Rancho Bernardo Study: results show new predictors of CAC progression

Blood pressure, fasting plasma glucose were better independent predictors than metabolic syndrome.

In older adults with no known history of heart disease, systolic blood pressure and fasting plasma glucose were independently associated with coronary artery calcium progression whereas metabolic syndrome was not, according to findings from the Rancho Bernardo Study.

The Rancho Bernardo Study is a community-based study of upper- and middle-class white adults living in California that began in 1972. These results were from an analysis of the association between metabolic syndrome and its components with coronary artery calcium progression.

The researchers enrolled 338 older adults (182 women) without known heart disease. All participants had measurements of heart disease risk factors and coronary artery calcium during 4.5 years. Coronary artery calcium progression was defined as an increase in total coronary artery calcium score ≥2.5 mm³.

“The prevalence of metabolic syndrome in this older Caucasian population without known coronary heart disease was 11.8% to 15.1% depending on metabolic syndrome definition; metabolic syndrome by either definition was not an independent predictor of coronary artery calcium progression,” the researchers wrote.

At baseline, 15.1% (44 of 292) of the participants had metabolic syndrome based on the World Health Organization definition compared with 11.8% (40 of 338) of the participants based on the National Cholesterol Education Program Adult Treatment Panel (ATP) III definition. In total, 5.3% (18 of 292) of the participants met both criteria for metabolic syndrome.

Nearly half of the participants experienced coronary artery calcium progression. Neither metabolic syndrome definition predicted progression, according to logistic regression analysis adjusted for age, sex, smoking status and LDL.

The researchers discovered an independent association with hypertension and coronary artery calcium progression (OR=2.11; 95% CI, 1.33-3.30), one component of the metabolic syndrome. FPG (>100 mg/dL) independently predicted coronary artery calcium progression (OR=2.3; 95% CI, 1.01-5.50); however, it was only in participants aged younger than 65 years (n=118).

“These results highlight the importance of these reversible risk factors in older adults,” the researchers wrote.

Participants with metabolic syndrome by the WHO definition experienced greater total change in coronary artery calcium volume score compared with patients without metabolic syndrome by this definition (102 mm³ vs. 22.9 mm³; P=.001). Metabolic syndrome by the ATP III definition was not associated with any significant change in coronary artery calcium volume change.

“Metabolic syndrome defined by WHO was superior to that defined by ATP III in predicting subclinical atherosclerosis by coronary artery calcium scores. When other classical heart disease risk factors were included, the presence of the metabolic syndrome itself did not predict coronary artery calcium progression, but two of its components, systolic BP and FPG, were independently associated with coronary artery calcium changes,” they wrote. – by Katie Kalvaitis

Diabetes Care. 2009;32:141-146.

The magnitude of coronary artery calcification reflects atherosclerotic burden and provides meaningful information regarding cardiovascular disease risk, especially when complemented by Framingham risk scores. The current thinking is that determination of a coronary calcium score helps identify asymptomatic patients at risk for future myocardial infarction or other CV events. To date, it is known that duration and magnitude of BP elevation independently predicts a more rapid progression of coronary calcification. Additionally, other aspects of metabolic syndrome, such as cholesterol and its subunits, have variable effects on coronary calcification. There are no data available, however, on fasting glucose levels and coronary artery calcification progression.

The results presented by Kramer et al from the Rancho Bernardo Study point out important new information about progression of coronary artery calcification while confirming established risk factors. No significant difference in coronary artery calcium volume was noted as defined by ATP III metabolic syndrome status. Moreover, after adjustment for age, sex, smoking status and LDL, neither WHO– nor ATP III–defined metabolic syndrome predicted progression of coronary artery calcification. Although the researchers confirmed previous data that hypertension is an independent risk factor for progression of coronary artery calcification, the novel finding was that FPG >100 mg/dL was an independent predictor of calcification progression. It should be noted that this finding of glucose driving the risk was seen in people aged younger than 65 years, which, in my opinion, makes it even more important since duration of risk factor burden for many of these processes is key to staving off future disease.

– George Bakris, MD

Endocrine Today Editorial Board member