The National Health and Nutrition Examination Survey III (NHANES III) was a periodic survey carried out by the National Center for Health Statistics (NCHS), under the Centers for Disease Control and Prevention (CDC). It evaluated the health and nutritional status of adults and children across the United States. NHANES III provided a detailed overview of American health, serving as a valuable resource for public health understanding.
Purpose and Design
NHANES III’s goals included monitoring health and nutrition trends, identifying health disparities, and providing data for epidemiological research. The survey was conducted in two phases (1988-1991 and 1991-1994), allowing for a nationally representative sample of the U.S. population.
Methodology involved household interviews, physical examinations in mobile examination centers (MECs), and laboratory tests. Approximately 40,000 individuals, aged 2 months and older, participated. A home examination option was introduced for very young children and elderly individuals who could not visit MECs. Children aged 2 months through 5 years, adults 60 and older, Black individuals, and people of Mexican origin were oversampled to provide precise health information for these groups.
Types of Data Collected
NHANES III gathered data across several categories, providing a snapshot of the nation’s health. Demographic information included age, sex, race/ethnicity, and socioeconomic status, allowing for analyses of health patterns. Dietary intake included food consumption patterns and nutrient intake, offering insights into nutritional habits.
Anthropometric measurements like height, weight, waist circumference, and BMI assessed body composition and physical development trends. Clinical measurements covered health indicators like blood pressure, vision, hearing, dental health, and respiratory function, providing information on condition prevalence. Laboratory analyses of blood and urine samples determined indicators like cholesterol, glucose, iron status, lead levels, nutritional biomarkers, and environmental exposures. Participants also provided self-reported data on chronic diseases and health behaviors, such as smoking and physical activity, contributing to understanding health conditions and lifestyle factors.
Significant Health Discoveries
NHANES III data provided early and substantial evidence regarding the escalating obesity epidemic in the United States. The survey documented a rising prevalence of overweight and obesity across various age and demographic groups, highlighting a growing public health challenge. These findings were instrumental in recognizing the widespread nature of excess adiposity in the population.
The survey also offered valuable insights into cardiovascular risk factors, specifically the prevalence, awareness, treatment, and control of hypertension and high cholesterol levels. For instance, NHANES data revealed that a significant percentage of adults with high blood pressure were unaware of their condition, underscoring the need for increased screening. A notable achievement involved documenting significant declines in blood lead levels in children, which reflected the success of public health interventions like the ban on leaded gasoline. By the 1990s, only about 4% of Americans had elevated blood lead levels, a substantial reduction from previous decades.
Furthermore, NHANES III identified specific vitamin and mineral deficiencies or excesses within various population subgroups. The survey also contributed to a deeper understanding of the prevalence and associated risk factors for diabetes in the U.S. population. These discoveries provided a scientific basis for targeted public health efforts and continued monitoring of these conditions.
Influence on Public Health and Policy
The extensive data gathered by NHANES III has been widely utilized to inform public health initiatives and shape policy decisions. The findings directly influenced the development of national dietary guidelines and the creation of public health campaigns, particularly those focused on preventing obesity and promoting healthy lifestyles. This robust dataset served as a foundational resource for understanding the health status of the U.S. population during that period.
NHANES III established critical baseline data, which has been used for long-term surveillance of chronic diseases and their associated risk factors. This long-term monitoring capability allows for tracking changes in disease prevalence and the effectiveness of interventions over time. The survey data also became a widely used resource for numerous epidemiological studies and academic research projects, contributing to a broader scientific understanding of health and disease.
The insights from NHANES III have guided the allocation of public health funding and the implementation of targeted interventions based on identified health needs and disparities. For example, data on lead exposure provided evidence to support regulatory actions aimed at reducing environmental toxins. The comprehensive nature of the data and its detailed analysis have provided a strong evidence base for public health actions and policy development for decades.