IU math professor uncovers flaws in highly publicized ‘obesity is contagious’ study.
by Medical Xpress:
In their original paper, Nicholas Christakis of Harvard and James Fowler of the University of California, San Diego claimed to have provided evidence of a “three-degrees-of-influence rule of social contagion” within networks such as families and friend groups where obesity characteristics could be transmitted socially. They went on to include other personal characteristics — divorce, smoking and even loneliness — in their social contagion theory, and their research took off in the media, accompanied by publication of their 2009 book “Connected” and appearances on the shows “Good Morning America” and “The Colbert Report.” Christakis built on his research to form a company, MedNetworks, which proposes to help pharmaceutical companies get doctors to prescribe more of their drugs.
When Lyons reviewed the evidence, he found not only a lack of statistical significance in the findings, but also that both the researchers and the reviewers did not realize that the statistical procedures Christakis and Fowler had used were inapplicable. Their methods, Lyons found, were fundamentally flawed.
Lyons is not arguing that social contagion, or peer pressure, doesn’t exist: He agrees that people influence each other. Rather, Lyons shows that the research did not support the paper’s contention that one could measure how much people influence one another, whether the people are one, two or three steps out in the network of family or friends.
“The problem is that their methods were deeply flawed from bottom to top: The models used to analyze the sparse data contradict the data and the conclusions, and the method used to estimate the dubious models does not apply,” he said. “The statistical significance tests that were applied to the questionable estimates do not show the differences they have proposed.”
In the past 90 days, The New York Times , The Boston Globe , Slate and the Irish Medical Times , among numerous other media, have written about Lyons’ critique. The Strategy Research Initiative, a group that includes scholars from Harvard, Duke, Dartmouth, Columbia and Yale, now lists Lyons’ research as an “Exemplary Paper” in the area of Theoretical Critiques of Empirical Work.
Among those who have since joined Lyons in questioning the results are Columbia University professor of statistics Andrew Gelman and Oxford University professor of statistics in social sciences Tom Snijders. Other critiques have come from Hans Noel, Georgetown University, and Brendan Nyhan, Dartmouth, and from Carnegie Mellon University statistics professors Cosma Shalizi and Andrew Thomas.
“I tried to get high-profile journals interested in my critique, telling them about the wide interest the topic had, but to no avail,” he recalled. “I don’t think I got any special treatment; these were simply their policies. In fact, that’s one of my main points: From flawed statistics in research to poor-quality review to difficulty in publishing critiques, this is all too common. And that’s why I think these are important points, ones that I emphasize to my students when I teach statistics. They need to be wary.”
Plain and simple, correlation is not causation.
It should be noted that the obesity researchers are/were working with pharmaceutical companies in increasing weight loss dosage for individuals.