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Duration of Obesity May Affect Heart Disease

How long a young adult is obese may affect that person’s heart disease risk in middle age, according to new research. The finding suggests that not only preventing but also delaying the onset of obesity can help reduce heart disease later in life.

Coronary heart disease is the leading cause of death nationwide for both men and women. Many risk factors can be modified to help prevent or delay the disease. However, heart disease develops slowly over time. It’s often diagnosed after a person has the signs or symptoms of a heart attack, heart failure or arrhythmia (an irregular heartbeat). Before any warning signs appear — or are noticed — the condition is called subclinical or “silent” heart disease.

Obesity is a known risk factor for heart disease. Past studies have linked both body mass index (BMI) — a ratio of weight to height — and waist circumference to heart disease risk. However, few studies have examined whether the duration of obesity affects heart disease as well. A team led by Dr. Jared P. Reis of NIH’s National Heart, Lung and Blood Institute (NHLBI) set out to investigate.

The researchers collected and examined data from more than 3,200 Caucasian and African-American young adults, 18-30 years old, who were enrolled in the NHLBI-supported Coronary Artery Risk Development in Young Adults (CARDIA) study in the mid-1980s. The participants were recruited from Birmingham, Alabama; Chicago; Minneapolis; and Oakland, California.

Every 2 to 5 years, the 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 — a subclinical sign of heart disease. The findings were published on July 17, 2013, in the Journal of the American Medical Association.

About 40% of participants became obese during the study. Over 38% of those who were obese for more than 20 years developed coronary artery calcification. In contrast, only about 25% of those who never became obese developed coronary artery calcification. The scientists calculated that, independent of BMI or waist circumference, each year that a young adult is obese raises that person’s risk of developing silent heart disease by 2-4%.

Obesity has become increasingly prevalent in the United States. People are becoming obese at younger ages, and more than one-third of adults nationwide are now obese. These findings suggest that current trends may have important implications for heart disease.

“I think our findings really suggest that if we don’t measure obesity duration in addition to BMI and waist circumference, we may be underestimating the health risks of obesity,” Reis says.

The researchers now plan to investigate the relationship between duration of obesity and clinical heart disease.