WEEK 9 - "Epidemiologists prefer causal relationships."

The Mediterranean diet is based on epidemiological (population) studies.  The Nurse's Health Study is a longitudinal study looking at causal relationships between behavior and health.  And currently, there are many more studies at Tufts investigating populations such as the Baltimore Study on Aging and the Jackson Heart Study.  Nutritional epidemiology and chronic disease epidemiology have been studied for decades and help form hypotheses that mold our understanding of health and wellness.  But, I caution people not to take the results from such studies as Gospel truth.  In my classes, I make light of drawing too strong a conclusion when looking at epidemiological data alone.  For example, in my Fundamentals of Nutrition course, I challenge students' thinking by starting with the following question: Do all "population trends" have a cause and effect relationship?  

For the most part, the class can agree that the answer should be "no".  Although there is a correlation, there may not be causation.  I go on to joke about heart disease as it is correlated to fat and alcohol consumption.  Comparatively:

• Japanese eat less fat and suffer fewer heart attacks than British or Americans.
• French eat a higher % of fat and suffer fewer heart attacks than British or Americans.
• Japanese drink less red wine but suffer fewer heart attacks than British or Americans. 
• French drink more red wine but suffer fewer heart attacks than British or Americans.
• Germans drink more beer, eat more high fat sausages and suffer fewer heart attacks than British or Americans.

If we were basing a conclusion on correlation alone, the conclusion could be: We can eat as much fat and drink alcohol as much or little as we like; it is speaking English that is apparently linked to heart disease.

 But, I also want to state that I believe that there is great value in epidemiological studies setting the foundation of further research and investigation or as a means for us to draw conclusions about a specific population under a specific set of circumstances.  It is an amazing first step to scientific discovery.  It is the basis for much of the nutrition and exercise physiology research today.  Scientists start by observing trends in populations.  The scientists then write grants to ask for funding.  If the grant is approved, the scientific researcher will design a study to look at a cause and effect relationship.  The more research is done on a topic, the more the body of evidence grows to support the hypothesis.  

This past week, I was fortunate enough to work with research teams and firefighters at the University of Illinois investigating cognition before and after a blaze (extreme physical exertion, heat stress, etc.).  The firefighters at the Illinois Fire Service Institute were chosen for this research as the results apply directly to their population as a whole.  It is of utmost importance that rapid and accurate decisions are made when fighting a fire....lives depend on it!  I watched as the subjects conducted several cognitive tasks prior to the blaze.

 Once they completed the pre-testing, they got in their gear, completed an hour long drill involving putting out a three story fire while saving the lives of dummies, and then returned to the classroom for cognitive post-testing.  The firefighters were spent.  Several men had to stop while returning to the classroom to vomit or heave.  Beads of sweat dripped off of their face and they looked like a horse that was rode hard and put away wet.  In short, they were exhausted.  

I continued the conversation with the researchers about their current research design, what they wanted to do with the findings of this study and more.  But, most interestingly to me was my reflection of the tangental conversation that resulted while we watched the building burn and the firefighters extinguish the blase.  We began to discuss the alarming rate of heart attacks among firefighters who are in the line of duty.   According to an article published in Cardiology in Review, "Cardiovascular disease is the leading cause of on-duty death among firefighters (45% of on-duty fatalities) and a major cause of morbidity."  Surprisingly, heart attacks kill more firefighters on duty than fires!  The researchers and I went on to discuss chronic disease and how it is not diet alone, exercise alone, or a lack of stress that decrease your chances of suffering from a chronic disease like heart disease...but, you need pay attention to this trifecta and make positive life choices on all three fronts to decrease your chances of cardiovascular disease.  

It fascinates me to look at the path this sabbatical has taken me and the lessons I have learned.  They are all causing me great pause and each new experience I encounter can be shared with a lesson.