'Obesity paradox' not found when measuring new cases of cardiovascular disease

December 7, 2017, New York University
Credit: CC0 Public Domain

Although obesity is a well-known risk factor for getting cardiovascular disease, a controversial body of research suggests that obesity may actually be associated with improved survival among people who have cardiovascular disease.

However, a new study by NYU College of Global Public Health and the University of Michigan finds that this " paradox" is not present among people with new cases of . Most prior work examines people with more longstanding disease, where disease-related factors can bias findings towards the observation of a paradox.

"Given that many diseases result in wasting at the end of life, the notion that extra catabolic reserve can prolong survival makes intuitive sense. There are also explanations relating to a various inflammatory and neurohormonal processes. However, despite the plausibility of these hypotheses, we did not find evidence of an obesity paradox when using methods that are less prone to bias," said Virginia Chang, MD, PhD, associate professor of social and behavioral sciences at NYU College of Global Public Health and the study's lead author. The study is published online in the journal PLOS ONE.

Past research has largely looked at people with existing cardiovascular disease (prevalent disease), rather than focusing on those newly diagnosed (incident disease). Using incident disease data, however, can be valuable in helping researchers to control for confounding factors.

For instance, illness-related weight loss can influence how weight status is categorized. Disease can lead to both death and weight loss, and both are a sign of more severe disease. If people categorized as normal weight have lost weight because of more severe disease, researchers will underestimate the adverse effects of being obese relative to normal weight. In addition, those who are both obese and have severe disease are more likely to die early, while more robust obese individuals survive and are ultimately studied. Both of these biases can be reduced by examining people at the time of an incident diagnosis and using their pre-diagnosis weight.

In this study, the researchers examined the association between obesity and mortality among people with cardiovascular disease, comparing incident and prevalent disease cases in the same dataset. They used the Health and Retirement Study, a nationally representative longitudinal survey of U.S. adults aged 50 years and older conducted by the University of Michigan. The study, initiated in 1992, links surveys of more than 30,000 individuals to Medicare claims.

The researchers focused on specific cardiovascular disease diagnoses: myocardial infarction (heart attack), chronic heart failure, stroke, and ischemic heart disease. When looking at prevalent disease, the researchers used individuals' current weights; when studying incident disease, they used their pre-diagnosis weights.

Among those with prevalent disease, the researchers observed a strong and significant obesity paradox, replicating earlier findings. The risk of death was 18 to 36 percent lower for people in obese class I (a body mass index of 30-34.9) compared with those of .

However, in incident disease models of the same cardiovascular conditions, and using the same dataset, there was no evidence of this survival benefit.

"The loss of an obesity paradox when switching from prevalent to incident cases and pre-diagnosis in the same dataset suggests that prevalent models are likely biased by factors such as disease-related and selective survival," Chang said.

If obesity improved survival among people with new and existing cases of cardiovascular , the finding would have important clinical and public health implications. However, the researchers conclude that their findings do not support reevaluating guidelines in pursuit of a potential obesity paradox.

Explore further: Does carrying extra weight offer better survival following a stroke?

Related Stories

Does carrying extra weight offer better survival following a stroke?

June 29, 2017
Despite the fact that obesity increases both the risk for stroke and death, a new study has found that people who are overweight or even mildly obese survive strokes at a higher rate as compared to those with a normal body ...

Health of more than half of US adults affected by obesity

September 6, 2017
Considering weight across the life course, the prevalence of obesity among adults in the US rises considerably, suggesting that the effects on population health may be even more pervasive than previously understood, according ...

Central obesity ups mortality across BMI range

April 25, 2017
(HealthDay)—Central obesity is associated with increased risk of mortality even in normal-weight individuals, according to a study published online April 24 in the Annals of Internal Medicine.

Study shows so-called 'healthy obesity' is harmful to cardiovascular health

September 11, 2017
Clinicians are being warned not to ignore the increased cardiovascular health risks of those who are classed as either 'healthy obese' or deemed to be 'normal weight' but have metabolic abnormalities such as diabetes.

Survival rates higher in obese heart failure patients

December 22, 2014
Patients who were obese before developing heart failure lived longer than normal weight patients with the same condition according to a new study in the Journal of the American College of Cardiology that examined the "obesity ...

Study says obesity doesn't protect patients with cardiovascular disease

October 12, 2015
Demographers Samuel Preston of the University of Pennsylvania and Andrew Stokes of Boston University set out to solve a puzzle: Why is it that study after study shows obese or overweight people with cardiovascular disease ...

Recommended for you

Young children's oral bacteria may predict obesity

September 19, 2018
Weight gain trajectories in early childhood are related to the composition of oral bacteria of two-year-old children, suggesting that this understudied aspect of a child's microbiota—the collection of microorganisms, including ...

Rethinking an inflammatory receptor's obesity connection

September 12, 2018
Toll-like receptor 4 (TLR4) is a protein that plays a vital role in the body's immune response by sensing the presence of infection. It has long been thought to also sense particular types of fats, which suggested a mechanism ...

Rising European life expectancy undermined by obesity: WHO

September 12, 2018
Life expectancy in Europe continues to increase but obesity and the growing proportion of people who are overweight risks reversing this trend, the World Health Organization warned Wednesday.

Brief sleep intervention works long-term to prevent child obesity

September 6, 2018
When it comes to obesity prevention, sleep is not usually something that springs to mind, but a University of Otago research team has found we should not underestimate its importance.

Researchers develop more accurate measure of body fat

August 27, 2018
Cedars-Sinai investigators have developed a simpler and more accurate method of estimating body fat than the widely used body mass index, or BMI, with the goal of better understanding obesity.

Study suggests need to include overweight subjects in metabolic research

August 23, 2018
Children's Hospital Los Angeles investigators have demonstrated the need to include a growing constituency of obese and overweight children and adults in clinical research, with their study of a key marker for metabolism ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.