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Culinary Metaphor Used To Understand Gene-Environment Interactions

a pie cut in almost half with the smaller piece labeled Environmental and the larger piece labeled GeneticA recent article in the Archives of General Psychiatry by Hallmayer et al. discussed the role of genetic and environmental factors in autism and autism spectrum disorders (ASD).  The study was a heritability analysis of 192 pairs of twins, which attributed 37 percent of the variation in risk of autism to genetic factors and 55 percent to shared environmental factors.  The authors contrasted their findings with those of previous studies, which had given genetics a much higher share (up to 90%).

Rather than contradicting previous research, the new results provide more evidence that autism, like many other common diseases, results from both genetic and environmental factors.  The way that these elements – often called “nature and nurture” – influence health outcomes has been discussed for decades but is often misunderstood, even among scientists.

Disease Causation is Not as Easy as… Pie

Heritability analysis focuses on sources of variation in specific populations.  A common misinterpretation of these types of analyses is that the causes of a particular disease are cleanly, though errantly, summed up as slices of a pie – or in pie chart fashion.  For example, it is not uncommon to have the explanation of disease presented as “25 percent genetic and 75 percent environmental,” adding up to 100 percent of cases.  Furthermore, from the perspective of “either/or,” a person with gene variant “X” is thought to be destined to develop colon cancer no matter what his diet, whereas a person with gene variant “Y” can smoke all she wants yet will never develop lung cancer, and so on. However, what we have learned from gene-disease association studies is that, in reality, human disease is rarely a product of such simple and clearly defined relationships.  Causation of human disease is not about nature OR nurture but more about nature AND nurture.

Disease Outcomes “Stew”

several pots and pans over flames with different vegetables tossed into them

Most common diseases–such as coronary heart disease, cancer, and diabetes, which affect millions of Americans–are caused by modifiable environmental risk factors such as cigarette smoking, diet, and sedentary lifestyle.  Because gene-environment interactions underlie almost all human diseases, a large role for the environment does not preclude an equally large role for genetic factors. Interaction among genetic and environmental factors allows the total contribution of individual risk factors to exceed 100%.

Rather than slices of pie, perhaps we should consider another metaphor from the culinary world: vegetable stew – in which genes are represented by the many different ingredients and the environment by the time length and temperature of the cooking and whether the pot or pan used is constructed of cast iron, earthenware, or steel.  Every skilled chef knows that any change in the preparation of stew, soup or similar entree can result in a completely different taste.  Each cut of vegetable: carrot, tomato, onion, potato, mushroom, celery, etc and every spice could be of a different variety.  Once assembled, the ingredients blend and cook together to produce a combined yet completely unique flavor.  Biologic processes function in a similar way, as genes respond to a continually varying environment over time to produce various health outcomes.A hourglass filled with different genetic and environmental factors on a fire

Even though we may know many ways to prevent common disease through the manipulation of environmental factors, one important reason to study and understand genetic factors is that our current public health approaches to prevention have not been entirely successful.  Most people do not get enough physical activity or eat a healthy diet. Many are obese or overweight, and many do not adhere to public health screening recommendations. Genetic research may help us better understand disease risks and target our environmental interventions to people who need them the most in order to best achieve public health goals with scarce resources.

Keep in mind that, in spite of having mapped the sequence of the human genome, scientists do not yet have the tools to quantify or even guess at the vast array of gene-environment interactions important to human health. In general, genetic tests that are developed and marketed to the public for predicting risk of common diseases do not account for environmental risk factors, much less for gene-environment interactions.  Not surprisingly, these tests tend to have little predictive value {CDC Podcast on Personal Genomic Tests}.  Genes do not define one’s destiny and public health messages which pertain to daily life decisions are as relevant today as ever before: eat a healthy diet, exercise, and don’t smoke.

*This blog post was originally published at Genomics and Health Impact Blog*


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Richmond, VA – In an effort to simplify inpatient medical billing, one area hospitalist group has determined that “altered mental status” (ICD-9 780.97) is the most efficient code for use in any patient work up.

“When you enter a hospital, you’re bound to have some kind of mental status change,” said Dr. Fishbinder, co-partner of Area Hospitalists, PLLC. “Whether it’s confusion about where your room is located in relationship to the visitor’s parking structure, frustration with being woken up every hour or two to check your vital signs, or just plain old fatigue from being sick, you are not thinking as clearly as before you were admitted. And that’s all the justification we need to order anything from drug and toxin screens, to blood cultures, brain MRIs, tagged red blood cell nuclear scans, or cardiac Holter monitoring. There really is no limit to what we can pursue with our tests.”

Common causes of mental status changes in the elderly include medicine-induced cognitive side effects, disorientation due to disruption in daily routines, age-related memory impairment, and urinary tract infections.

“The urinalysis is not a very exciting medical test,” stated Dr. Fishbinder. “It doesn’t matter that it’s cheap, fast, and most likely to provide an explanation for strange behavior in hospitalized patients. It’s really not as elegant as the testing involved in a chronic anemia or metabolic encephalopathy work up. I keep it in my back pocket in case all other tests are negative, including brain MRIs and PET scans.”

Nursing staff at Richmond Medical Hospital report that efforts to inform hospitalists about foul smelling urine have generally fallen on deaf ears. “I have tried to tell the hospitalists about cloudy or bloody urine that I see in patients who are undergoing extensive work ups for mental status changes,” reports nurse Sandy Anderson. “But they insist that ‘all urine smells bad’ and it’s really more of a red herring.”

Another nurse reports that delay in diagnosing urinary tract infections (while patients are scheduled for brain MRIs, nuclear scans, and biopsies) can lead to worsening symptoms which accelerate and expand testing. “Some of my patients are transferred to the ICU during the altered mental status work up,” states nurse Anita Misra. “The doctors seem to be very excited about the additional technology available to them in the intensive care setting. Between the central line placement, arterial blood gasses, and vast array of IV fluid and medication options, urosepsis is really an excellent entré into a whole new level of care.”

“As far as medicine-induced mental status changes are concerned,” added Dr. Fishbinder, “We’ve never seen a single case in the past 10 years. Today’s patients are incredibly resilient and can tolerate mixes of opioids, anti-depressants, anti-histamines, and benzodiazepines without any difficulty. We know this because most patients have been prescribed these cocktails and have been taking them for years.”

Patient family members have expressed gratitude for Dr. Fishbinder’s diagnostic process, and report that they are very pleased that he is doing everything in his power to “get to the bottom” of why their loved one isn’t as sharp as they used to be.

“I thought my mom was acting strange ever since she started taking stronger pain medicine for her arthritis,” says Nelly Hurtong, the daughter of one of Dr. Fishbinder’s inpatients. “But now I see that there are deeper reasons for her ‘altered mental status’ thanks to the brain MRI that showed some mild generalized atrophy.”

Hospital administrators praise Dr. Fishbinder as one of their top physicians. “He will do whatever it takes to figure out the true cause of patients’ cognitive impairments.” Says CEO, Daniel Griffiths. “And not only is that good medicine, it is great for our Press Ganey scores and our bottom line.”

As for the nursing staff, Griffiths offered a less glowing review. “It’s unfortunate that our nurses seem preoccupied with urine testing and medication reconciliation. I think it might be time for us to mandate further training to help them appreciate more of the medical nuances inherent in quality patient care.”

Dr. Fishbinder is in the process of creating a half-day seminar on ‘altered mental status in the inpatient setting,’ offering CME credits to physicians who enroll. Richmond Medical Hospital intends to sponsor Dr. Fishbinder’s course, and franchise it to other hospitals in the state, and ultimately nationally.

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