Experts React to CDC Admission That Study Overstated Number of Obesity-Related Deaths
Several government and public health experts on Tuesday responded to an internal CDC investigation that determined a widely quoted agency study on obesity that was published in the Journal of the American Medical Association inflated the number of deaths related to obesity by tens of thousands because of statistical errors, USA Today reports. The report also said that obesity is gaining rapidly on tobacco as the leading cause of preventable death.
Dixie Snider, CDC's chief of science and the official leading the internal inquiry into the study, said, "We regret the unintentional error and any confusion it may have caused, but we stand by the bottom line message: Tobacco and obesity are the two major risk factors for preventable death in the United States" (Hellmich, USA Today, 11/24). Snider said the agency plans to reduce its estimated death total by a yet-to-be-determined number. He added that the new results would still show an increase in obesity-related deaths over the 300,000 estimated in 1990. The correction would not change obesity's ranking as the second-leading cause of preventable death in the nation. Snider said that CDC will submit an erratum or correction to JAMA (California Healthline, 11/23).
He added that while CDC has submitted corrections to major scientific journals in the past, the obesity study "unfortunately ... was a paper that received a lot of attention and had our director's name on it. To my knowledge that confluence of events really hasn't occurred at the same time" (Yee, AP/Long Island Newsday, 11/23). Phil Fontanarosa, executive editor of JAMA, said he could not comment on the pending CDC correction but added that the study had been reviewed by experts prior to publication (McKenna, Atlanta Journal-Constitution, 11/24).
Stanton Glantz, a professor of medicine and director of the Center for Tobacco Control Research and Education at the University of California-San Francisco, said, "The kind of policies one would develop for something that is killing about as many people as tobacco or a quarter as many people as tobacco are very different." Eric Oliver, a political scientist at the University of Chicago, added, "The numbers simply don't add up" (Kolata, New York Times, 11/24). Dan Mindus, an analyst for the Center for Consumer Freedom, said CDC's admission of error "is a good start," adding, "A full investigation into the obesity death tally will reveal multiple flaws that seriously overstate the obesity problem and is leading to knee-jerk policymaking and litigation" (Stein, Washington Post, 11/24).
However, Louis Aronne, president of the North American Association for the Study of Obesity, said whether obesity surpasses tobacco as the leading cause of preventable deaths "this year or next year or 10 years from now, the point is clear: It's a serious health problem in the United States." George Blackburn of Harvard Medical School added, "Obesity is one of the most daunting health challenges of the 21st century. Focusing on this one number is silly" (USA Today, 11/24).
The CDC study in question was based on U.S. mortality data for 2000. Ali Mokdad, chief of the behavioral surveillance branch at CDC, and colleagues reviewed studies on the role that lifestyle factors have in the development of such conditions as diabetes or stroke to estimate how many of the deaths could be attributed to lifestyle. They also compared their data with a similar study conducted using 1990 U.S. mortality data. Researchers found that an estimated 400,000 people died from causes related to poor eating habits and sedentary lifestyles -- 33% more than in 1990, when obesity was a factor in 300,000 deaths. In comparison, 435,000 people died from smoking or exposure to tobacco in 2000, up from 400,000 in 1990.
Tobacco's share as the cause of total U.S. deaths between 1990 and 2000 dropped from 19% to 18.1%. Researchers found that 16.6% of 2000's preventable deaths could be attributed to poor diet and physical inactivity, up from 14% in 1990. According to the study, obesity would become the leading cause of death by next year, surpassing 500,000 deaths annually to rival the number of deaths each year from cancer. The study led to an HHS ad campaign on obesity and an increased focus on obesity in research at NIH, which increased its obesity research funding from $378.6 million in 2003 to $400.1 million in 2004.
The CDC's internal review of the study identified that certain mathematical mistakes, such as using a total mortality number from the wrong year, might have incorrectly added 80,000 to the total estimated 400,000 obesity-related deaths. Such a mistake could have increased the growth rate of obesity mortality by 23 percentage points. The Institute of Medicine -- at the request of CDC -- in December will hold a two-day workshop on how to factor in risky behaviors in determining mortality causes. The Wall Street Journal on Tuesday reported that two CDC researchers completed papers prior to the report's release stating that the traditional method for calculating obesity-related deaths -- which the study's authors used -- is flawed because it does not properly take into account such factors as age and smoking.
CDC Director Julie Gerberding said that warnings from dissenting CDC scientists had not been properly heeded and that the internal review panel has recommended that the agency modify its review process to better address concerns. Rep. Henry Waxman (D-Calif.) also has asked the Government Accountability Office to conduct its own investigation, which is pending until after CDC releases the results of its internal review (California Healthline, 11/23).