Secular Trends in Cardiovascular Disease Risk Factors According to Body Mass Index in U.S. Adults

The prevalence of obesity in adults has risen from 13% to 31% in the past 25 years. The trend is evident in both men and women and in all age and racial/ethnic groups. Prospective cohort studies have shown convincingly that obese persons are at increased risk for several poor health outcomes, including hypertension, diabetes, cardiovascular disease (CVD), disability in general, and mortality. The investigators analyzed 40-year trends in CVD risk factors as related to body mass index (BMI) in 5 nationally representative cross-sectional surveys: the National Health Examination Survey (1960–1962), the National Health and Nutrition Examination Survey (NHANES) I (1971–1975), II (1976–1980), and III (1988–1994), and NHANES 1999–2000. The criterion BMI for overweight was 25–29 kg/m2 and for obesity, 30 kg/m2 and higher. A high cholesterol level was defined as 240 mg/dL or above, and the criterion blood pressure was 140/90 mm Hg. The mean BMI increased from 33.6 kg/m2 in 1960–1962 to 35.8 kg/m2 in 1999–2000. Although there were large reductions (33–52% compared with baseline) in high blood cholesterol, high blood pressure, and smoking over the past 30 to 40 years, the prevalence of obesity and diagnosed diabetes doubled during the same period. Overweight and obese individuals had greater reductions in high cholesterol between 1960 and 2000 than did lean persons. Whereas obese persons had a 9% to 12% higher prevalence of elevated blood cholesterol than did lean persons across all surveys, by 1999–2000, the difference was only 2.7%. Reductions in elevated cholesterol were significantly greater in the obese and overweight groups than in lean persons. High blood pressure also tended to decrease more over time in obese and overweight individuals compared with the lean group. Nevertheless, obese persons were hypertensive at least twice as often as lean persons in 1999–2000 (24% vs 11%). Across all surveys, smoking was least prevalent in obese persons and most frequent in lean persons. In all BMI groups, the prevalence fell by 12% to 13%. The prevalence of total (diagnosed and undiagnosed) diabetes remained stable over time in all BMI groups, but the prevalence of diagnosed diabetes was 2.5- to 3.5-fold higher in 2000 as in 1960 in overweight and obese individuals. In all BMI groups, the proportion of persons treated for high cholesterol and high blood pressure increased. Treatment of high blood cholesterol increased more in the obese group than in lean persons. Treatment for high blood pressure increased significantly more in the obese and overweight than in lean persons. Despite favorable trends in the past 25 years, a substantial number of lean as well as obese individuals still have increases in modifiable CVD risk factors. It is important that public health efforts target lean people as well as those who are overweight or obese.