Young adults who remain obese for two decades or more double their risk of developing a marker of heart disease in middle age, a study found.
Every year of obesity raises the risk of developing coronary artery calcification, a silent predictor of heart disease with mild to no symptoms, by 2 percent to 4 percent, according to research Wednesday in the Journal of the American Medical Association.
More than one-third of U.S. adults ages 20 and older, and 17 percent of children and teenagers, are obese, according to the U.S. National Institutes of Health.
Wednesday's study is the first to show that how long a person is obese can independently contribute to heart risk, said Jared Reis, the lead study author.
"What our study suggests is if we're measuring only body mass index and waist circumference we may be underestimating the health risks of obesity by not measuring the duration," Reis, an epidemiologist at the NIH's National Heart, Lung, and Blood Institute in Bethesda, Md., said in a telephone interview.
Researchers looked at 3,275 adults ages 18 to 30 years who weren't obese at the beginning of the study in the mid-1980s. Those in the study were given computed tomography scans to detect coronary artery calcification over 25 years. Their obesity and abdominal obesity also was measured.
The researchers found that about 38 percent of those who were obese for more than 20 years and 39 percent of those who had abdominal obesity for that time developed coronary artery calcification compared with 25 percent of those who never became obese and never developed abdominal obesity.
Those in the study who had obesity and abdominal obesity over two decades or more also had their coronary artery calcification progress in their heart.
Obesity is measured using body mass index, or BMI, a calculation of weight and height. For example, a 5-foot, 4-inch woman weighing 175 pounds has a BMI of 30. BMI of 30 or more is considered obese, while a BMI of 25 to 29.9 is considered overweight, according to the National Institutes of Health.