DALLAS — Waist girth and exercise tolerance each gave significant prognostic information about a person's risk for cardiovascular death or coronary events that went beyond the Framingham risk score, according to data collected from more than 30,000 people.
As a result of these findings, “we're planning to incorporate waist girth and exercise tolerance into our use of the Framingham risk score,” Radim Jurca, Ph.D., said at the annual scientific sessions of the American Heart Association.
Dr. Jurca and his associates assessed the prognostic role of waist girth using data collected from 33,192 men who were without symptoms of coronary heart disease or cardiovascular disease when they underwent a baseline examination at the Cooper Clinic in Dallas during 1979–2003. Waist girth was measured with a tape at the umbilicus. The men were then followed for an average of 14 years, during which time there were 624 cardiovascular deaths, 366 coronary heart disease deaths, and 680 “hard” coronary events that were either coronary deaths or nonfatal myocardial infarctions.
The researchers divided the group into tertiles of about 11,000 men each, defining groups with a waist girth of less than 89 cm, of 89–97 cm, or above 97 cm.
The incidence of cardiovascular and coronary events tracked with increases in waist girth. For example, the rate of cardiovascular disease deaths during the 14 years of follow-up was about 0.010% among men in the lowest waist-girth tertile, about 0.012% among those with a girth of 89–97 cm, and about 0.020% among those in the highest tertile, a linear trend that was statistically significant after adjustment for age, examination year, and the Framingham risk score.
In a regression model the risk of cardiovascular death rose by 17% for every 5-cm increase in waist girth, said Dr. Jurca, an exercise physiologist at the Cooper Institute in Dallas.
Similar analyses showed that a 5-cm increase in girth boosted the risk of coronary deaths by 11%, and the risk of coronary events by 15%.
A similar calculation was done substituting exercise tolerance for waist girth. In this case, the study group included 12,805 women and 41,708 men who were asymptomatic at the time of their first examination during 1970–2002. They were followed for an average of 17 years.
The analysis showed that for each metabolic equivalent that exercise capacity increased, a person's risk of cardiovascular death, coronary death, or a hard coronary event was reduced by about 20%, Michael J. LaMonte, Ph.D., said in a separate report at the meeting.
This effect was statistically independent of the Framingham risk score, as well as age, examination year, family history of cardiovascular disease or diabetes, and ECG abnormalities, said Dr. LaMonte, director of epidemiology at the Cooper Institute.