Cardiovascular risk factors have declined substantially over past 40 years

Prevalence of high cholesterol levels, hypertension and smoking, particularly among overweight and obese adults, have declined considerably over the past 40 years, according to a study in the April 20 issue of JAMA. This trend was not true for diabetes, which has had a stable prevalence.

The association between the increase in obesity in the U.S. population and cardiovascular disease (CVD) risk factors has been uncertain. according to background information in the article.

Edward W. Gregg, Ph.D., of the Centers for Disease Control and Prevention, Atlanta, and colleagues analyzed data from 5 NHANES conducted during the last 40 years and examined whether long-term changes in levels of key cardiovascular risk factors have been different in overweight or obese persons compared with lean persons. The risk factors included prevalence of high cholesterol levels (240 mg/dL or greater [6.2 mmol/L or greater] regardless of treatment), high blood pressure (140/90 mm Hg or greater regardless of treatment), current smoking, and total diabetes (diagnosed and undiagnosed combined) according to BMI group (lean, less than 25; overweight, 25-29; and obese, 30 or greater).

The researchers found: "In this unique series of nationally representative surveys of the U.S. adult population, we documented a substantial decline in the prevalence of key CVD risk factors over the last 3 to 4 decades, affecting obese, overweight, and lean segments of the population. Among obese persons today, prevalence of high cholesterol, high blood pressure, and smoking are now 21, 18, and 12 percentage points lower, respectively, than among obese persons 30 to 40 years ago. The corresponding reductions among lean persons have been somewhat less, with average declines of 12 to 14 percentage points. Although obesity remains associated with a higher prevalence of important CVD risk factors, differences in total cholesterol levels across BMI groups may be narrowing, and for blood pressure and smoking improvements have been similar across BMI groups. Thus, obese and overweight persons may be at lower risk of CVD now than in previous eras."

"Diabetes is a notable exception to the observed reduction in risk factors, as prevalence of total diabetes (i.e., diagnosed and undiagnosed combined) did not decrease within BMI groups. This was accompanied by a 55 percent increase in total diabetes among the overall population (i.e., all BMI groups combined), presumably due to an increasing proportion of the population moving into the obese categories," the authors write.

"Despite our encouraging findings, a considerable proportion of lean as well as obese persons still have elevated levels of modifiable risk factors, particularly when one considers that the current definitions of risk factor control are more aggressive than the definitions used in this trend analyses. Clinical and public health efforts should continue to emphasize maintenance of healthy lifestyle behaviors for both lean as well as overweight and obese persons," the authors conclude.