Saturday, 16 May 2009

• The spurious confounder

  My brain is in one of those "not able to process fast enough" modes at the moment (4:36 a.m. Pacific). Three articles are rattling around in my brain, running into my experience and training and lots of other stuff in there (hi, elementary school tormentors, how are you doing, jerks?!?).
  
  Deep breath.
  
  Doesn't "spurious confounder" sound like a phrase that ideally would be accompanied by "dangnabit!"
  
  The spurious confounder in question? BMI.
  
  I have often thought that it might be just such a critter. And I have agreement coming at me in the form of an article linked from Shapely Prose in [interruption for awake superheroprincess calling me -- okay back now, 9 a.m., better chance to be coherent] this post by Fillyjonk on The Nocebo Effect. Commenter Vixen pointed to a fascinating article on BioMed Central Public Health by Peter Muennig, Ph.D., MPH, Department of Health Policy and Management, Mailman School of Public Health, Columbia University, New York. In article, called "The body politic: the relationship between stigma and obesity-associated disease," Muennig lays out four hypotheses for how "the stress associated with social stigma and negative body image among obese persons explains some of the weight-associated morbidity that researchers had previous attributed to adiposity alone."
  
  [Okay, based on that line alone, I'm ready to add Peter Muennig to my collectable set of my favorite "thinkers on obesity" trading cards. A few of the many guests at my version of Judy Chicago's The Dinner Party would include Katherine M. Flegal, Linda Bacon, Paul Campos, Gina Kolata and now, Peter Muennig.]
  
  Addressing one of his hypotheses, Muennig states, "Consider that it is weight dissatisfaction that is driving the relationship between BMI and health, and that BMI is a spurious confounder." He designed a study to look at the difference between a respondent's desired or "ideal" weight and their reported weight, and then looked at the differences in days a person felt ill between those who had big gaps between ideal and reported weight, and those who did not. The study looked at responses to the Behavioral Risk Factor Surveillance Survey, a telephone survey conducted annually, and one of the bread-and-butter sources of U.S. health surveillance. (The BRFSS has many limitations, but I won't go into them here). What the study, covered in more detail in this article in the American Journal of Public Health by the same lead author, found is that the "difference between actual and desired body weight was a stronger predictor than was body mass index (BMI) of mental and physical health." This study found that in some statistical models, "a higher BMI is predictive of fewer unhealthy days than a lower BMI once the relative desire to lose weight is controlled for."
  Yep.
  And, then there's this:
  

  If a distorted body image leads to stress and thus morbidity, we would expect that young males who see themselves as too skinny would also suffer. In post-publication analyses, Rufina Lee and Marilyn Sinkowitz of Columbia University, explored whether the desire to gain weight also predicted greater physical and mental unhealthy days among young males. Here, too, a measure of distorted body image – in this case, the desire to gain weight – was correlated with psychological and physiological morbidity among males aged 18 to 30 (unpublished results).
  

  That's right, it's worth repeating: for young guys, seeing onself as too skinny was also correlated with psychological and physiological morbidity.
  
  From Muennig's conclusion, there is this gem:
  

  It is important to understand the role that stigma plays in producing disease amongst overweight and obese persons for many reasons. Foremost, the assumptions surrounding the pathophysiology of overweight and obesity could be partially incorrect. Second, if stigma-induced stress plays a role in the pathophysiology of obesity, it suggests that social constructs of idealized body image can have harmful health effects. If so, it raises pragmatic questions surrounding the net health benefits of public health communications campaigns, which often promote thinness.
  

  
  I am excited to read this (I know, I'm such a public health geek) talk about the "net health benefits of public health communications campaigns." I'm thinking, how can I get President Obama to read this article? Especially with Thomas Frieden as new head of the CDC (I'm actually waiting and seeing on this, because there's almost no way he'll be more damaging to public health than the previous CDC director).
  
  So, to article two (sorry it has taken so long for me to get here), the original article that Fillyjonk linked to from The New Scientist, their cover story on "How Beliefs Can Harm You" -- with the headline inside of "The Science of Voodoo: When mind attacks body".
  
  The quote from that article that stood out to me was this one: "One study found that women who believed they are particularly prone to heart attack are nearly four times as likely to die from coronary conditions than other women with the same risk factors." So, when we public health types are telling people that having a particular condition makes you more likely to get ill or die from illness, what impact is that having on health? Wouldn't it be better to use the placebo effect than the nocebo effect to encourage people to think of themselves in good health?
  
  So, here's where it gets personal. This week, I saw both PhD Coachy and, for the first time since the beginning of the year (and since the miscarriage), Doc Thoughtful (my primary care doc). PhD Coachy has been recommending that I read (knowing my critical eye) "Feeling Good" by David Burns (or the "Feeling Good Workbook," depending on which one resonates more with me) and the concept that there are thoughts I'm thinking that I could address with more rational thought, and that this in turn can have an impact on mood and actions, well, it all makes sense and connects up well with the "beliefs can harm you" stuff above. I'm not advocating this book or approach for everyone, and seeing how poorly I was feeling emotionally over the past few weeks, I did have a conversation with Doc Thoughtful about potentially starting an antidepressant. But, sitting there in Doc Thoughtful's office, wiping some tears from my eyes as he asked how I was doing after the miscarriage, he asked me other questions. We went over my lab results, which were really good, my A1C was 5.7%, which is really good, and if I were an objective observer, I would have noticed it wasn't Doc Thoughtful raising concerns about weight, or telling me to do anything differently. He wasn't telling me to exercise more, eat less or differently (although we both agreed I would start taking my statin again to lower my LDL, which wasn't high but higher than ideal for a person with diabetes). We talked about which antidepressant I would take if I decided I wanted to take one. The one comment that he made that was a little cringe-worthy was when I mentioned the dance stuff I've been doing and he made some mention of "burning calories" (which made sense, given how much I had focused on weight during the visit), but I said, no, it was more for the mood-lifting and stress-reducing benefits, which led us to an interesting discussion about dance. So I left, without a prescription for antidepressants but knowing I could get one, with the knowledge that my blood pressure, blood sugar and blood lipids were in or near the ideal range. And, immediately prior to this visit, I actually did my first annual mammogram (I had done one before to rule out some worrisome lumpiness a few years back, so this wasn't my first one). It didn't hurt, and was maybe just a tiny bit uncomfortable for a few seconds. I ought to have felt proud of taking good care of my health.
  
  Yet, I didn't feel healthy.
  
  Especially when I returned to my work, which sometimes is about promoting awareness of health risks. Sometimes it's not about that, and often it's very positive. But what does the work I do to "raise awareness" do to people who feel healthy, and then are told that they are "at risk." I'll have to think about this more before I answer. I'm generally very, very tuned into the "harm/benefit balance" -- I know that this worrying that I do is prized by the people I work for and with because I'm tuned into things that they sometimes are not.
  
  So, now to the third article, this one from Maclean's (Canada's newsweekly magazine) called "Size Isn't Everything." Here's one quote:
  

  “We need to stop saying, ‘Everyone with a BMI over 25 needs to lose weight,’ ” says Christina Sherry, a nutritional science research fellow at the University of Illinois. “If you’re trying to lose 20 lb., that stress in itself can cause more [health] complications than the weight you’re trying to lose.”
  

  The article overall isn't necessarily fat-positive, but here's a statement I found intersting, "There’s one point, though, that’s impossible to argue: heavy people who improve their lifestyle are almost certainly better off, even if they never drop a pound." This doesn't address the idea that "heavy people" who are not stigmatized are also "almost certainly better off, even if they never drop a pound." Another study is cited in the article which "showed a marked improvement in risk factors for diabetes and cardiovascular disease, suggesting that losing visceral fat, not achieving a “healthy weight,” should be the clinical goal." As far as clinical goals go, that is an improvement. I got to the article from Dr. Arya Sharma's blog, as his "Edmonton Obesity Staging System" is mentioned (and he is quoted). I'm a little less in like with Dr. Sharma these days (strangely, he doesn't consult with me before forming his opinions), but I'm glad his views are getting play.
  
  So, to end this very, very long post (if you've read this far, you're nearly there!), I'll go back to the personal. I am trying on Dr. David Burns' advice -- I will focus on doing what I can to control my thoughts. To that end, here's what I'm focusing on:
  I am healthy
  I am strong
  I am caring
  I am attractive
  
  What conclusions are you drawing, from political to personal, from all of this?
  

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