Trends in Risk Factors in the United States, 1971-1975 v. 1999-2002

Background. In the past few decades, some measures of population risk have improved, while others have deteriorated. Understanding the health of the population requires integrating these different trends. We compare the risk factor profile of the population in the early 1970s with that of the population in the early 2000s.

Methods. Data from the NHANES I (1971-1975) and NHANES 1999-2002 are used to measure demographics, smoking, drinking, obesity, blood pressure, and cholesterol. Using the NHANES I epidemiological follow-up, we estimate the impact of each risk factor on 10 year mortality rates. We compare the predicted 10 year mortality for the NHANES I and NHANES 1999-2002 cohorts.

Results. For the population aged 20-74, the 10 year probability of death fell from 9.8 percent in 1971-75 to 8.4 percent in 1999-2002 (p<.001). Among the population aged 55-74, the 10 year risk of death falls from 25.7 percent to 21.7 percent (p<.001). The largest contributors to these changes are the reduction in smoking and better control of blood pressure. Increased obesity increased risk, but not by as large a quantitative amount.

Conclusions. Despite substantial increases in obesity in the past three decades, the overall population risk profile is healthier now than it was formerly. Both behavioral changes and medical care have reduced risk. Mortality rates may thus continue to decline.