers knew which of our children were the frail, vulnerable ones – we spoiled them a bit more than the others because we knew they weren’t going to be with us for long.”

    • 4ndy ledotter September 22, 2013 on 10:53 am

      If you had studied modern genetics or much else in the way of human developmental biology, you would know that the words ‘genetic’ and ‘causal’ do not go together when speaking about disease unless you are referring to some very specific protein-coding deficiency, such as phenylketonuria, albinism, or cystic fibrosis, or more serious genetic disorders like Down’s Syndrome.
      Those disorders mentioned in the article, and especially complex psychological conditions such as autism which you mentioned, come about through gene-environment interactions (as does just about every other complex feature of a living organism). They have “increased rapidly enough” that their spread cannot be accounted for by your eugenicist argument, because there was not enough time for faulty genetic traits to spread amongst the population the way you suggest. Even if they had spread that way, we have far more pressing problems for humanity’s sustainability in infrastructure than in congenital diseases. Educated people tend to avoid conceiving if they are aware of having a congenital disorder anyway, as a personal ethical choice for their children’s sake, so increasing science education is important for solving that problem, not letting people die painfully when it can be avoided.

      Your grandmother is not an expert on epidemiology.

      • ledotter 4ndy September 22, 2013 on 1:16 pm

        4ndy, your assumptions about my knowledge of genetics and your ignorance of recent studies linking specific genetic abnormalities with an increased chance of autistic behavior (and many other diseases) leads me to suggest you do some reading of the most up to date information on the human genome project – https://www.nimhgenetics.org/publications.
        As a retired biology teacher and foster/adoptive mother to 20 special needs kids I also have extensive training in human development and 40 years of practical experience in the field.
        You are correct that my grandmother was not an expert on epidemiology but she could teach you a few things about polite and effective communication.

        • 4ndy ledotter September 24, 2013 on 4:13 am

          Forgive me if I do not reach your standards of ‘polite’ after you propose eugenics by neglect, for it takes great willpower to offer any politeness. If you wish to decrease congenital disorders by genetic cleansing, then you could at least have the courage to shoot people in the head, rather than suggesting that they should die slowly and painfully of preventable diseases.
          Regardless, you have not actually addressed anything that I said. I am aware that ASD have genetic markers, but I note there the lack of any twins-separated-at-birth study. Without that, you cannot easily see the significance of environmental effects (whether epigenetic, neuroplastic or otherwise) in bringing about autism, and so risk making the oft-repeated fallacy of saying that a psychological condition ‘is genetic’ – akin to saying that a tropical plant is ‘defective’ because you can’t get it to grow in the Arctic circle. Given the exponential increase in cases of autism in the west, and that these conditions make people less likely to pass on their genes, there is a strong case that some aspects of our deteriorating culture are pivotal to this problem.
          I have seen first-hand as misinformed practices aggravated the conditions of fellow students with ASD back when I was in school, and I now fear for the safety of those 20 children in your custody.

          • ledotter 4ndy September 24, 2013 on 9:14 am

            4andy – you have been letting your over active imagination get the better of you. I have never mentioned ANY “solution” regarding modern society opting out of natural selection. If we are to have any discussion, polite or otherwise, you must refrain from projecting your conclusions onto my statements.
            That said, I do have hope for a solution. As one of those “educated people who refrained from having biological children” because of the risk of inflecting them with inheritable deleterious genes I would have given anything if I had been able to use IVF to screen egg and sperm for the familial genetic defect. Or to know that there was a gene therapy available to correct it either in utero or after birth. These procedures are becoming reality so there is no need to even discuss letting anyone die a painful death. However, if these new screening techniques and gene therapies are halted by the religious wing nuts
            we will continue to see children born who will suffer long and painful LIFE!
            As for my 20 kids – 19 have grown up and are successfully functioning as independent adults. Even my adopted daughter who was never supposed to walk or talk! And you, sir, know nothing about “painful” death until you have loved and cared for a severely disabled child for years only to hold her as she died due to medical incompetence!

  • Zovits Ádám September 19, 2013 on 1:35 am

    So in places where there is less sanitation there are less people with Alzheimer’s? Couldn’t it be because those born with the disease die earlier due to the local lack of sanitation?
    OTOH, I too think that we in the west live in an oversterilized environment.

    • 4ndy Zovits Ádám September 22, 2013 on 11:01 am

      “Then they compared those countries’ rates of Alzheimer’s disease with those of developed countries, *adjusting for life expectancy*. They found that differences in levels of sanitation, infectious disease and urbanization accounted statistically for about a third of the discrepancy in Alzheimer’s rates between countries.”

  • ledotter September 19, 2013 on 6:00 am

    Would the moderator care to comment on the reasons for not posting my comment?

    • ledotter ledotter September 19, 2013 on 6:01 am

      OK it showed up – it was my server having problems.

  • Roger Newcomb September 20, 2013 on 1:50 pm

    “For example, rates of Alzheimer’s disease are higher in developed nations — a fact that is often attributed to the longer life expectancies in those countries. But the higher rates persist even after correcting for longer lifespans, according to a recent study led by Cambridge evolutionary biologist Molly Fox.”

    Again, the ever-present question: correlation vs. causation.

    In the developed nations we literally live in a sea of unnatural chemicals, and some of the chemicals we use to sanitize our bodies and living environments get into our bodies where the effects may be unknown. Is this the primary factor in the causation of Alzheimer’s?

    Have the researchers looked at isolated rural environments where there a few such contaminants and where the residents are long-lived? I wonder what they would find……..

    • Cameron Scott Roger Newcomb September 23, 2013 on 8:37 pm

      That’s an interesting question. A deep dive into the study’s methodology might begin to address it, and there certainly have been efforts to link all kinds of substances to Alzheimer’s. But the chemicals we use every day are largely untested, unless they fall into some very specific areas of scrutiny like pesticides and medications.

  • Grim September 21, 2013 on 7:58 am

    A few article’s studies looking at putting the alzhiemer’s on copper.
    The lead pipes of the future =P