Overweight and obese heart failure patients outlived their normal-weight patients even after adjustment for various factors, researchers found.
Among patients with incident heart failure, overweight and obese patients had lower mortality rates compared to normal-weight patients, (hazard ratio (HR) 0.72, and 0.70, respectively), Dr Umair Khalid of Baylor College of Medicine in Houston, Texas, and colleagues report. MedPageToday reports that the Atherosclerosis Risk In Communities (ARCI) study was an ongoing study involving 15,792 men and women who were ages 45 to 64 when they were recruited from 1987 to 1989. Participants came from one of four communities spread across the US.
Khalid and colleagues looked at 1,487 patients from the ARCI study who had heart failure. The group was 54% male, 66% white, and had an average age of 67. The researchers measured body mass index (BMI) at least 6 months prior to incident heart failure and again at the time of death.
Among the patients, 35% were overweight and 47% were obese. The pre-morbid BMI was measured an average of 4.3 years (±3.1) before the diagnosis of heart failure. Throughout the 10-year follow-up period, 43% of the heart failure patients died.
Adjustments were made for hypertension, history of myocardial infarction, coronary heart disease, diabetes, stroke, and demographics.
Compared with the normal-weight group, and after adjustments, overweight patients had a lower risk of dying (HR 0.72, 95% CI 0.58-0.90, P=0.004), and obese patients had an even lower risk of dying (HR 0.70, 95% CI 0.56-0.87, P=0.001).
The phenomenon of excess weight appearing to protect patients is known as the "obesity paradox," and in the case of this cohort, the protection did not change significantly based on smoking status, history of cancer, or diabetes status.
The authors noted that the "obesity paradox" is not uncommon in heart failure development, and that although several studies have investigated this link, the longitudinal nature of this study allows for an independent association between higher pre-morbid BMI and long-term survival advantage.
Several factors could explain the study results. The investigators suggested that obese patients could have a higher metabolic reserve compared with normal-weight patients and thus have a survival advantage when cardiac cachexia follows the development of heart failure.
Wang agreed that cardiac cachexia and muscle wasting in late-stage heart failure could explain the protective function of excess body weight.
Another possible theory the authors posed was that obesity alters the natural history of heart failure through neuro-humoral pathways. Also, these results could be a survivor effect, as frailer older adults die sooner.
The researchers listed the observational design of the study and its reliance on ICD-9 codes as potential study limitations.
However, many people who are overweight but seem otherwise healthy will eventually have an unhealthy increase in blood pressure and other metabolic risk factors over a 20-year period, a new study suggests. Most "healthy obesity" becomes unhealthy obesity over time, reports Reuters Health.
"These results were not overly surprising, as we already know that healthy obese adults have a greater risk for developing type 2 diabetes and cardiovascular disease than healthy normal-weight adults," said lead author Joshua A Bell of University College London.
In earlier, shorter studies, about a third of healthy obese adults progressed to unhealthy obesity, Bell said. His new study, which tracked people for at least 10 years longer than those earlier studies did, "indicates that this tendency gets stronger with time, with about half making this transition after 20 years," he said.
Healthy obesity is often just a phase, he added.
Bell’s team used data from an ongoing study of more than 2,500 British civil servants, with health metrics collected every five years.
In 1992, 66 participants were classified as "healthy obese." Although extremely overweight, they had no more than one of the following metabolic risk factors: low levels of "good" HDL cholesterol, high blood pressure or use of blood pressure medication, high fasting blood sugar levels, insulin resistance, or use of medication for diabetes.
After 20 years, 34 of the "healthy obese" – just over half of the original number – had added more of the metabolic risk factors and had become "unhealthy obese," the researchers estimated.
The researchers report that 10% of the original healthy obese group had lost weight and were "healthy non-obese" by the 20-year mark, while the remaining 38% stayed in the healthy obese group for the duration.
Overall, those who started as healthy obese were almost eight times more likely to have become unhealthy obese than those who started at a healthy weight.
"Our results stress the need to take a long-term view of healthy obesity," Bell said. He added, "Healthy obesity is still a high risk state – the harmful effects may just be delayed."
[link url="http://www.medpagetoday.com/Endocrinology/Obesity/49268"]Full MedPageToday report[/link]
[link url="http://content.onlinejacc.org/article.aspx?articleid=2085758&resultClick=3"]Journal of the American College of Cardiology abstract[/link]
[link url="http://www.reuters.com/article/2015/01/06/us-healthy-obesity-idUSKBN0KF1P820150106"]Full Reuters Health report[/link]
[link url="http://content.onlinejacc.org/article.aspx?articleID=2087915"]Journal of the American College of Cardiology abstract[/link]