Obesity weighs heavy on heart: study
Heart attacks are hitting the overweight more than a decade sooner than "normal" weight people, researchers are reporting.
SHARON KIRKEY, Canwest News Service, September 22, 2008
A study of more than 111,000 people is one of the first to put real numbers to the risk of obesity and suggests "excess adiposity" - fat tissue - is more dangerous to the heart than smoking.
"The leading theory in cardiology right now is that the fat tissue is actually producing factors that precipitate heart attacks," said lead author Peter McCullough, consultant cardiologist and chief of nutrition and prevention medicine at William Beaumont Hospital in Royal Oak, Mich. The theory is that cholesterol builds up in the coronary arteries and inflammatory or other chemicals produced by fat cells trigger the plaque to suddenly rupture, causing a blood clot to form and unleashing an acute heart attack.
Earlier studies "just didn't have enough patients of different body sizes having their first heart attack to really evaluate" whether obesity is associated with premature heart attacks, McCullough said.
His team analyzed data from a nationwide U.S. registry of people hospitalized for heart attack and unstable angina, or chest pain, from 2001 to 2007.
A total of 111,847 men and women who had experienced a first heart attack were included in the analysis. They were grouped according to their body mass index, or BMI, a measure of body fat based on height and weight.
Researchers found that, the heavier the person, the younger the age of a first heart attack. The most obese people had their heart attacks when they were 59, on average.
That compares with about 75 for the leanest group (average body weight of about 103 pounds, meaning they were considered underweight), and 71 for people of "normal" weight, where the average weight is about 142 pounds.
The most obese group had a BMI of 40 or more and weighed on average 280 pounds. The rate of diabetes was 17 per cent in the leanest group, and 49 per cent in the most obese.
"You can get a feeling of how obesity-driven diabetes is," McCullough said.
All the patients, regardless of body size, had about the same level of LDL cholesterol, the so-called bad cholesterol thought to be a major risk factor for heart attacks. That means the excess fat is causing heart disease in other ways, McCullough said. Rates of smoking were equal across the board: "We really can't blame it on smoking."
"Those patients at the highest body weight on average lost 12 years of life before their first heart attack." The second most important factor was smoking, "where they lost just under 10 years of life before a first heart attack.
"This is really the first study that shows that some factors are more powerful than smoking in terms of the prematurity of myocardial infarction (a heart attack)," McCullough said.
The study involved a type of heart attack called non-ST-segment elevation myocardial infarction. They always require hospitalization and have an in-hospital fatality rate of about 10 per cent, and about 20 per cent over the next six months, McCullough said.
"They are not trivial events. They account for a leading cause of patients to lose time away from work and actually seek medical disability."
The study clearly shows "that, contrary to some of the arguments out there about whether or not excess weight may be protective ... there is a tremendous risk difference in terms of having your first heart attack if you are overweight or obese," said. Arya Sharma, chair of obesity research and management at the University of Alberta in Edmonton.
"You're having a heart attack a decade before those who don't have a weight problem," Sharma said. "And 59 is actually a very young age. These are people who aren't even close to retirement."
McCullough says people could reduce their risk of cardiovascular disease by losing weight and body fat. According to the Canadian Community Health Survey, 23 per cent of Canadians 18 and older are obese.
The study appears in the most recent issue of the Journal of the American College of Cardiology.
© The Gazette (Montreal) 2008