About the National Health and Nutrition Examination Survey

The National Health and Nutrition Examination Survey (NHANES) is a nationwide program that assesses the health and nutritional status of adults and children in the United States. Unlike most surveys, NHANES combines interviews and physical examinations, providing a comprehensive look at public health. It is a key initiative of the National Center for Health Statistics (NCHS), a division of the Centers for Disease Control and Prevention (CDC) responsible for collecting critical health data for the nation.

Launched in the early 1960s, NHANES initially operated as a series of periodic surveys, each focusing on different population groups or health issues. Since 1999, it has been conducted continuously, adapting to emerging health and nutrition concerns. NHANES examines a nationally representative sample of approximately 5,000 individuals across the U.S. each year, selecting 15 counties annually to ensure broad representation.

The survey includes demographic, socioeconomic, dietary, and health-related interviews, followed by medical, dental, and physiological examinations trained medical professionals perform. Findings help track the prevalence of diseases and risk factors, assess nutritional health, and establish national standards for key health indicators like height, weight, and blood pressure. The data also support epidemiological research and inform public health policies and programs.

Survey Content

NHANES collects data on chronic health conditions, including diagnosed and undiagnosed illnesses. It evaluates key risk factors, such as smoking, alcohol use, drug use, physical activity, and diet, and studies aspects of reproductive health, including contraceptive use and breastfeeding practices.

The survey examines various medical conditions and health indicators, including cardiovascular disease, diabetes, obesity, kidney disease, respiratory conditions, infectious diseases, vision and hearing loss, osteoporosis, and environmental exposures. To ensure reliable data, NHANES oversamples older adults, African Americans, and Hispanics, who often face higher health risks.

With an aging U.S. population, NHANES is crucial in understanding healthcare needs, public policy implications, and research priorities. Participants undergo dietary interviews, body measurements, and medical exams, with most blood samples and dental screenings included. The extent of testing varies by age, with older participants receiving more comprehensive assessments.

Survey Operations

NHANES conducts health interviews in participants’ homes and performs medical examinations in mobile centers that travel nationwide. These mobile units are equipped with state-of-the-art technology and staffed by physicians, medical technicians, and interviewers, many of whom are bilingual in English and Spanish to accommodate diverse participants.

NHANES employs advanced data collection systems, minimizing paper use and manual errors. Interviewers use notebook computers with electronic pens, and medical data is automatically transmitted via digital scales, stadiometers, and touch-screen computers for secure and efficient processing. It enables the National Center for Health Statistics (NCHS) to access survey data within 24 hours, ensuring high-quality information is rapidly available for analysis.

Before visiting an area, NHANES notifies local health and government officials, and households receive a letter from the NCHS Director explaining the survey. The program is designed to encourage participation, offering transportation if needed, compensation, and a report of medical findings. All collected information remains strictly confidential and is protected under public laws.

Uses of the Data

NHANES data is widely used by researchers, universities, healthcare providers, and government agencies, including the National Institutes of Health (NIH), the Food and Drug Administration (FDA), and the Centers for Disease Control and Prevention (CDC). The U.S. Department of Agriculture (USDA) collaborates on nutrition data, and NHANES partners with the Environmental Protection Agency (EPA) to study environmental health impacts.

Past NHANES data have led to significant public health advancements, such as:

• Growth charts are used by pediatricians worldwide to track children's development.
• Blood lead research has helped remove lead from gasoline and food containers, reducing lead exposure by over 70% since the 1970s.
• Obesity tracking that fueled nationwide initiatives promoting diet and exercise.
• Diabetes awareness programs, especially targeting minority populations where undiagnosed cases remain high.

NHANES also plays a crucial role in shaping FDA regulations on vitamin and mineral fortification and guiding public health campaigns on hypertension, cholesterol, and heart disease prevention. New lung function measurements improve asthma and respiratory disease research, while ongoing data collection ensures annual health estimates for various conditions.

By monitoring health trends over time, NHANES helps policymakers, researchers, and public health officials develop targeted programs, improve healthcare strategies, and create effective disease prevention initiatives, ultimately enhancing public health in the United States.