PERSONAL VIEW - PDF document

24 8 November 2014 | the bmj PERSONAL VIEW The “hygiene hypothesis” for allergic disease is a misnomer “Biome depletion” is a better term for how immune function is undermined in industrialised societies, writes William Parker , 25 years after The BMJ published David Strachan’s seminal hypothesis A publication by David Strachan in The BMJ in  described the idea that a loss of species diversity from the ecosystem of the human body could lead to allergic disease ( BMJ ; :-).  Subsequent studies have focused on exactly which species of symbionts might be important,  and they have expanded the model beyond allergy to include autoim - mune diseases  and cognitive disorders related to inammation.  This view, now conrmed by a vast body of literature as a cornerstone of immu - nology, is likely to aect the discipline of cancer study in the future.  Strachan’s view can be accurately described as “biome depletion,” an evolutionary mismatch that works in tandem with other mismatches (for example, inammatory diets and vitamin D deciency) to undermine immune function in industrialised societies.  Strachan articulated his quantum leap of thinking in his  paper, stating, “These observations do not support sug - gestions that viral infections, particularly of the respiratory tract, are important precipitants of the expression of atopy. They could, however, be explained if allergic diseases were prevented by infection in early childhood.” prevailing notion that immune diseases, par - ticularly asthma, were the results of infections. Instead, he suggested the seemingly bizarre notion—now widely appreciated—that coloni - sation by an organism could prevent an allergic disease that was apparently unrelated to that organism. Strachan’s view eventually became associated with the nickname “the hygiene hypothesis,” a term that had already been coined: David Barker used the term more than once in  to explain an increasing incidence of appendicitis.   Barker’s hygiene hypothesis used the considerably older, and now disproved, view that hygiene led to a delayed exposure to infectious agents and that it was the exposure to those infectious agents rela - tively late in life that caused immune disease.   So, Strachan’s advance was not the already long held view that hygiene was a problem; rather, he identied a loss of species diversity from the ecosystem of the human body as a prob - lem. With this in mind, it seems appropriate to label Strachan’s advance with a name other than “the hygiene hypothesis.” And the reasons for being careful about this label extend beyond the correct attribution of the term to its originator. First and foremost, the term “hygiene hypo- thesis” has become a misnomer. Biome depletion in Western culture was indeed induced in the th century by the revolutionary and widespread use of such technological advances as sewer systems and water treatment facilities. However, hygiene today is associated much more with handwash - ing and the use of a dust mop than the availability of a toilet and clean drink - ing water. This modern view of hygiene—relating to personal health habits rather than advancing technology—is not a signi - cant factor in the increased incidence of allergic disease. On the contrary, a lack of handwashing oen results in an increased incidence of u and other acute infections, many of which exacerbate rather than mitigate allergy and autoimmunity. Furthermore, modern hygienic practices oen alleviate, not increase, allergy—by reducing the levels of allergens produced by organisms such as dust mites, cockroaches, and mould. Thus, aller - gies and autoimmune diseases are not caused by “hygiene” as people now think of it. Issues regarding the inaccuracy of the term “hygiene hypothesis” are compounded because the biome depletion paradigm forms a fundamental principle of modern immu - nology and can no longer be considered a hypothesis. So, not only is the underlying cause of allergy and autoimmunity unrelated to hygiene as we understand it today, but our understanding of the cause ceased to be a hypothesis some years ago. More important than issues of attribution or inaccuracy, use of the term “hygiene hypothesis” in connection with dreaded immune diseases gives credence to the view that hygiene is not benecial— potentially undermining public health eorts aimed at avoiding the spread of infectious dis - ease. Perhaps most importantly, the term diverts attention from the intuitive solution to the prob - lem of biome depletion: biome enrichment or restoration.  Barker’s term “hygiene hypothesis,” which he applied to a view much older than his own work, clearly deserves its place in the history books as part of our ongoing evolution in understand - ing the pandemics of non-infectious, immune related diseases that plague industrialised soci - eties. But the term is a complete misnomer that can deect attention from potential solutions. It is time to provide the model with an appro - priate and productive name, giving credit not only to Strachan, but also to those who have expanded the view of the model over the years to include depletion of organisms that do not nec - essarily cause disease, as well as a wide range of autoimmune and cognitive diseases related to immune dysfunction. William Parker is associate professor, Department of Surgery, Duke University Medical Center, Box , Durham, NC , USA William.Parker@duke.edu I thank Chantal Villeneuve of Tus University (Veterinary Medicine), Somerville, Massachusetts, USA; and Randal R Bollinger, Duke University Medical Center (Surgery), Durham, North Carolina, USA. Competing interests : None declared. Provenance and peer review : Not commissioned; externally peer reviewed. References are in the version on thebmj.com. Cite this as: BMJ ;:g Modern hygienic practices often alleviate, not increase, allergy—by reducing the levels of allergens produced by organisms such as dust mites, cockroaches, and mould   Read rapid responses to this article at bit.ly/hygieneresponse Enriching his biome PB 8 November 2014 | the bmj the bmj | 8 November 2014 39 Who are you, what do you need, and how do I figu

re out how to care for you? Fundamentally, those are the questions that drive every encounter between a doctor and a patient. A recent article in the New England Journal of Medicine calls for us to expand the “social history” facet of this to include six domains: individual characteristics, life circumstances, emotional health, perceptions of healthcare, health related behaviours, and access to and utilisation of health. The authors acknowledge that in primary care such comprehensive information may be “best obtained over multiple visits,” which is possible in a long term continuous relationship, but this still presents the challenge of how best to gather the history and what to do with it. In gathering a social history, it is important to consider whether the primary issue at hand is the information that is gathered (eg, documentation of resuscitation preferences, tobacco use, or marital status), or the conversation and relationship building. Sometimes, even the most thorough gathering of social history leads to the same amount of essentially flat and affectless note taking as reviewing a medication list. This can lead to both missing the patient’s story, and focusing on what has already happened at the expense of what could be done about it. To illustrate: when I discuss smoking, to an extent I don’t care exactly how many packs my patient has smoked, I want to talk about how we can make it less. Rather than focusing on quantifying the history, I want to engage in a discussion of whether there have been or are likely to be consequences, and how we can work on cutting back. On the other hand, sometimes documentation of the social stuff is important (again, resuscitation wishes, etc). And we need to be clear in our own heads when the “social history” conversation is about documentation, and when it is relational or therapeutic, as they are different types of conversation. The other side of this, however, is the issue of time. This is not just “patient time” versus “paperwork (or computer) time,” or the oft heard complaints about being expected to “produce” too much clinical volume to be able to give good clinical primary care. This is about “patient time” versus “patient time.” I’ve had several visits recently with patients who love to chat—and that’s great—and from at least one of those chats I learned the extent to which the patient’s primary health concern was really about the health of another family member. Yet we are in the profession of caring for the sick, and the sick person who I see  minutes late, because of wonderful conversations with other patients, does not care how wonderful those conversations were. Understanding social context is fundamental to understanding our patients, and we want to provide thoroughly compassionate care, but we care for a population, which means that sometimes relational work with one patient may have to be sacrificed to attend to care for another. Thoroughness, care for all our patients, and timeliness: all are important, but it is nearly impossible to meet all three goals all of the time. LAST WORDS   @mgtmccartney BMJ BLOG OF THE WEEK William E Cayley Jr Patient time v patient time children had misused drugs or alcohol; a third had mental health problems Under my fingertips, indentations from a now obsolete typewriter flit like Braille. Medicine’s recent past was typed or written by hand. Flicking through these fading paper records like a book, one of my jobs is to summarise them onto a computer. And sometimes there is a pattern. Shortly aer birth the baby is crying a lot, teething, unhappy. Something illegible is prescribed from the end of a fountain pen. A couple of years later, a broken bone. Someone tells the doctor that the child is behaving badly. DNAs—“did not attends”— actually mean “child not brought by the adults responsible.” Vaccination schedules slip. Frequent presentations occur with one word outcomes. The copperplate swirls make no other comment. A head injury; another accident. A presentation to the emergency department with intoxication in late childhood. And then silence, which is later broken by anxiety, depression, or obsessional thoughts in the late teens and early s. Consultations are then frequent— some in the emergency department, some with the out-of-hours service. A letter from the drugs and alcohol service, or a psychiatric nurse, aer an intentional overdose. This may recur oen. The patient may leave before a full assessment and then not be seen until the next crisis. Self harm is rife. And aer that comes the devastation of sexual abuse in childhood. Some  cases of child sex abuse went unchecked in Rotherham from  to , the horrendous recent report details.  Half of these alcohol; a third had mental health problems; two thirds had emotional diculties. Almost half came from a home with reports of domestic abuse, and two thirds had refused to go to school or been repeatedly reported as missing from home. This was against a backdrop of underfunded social and care services, impossibly long waiting lists for counselling, and children afraid to give evidence against their abusers. GPs are pattern spotters—but not every such pattern indicates a child at risk. Electronic records disjoint patients’ narratives across separate documents, each a click away. Might this make patterns harder to spot? Either way, as GPs we need named social workers in our teams who we can talk to as regularly as our health visitors. And we need to fund health and social services properly, so that the most vulnerable children always get the priority they need. Margaret McCartney is a GP, Glasgow margaret@margaretmccartney.com Competing interests and references are in the version on thebmj.com . Cite this as: BMJ ;:g NO HOLDS BARRED Margaret McCartney Pattern spotting The sick person I see 20 minutes late, because of wonderful conversations with other patients, does not care how wonderful those conversations were William E Cayley Jr practises at the Augusta Family Medicine Clinic; teaches at the Eau Claire Family Medicine Residency; and is a professor at the University of Wisconsin, Department of Family Medicine  Read this blog in full and other blogs at thebmj.com/blogs   Baby P: The Untold Story , reviewed ( BMJ ; :g)