National Health Interview Survey
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The National Health Interview Survey (NHIS) is an annual, cross-sectional survey intended to provide nationally representative estimates on a wide range of health status and utilization measures among the nonmilitary, noninstitutionalized population of the United States. Each annual data set can be used to examine the
disease burden Disease burden is the impact of a health problem as measured by financial cost, mortality, morbidity, or other indicators. It is often quantified in terms of quality-adjusted life years (QALYs) or disability-adjusted life years (DALYs). Bot ...
and access to care that individuals and families are currently experiencing in the United States. NHIS is designed by the
CDC The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georgi ...
's National Center for Health Statistics (NCHS) – the government agency tasked to monitor the population's health status and behavior – and administered by the
U.S. Census Bureau The United States Census Bureau (USCB), officially the Bureau of the Census, is a principal agency of the U.S. Federal Statistical System, responsible for producing data about the American people and economy. The Census Bureau is part of the ...
. NHIS has been administered since 1957, although the core content and
questionnaires A questionnaire is a research instrument that consists of a set of questions (or other types of prompts) for the purpose of gathering information from respondents through survey or statistical study. A research questionnaire is typically a mix of ...
undergo major revisions every 10–15 years. NHIS allows both governmental and outside
researchers Research is "creative and systematic work undertaken to increase the stock of knowledge". It involves the collection, organization and analysis of evidence to increase understanding of a topic, characterized by a particular attentiveness t ...
to obtain estimates on a variety of health-related topics among either the entire nation or specific
demographic groups Demography () is the statistics, statistical study of populations, especially human beings. Demographic analysis examines and measures the dimensions and Population dynamics, dynamics of populations; it can cover whole societies or groups ...
of the population. Also, since the survey design is
cross-sectional Cross-sectional data, or a cross section of a study population, in statistics and econometrics, is a type of data collected by observing many subjects (such as individuals, firms, countries, or regions) at the one point or period of time. The anal ...
rather than
longitudinal Longitudinal is a geometric term of location which may refer to: * Longitude ** Line of longitude, also called a meridian * Longitudinal engine, an internal combustion engine in which the crankshaft is oriented along the long axis of the vehicl ...
, health information can be trended for
demographic groups Demography () is the statistics, statistical study of populations, especially human beings. Demographic analysis examines and measures the dimensions and Population dynamics, dynamics of populations; it can cover whole societies or groups ...
and the country as a whole, but not for individuals or families.


History

Authorized by th
National Health Survey Act
of 1956, the
U.S. Public Health Service The United States Public Health Service (USPHS or PHS) is a collection of agencies of the Department of Health and Human Services concerned with public health, containing nine out of the department's twelve operating divisions. The Assistant ...
was tasked with implementing an annual survey to collect information on
morbidities A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...
– physical or mental conditions related to any
illness A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...
or injury – and medical service and
medical facility A health facility is, in general, any location where healthcare is provided. Health facilities range from small clinics and doctor's offices to urgent care centers and large hospitals with elaborate emergency rooms and trauma centers. The numbe ...
utilization. The most recent re-design of the survey
questionnaire A questionnaire is a research instrument that consists of a set of questions (or other types of prompts) for the purpose of gathering information from respondents through survey or statistical study. A research questionnaire is typically a mix of ...
was implemented in 1997.


Research topics

NHIS data contain information on
health Health, according to the World Health Organization, is "a state of complete physical, mental and social well-being and not merely the absence of disease and infirmity".World Health Organization. (2006)''Constitution of the World Health Organiza ...
, influences on health, and health outcomes, as well as common demographic indicators to give users the ability to examine health status, behavior, and
risk factors In epidemiology, a risk factor or determinant is a variable associated with an increased risk of disease or infection. Due to a lack of harmonization across disciplines, determinant, in its more widely accepted scientific meaning, is often use ...
within and across subsets of the population (such as racial and ethnic
health disparities Health equity arises from access to the social determinants of health, specifically from wealth, power and prestige. Individuals who have consistently been deprived of these three determinants are significantly disadvantaged from health inequiti ...
). The major health topics covered in the Core questionnaires include health status, insurance coverage,
complementary and alternative medicine Alternative medicine is any practice that aims to achieve the healing effects of medicine despite lacking biological plausibility, testability, repeatability, or evidence from clinical trials. Complementary medicine (CM), complementary and al ...
, use of health services,
immunizations Immunization, or immunisation, is the process by which an individual's immune system becomes fortified against an infectious agent (known as the immunogen). When this system is exposed to molecules that are foreign to the body, called ''non-se ...
, health behaviors,
injuries An injury is any physiological damage to living tissue caused by immediate physical stress. An injury can occur intentionally or unintentionally and may be caused by blunt trauma, penetrating trauma, burning, toxic exposure, asphyxiation, or o ...
,
occupational health Occupational safety and health (OSH), also commonly referred to as occupational health and safety (OHS), occupational health, or occupational safety, is a multidisciplinary field concerned with the safety, health, and welfare of people at wor ...
,
cancer screening Cancer screening aims to detect cancer before symptoms appear. This may involve blood tests, urine tests, DNA tests, other tests, or medical imaging. The benefits of screening in terms of cancer prevention, early detection and subsequent treatment ...
, ability to perform daily activities, and conditions such as
asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, co ...
,
diabetes Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ...
,
mental health Mental health encompasses emotional, psychological, and social well-being, influencing cognition, perception, and behavior. It likewise determines how an individual handles stress, interpersonal relationships, and decision-making. Mental hea ...
. NCHS continually produces chart books, statistical briefs, and fact sheets using NHIS data which shed light on these various facets of
morbidities A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...
and how the American populace behaves in response. Periodically, the NHIS includes supplemental questionnaires regarding a focused topic that might be of particular current interest. For example, a
cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
supplement was fielded in 1987, 1992, 2000, 2003, 2005, 2008, and 2010, and sponsored by the
National Cancer Institute The National Cancer Institute (NCI) coordinates the United States National Cancer Program and is part of the National Institutes of Health (NIH), which is one of eleven agencies that are part of the U.S. Department of Health and Human Services. ...
and th
National Center for Chronic Disease Prevention
This supplement included questions about
cancer screening Cancer screening aims to detect cancer before symptoms appear. This may involve blood tests, urine tests, DNA tests, other tests, or medical imaging. The benefits of screening in terms of cancer prevention, early detection and subsequent treatment ...
s,
diet Diet may refer to: Food * Diet (nutrition), the sum of the food consumed by an organism or group * Dieting, the deliberate selection of food to control body weight or nutrient intake ** Diet food, foods that aid in creating a diet for weight loss ...
, exercise, smoking, sun exposure, and
family history Genealogy () is the study of families, family history, and the tracing of their lineages. Genealogists use oral interviews, historical records, genetic analysis, and other records to obtain information about a family and to demonstrate kin ...
. Occupational supplement were fielded in 2010 and 2015, and sponsored by the
National Institute for Occupational Safety and Health The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the C ...
(NIOSH). These supplement included questions about work-related health conditions, work organization factors, and occupational psychosocial and physical/chemical exposures. A full list of supplements can be found on th
NHIS website


Publications

The National Health Interview Survey is commonly the subject of analysis in articles on health status and health behaviors in research journals such as Obesity, Journal of the American Dietetic Association, Health Services Research, and the American Journal of Public Health. A number of CDC reports, includin
Healthy People
rely on NHIS to monitor health estimates. The Department of Health and Human Services (HHS), Office of the Assistant Secretary for Planning and Evaluation (ASPE) tracks health insurance coverage in the United States using the NHIS. The National Center for Health Statistics publishes periodical statistical summaries, compiling the results of the most recent NHIS and trending those statistics over time for certain groups. NCHS/CDC also publish statistical reports on current topics of interest, and shorter data briefs. For example, NIOSH has published several peer-reviewed journal articles from the 2010 and 2015 NHIS Occupational Health Supplement results.


Methodology


Survey design

Noninstitutional civilian Americans (both citizens and non-citizens) are sampled by
household A household consists of two or more persons who live in the same dwelling. It may be of a single family or another type of person group. The household is the basic unit of analysis in many social, microeconomic and government models, and is i ...
, allowing for analysis of medical behavior at the familial-level. After a household has been sampled, one adult and one child (if any are present) is selected to complete the Sample Adult and Sample Child components of the survey. In years without budget cuts, approximately 35,000 households containing 87,500 individuals are included. NHIS follows a multi-stage area probability design, meaning that geographic areas – rather than unique households – are sampled first, and then within those selected areas, residences are sampled. Unlike surveys with a panel or longitudinal design, the entirety of data collected from each household occurs from a single interview lasting about an hour. The complex survey design must be analyzed with software capable of handling survey data that was not obtained from a
simple random sample In statistics, a simple random sample (or SRS) is a subset of individuals (a sample) chosen from a larger set (a population) in which a subset of individuals are chosen randomly, all with the same probability. It is a process of selecting a sample ...
, such as R, SUDAAN, SAS, Stata,
SPSS SPSS Statistics is a statistical software suite developed by IBM for data management, advanced analytics, multivariate analysis, business intelligence, and criminal investigation. Long produced by SPSS Inc., it was acquired by IBM in 2009. C ...
, and VPLX. In addition to appropriately weighting households that might have been over-represented in the raw data (due to oversampling of populations of interest), survey analysis packages are needed to employ the Taylor-series linearization technique to correctly calculate the
standard error The standard error (SE) of a statistic (usually an estimate of a parameter) is the standard deviation of its sampling distribution or an estimate of that standard deviation. If the statistic is the sample mean, it is called the standard error o ...
s and confidence intervals.


Linkage to other health surveys

The
Medical Expenditure Panel Survey The Medical Expenditure Panel Survey (MEPS) is a family of surveys intended to provide nationally representative estimates of health expenditure, utilization, payment sources, health status, and health insurance coverage among the noninstitutionali ...
currently uses the NHIS sampled population to form its own sampling frame (ultimately sampling one-half of NHIS respondent households for its own publicly available complete survey). After filling out a confidentiality agreement, AHRQ provides a crosswalk to merge these data. NHIS data can also be linked to death certificates in th
National Death Index (NDI)


Data Available

NHIS data are freely downloadable by the public, and generally become available in June or July for the preceding year's data set. Certain variables that might make survey respondents easily identifiable (such as geographic locations, exact dates of events and procedures) are not available from the publicly available data, but can be accessed and analyzed by applying for access to the NCH
Research Data Center
The current publicly available annual National Health Interview Survey data release consists of four files which describe the demographics and health-related characteristics of the survey population at the household, family, and person-level, as well as two files designed to capture information on any injuries experienced during the year.


Core


Household File

With one record per household in the sample, this file mainly contains descriptors necessary to determine the number of individuals and families within each sampled household, and allows researchers to link families or other unrelated individuals captured in any of the other Core files based on household of residence (using the HHX variable). This file also contains basic information on non-response and a household-level final weight.


Family File

This file contains one record per family in the sample, with general information on identifiers (such as family member age, race, family structure, family income), health status and limitations, injuries and poisonings, access to care and utilization, and health insurance. The family file can be linked to other files containing information on adults and children within each family (using the HHX and FMX variables).


Person File

This file contains information on every individual within every family within every household selected for participation in the NHIS. Survey data about individuals who were either not available at the time of the interview or under 18 were provided by an available adult in the household. This person-level file contains information on health status and limitation of activity, health care access and utilization, health insurance, socio-demographics, and income and assets. Examining this file using the final weight variable (WTFA) generalizes to the entire noninstitutional, civilian United States population.


Sample Adult and Sample Child Files

These two files contain information obtained from the survey response of one adult and one child (if one exists) sampled from each family contained in the family file, and can be linked up to household and family information (using the HHX and FMX variables). These two sample person files contain much more in-depth information about health conditions, physical and mental health status, health limitations, behaviors, and utilization than the family file. Their question topics are specific to either adults or children, but not both (such as occupational demographic questions in the adult file and childhood immunization questions in the child file). Much like the Person file, these two files can be used to create national estimates of all adults and children in the United States (using WTFA_SA to generalize to all adults and WTFA_SC to generalize to all children). Individuals can be matched between the Person and Sample Adult/Child files using the HHX (household), FMX (family), and FPX (person) fields.


Injury and Poisoning Files

The Injury and Poisoning Episode file contains event-level information about any injury event experienced by an individual within the household in the three months leading up to the interview. For each reported injury or poisoning event, a number of questions examining the severity and effect of the event were asked, such as whether a physician was consulted and what kind of injury was experienced. This episode file can be used to generalize about the frequency of all injuries experienced by Americans over a defined window of time. The final weight (WTFA) generalizes to the number of injuries that occur among the U.S. population. This file can be merged on to any of the other data files using the HHX (household), FMX (family), and FPX (person) merge fields. The Injury and Poisoning Verbatim file contains un-categorized, open-ended data provided by the respondent. This file can be linked to the cleaned Episode file using the HHX, FMX, FPX, and IPEPNO (Injury/Poisoning Episode Number) fields.


Supplemental

Supplemental data are available whenever funding and sponsorship allow. The topics of non-core questionnaires generally relate to a matter of current importance to policymakers or the research community. Occupational Health Supplement In 2010 and 2015, supplemental data were collected that relate to the impacts of work on health. Known as the Occupational Health Supplements, these data are available to chart using the Worker Health Charts tool. Worker Health Charts is a tool NIOSH uses to allow the public to visualize NHIS data, along with other work-related data sources. See the CDC Feature on Worker Health Charts and the NIOSH Science Blog to learn more about the tool and how it works.


See also

*
List of household surveys in the United States This is a list of surveys of households in the United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North Amer ...


References


External links

* {{Official website, https://www.cdc.gov/nchs/nhis/index.htm Demographics of the United States Health economics Health surveys Centers for Disease Control and Prevention