WHAT: The length of time a young adult is obese is associated with the development of silent, or subclinical, heart disease in middle age, independent of body mass index (BMI) or waist circumference, according to National Institutes of Health-supported research.

Each year that a young adult is obese increases that person's risk of developing coronary artery calcification, a subclinical predictor of heart disease, by 2 to 4 percent.

These findings were published today in the Journal of the American Medical Association.

Obesity is a risk factor for subclinical heart disease, when people exhibit mild or no symptoms so it's seemingly silent. This is the first known study to show that a longer duration of obesity also contributes independently to the development of subclinical heart disease.

The researchers collected and examined data from 3,275 Caucasian and African-American adults, ages 18-30 years, who were enrolled in the NIH's National Heart, Lung, and Blood Institute- (NHLBI) supported Coronary Artery Risk Development in Young Adults Study (CARDIA) in the mid-1980s, around the start of the obesity epidemic in the United States.

The study participants were recruited from Birmingham, Ala.; Chicago; Minneapolis; and Oakland, Calif., and followed for 25 years, from young adulthood to middle age. Every 2 to 5 years, participants were examined to determine if and when they became obese and how long they stayed obese. CT scans given at years 15, 20, or 25 determined the presence of coronary artery calcification.

Since the mid-1980s, obesity has become increasingly prevalent in the United States with over one-third of adults now obese. In addition, people are becoming more obese at earlier ages. The study results suggest that this trend of increasing lifelong obesity may have important implications for the future burden of subclinical heart disease and potentially for rates of clinical heart disease in the United States.

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