Best Prediction for Calcified Arteries in Middle Age Starts Early

BETHESDA, Md., April 30 -- Heart disease risk factors in early adulthood presage atherosclerosis in middle age, suggesting that early intervention may be beneficial, researchers found.

Smoking, body mass index, blood pressure, cholesterol and glucose levels at ages 18 to 30 predicted coronary calcification 15 years later, at ages 33 to 45, as well as or better than risk levels in the intervening 15 years, said Catherine M. Loria, Ph.D., of the National Heart, Lung, and Blood Institute, and colleagues.

"Earlier risk assessment and efforts to achieve and maintain optimal risk factor levels may be needed," the investigators reported in the April 24 issue of the Journal of the American College of Cardiology.

American Heart Association guidelines call for blood pressure and body mass index assessment at least every two years and cholesterol and glucose testing at least every five years beginning at age 20.

However, "fewer young adults report being screened for serum cholesterol than older adults," the investigators noted. "A common approach is to wait until risk factors develop to prescribe lifestyle changes or pharmacological treatment, rather than prevent or delay the onset of risk factors."

In a prospective study, called Coronary Artery Risk Development in Young Adults (CARDIA), the investigators enrolled 3,043 African American and white participants in four U.S. cities, conducting examinations for risk factors at baseline and years two, five, seven, 10, and 15.

Initially, few participants had elevated risk factor levels using thresholds set for older adults. LDLs at or above 130 mg/dL were present among 6%. Two percent had blood pressure at or above 120/80 mm Hg. Less than 1% had serum glucose at or above 110 mg/dL. However, 34% were overweight or obese, and 25% smoked cigarettes.

By year 15, 30% had above optimal LDL cholesterol levels, 35% had high blood pressure, 67% were overweight or obese, and 19% smoked cigarettes.

When coronary artery calcification was measured at year 15 using computed tomography imaging, 9.6% had detectable calcification. Half of the Agatston scores were below 20.

To find at which time point the risk factors were most predictive of calcification, the researchers used C-statistics, a measure of sensitivity and specificity of a model.

They found that the model of risk factor levels at baseline was better than that for year 15 (0.79 vs. 0.77, P=0.019) but the same as that for 15-year averages (0.79 vs. 0.79, P=0.8262).

Among the findings for baseline risk factors predicting coronary artery calcification by age 33 to 45, the researchers reported:

• LDL cholesterol at or above 130 mg/dL increased the odds of calcification (odds ratio 2.23, 95% confidence interval 1.68 to 2.98).
• Blood pressure at least 120/80 mm Hg increased the likelihood of calcification (OR 1.52, 95% CI 1.12 to 2.06).
• BMI above 25 kg/m2 increased the odds (OR 1.62, 95% CI 1.21 to 2.17).
• Glucose at or above 110 mg/dL increased the odds (3.04, 95% CI 1.20 to 7.68).
• Odds of any calcification were 40% higher for every 10 cigarettes smoked.
• The likelihood of calcification was 50% higher per 30 mg/dL LDL cholesterol.
• The odds were 20% higher each for each 10 mm Hg systolic blood pressure and 15 mg/dL blood glucose.

While previous studies had shown that these factors were predictive, there had been no evidence for the optimal timing of risk assessment.

The findings are good news for patients, Dr. Loria and colleagues determined.

"If early adult levels predict cardiovascular risk as well as levels measured in middle age, augmented efforts to encourage young adults to achieve and maintain optimal risk factor levels might lead to more adults reaching middle age at low risk for cardiovascular risk," they wrote.

They encouraged physicians to start preventive efforts before modifiable risk factor levels reach clinical guideline thresholds, since plaque calcification is already underway and accelerates toward middle age.