NHIS Tracks Nation's Health, Household by Household
November 13, 2013
Day in and day out, almost continuously for more than 50 years—since before the formation of NCHS—the procedure has been the same. An interviewer for the National Health Interview Survey (NHIS) finds a household on the interview assignment list, approaches a resident, and, if all goes well, spends the next hour (more or less) collecting data that will contribute to a clear, accurate picture of the current state of the nation's health.
NHIS is the nation's largest in-person household health survey. NHIS first went into the field in July 1957 and has never looked back. Nowadays, several hundred full- and part-time interviewers, hired by the U.S. Census Bureau under contract with NCHS, fan out across the country to conduct NHIS interviews. Except for a few days of survey training near the beginning of each calendar year, interviewers are in the field continuously. The data they collect are designed to be representative of the civilian noninstitutionalized population of the United States and, after processing, are released to the public online once each year. The 2012 NHIS public-use files contain data for 108,131 people from 42,366 households.
Dr. Jane Gentleman, Director of the Division of Health Interview Statistics, says that people are sometimes surprised to hear that Census Bureau interviewers work on other surveys besides the decennial census. Actually, she says, the Census Bureau provides data collection and other survey operations for dozens of other surveys besides NHIS, including two other NCHS surveys. The relationship between NCHS and the Census Bureau is a notable example of close and productive collaboration between government agencies.
NHIS consists of two major components: the core and supplements. Core questions are relatively stable from year to year and cover topics including health status, utilization of health care services, health insurance, health-related behaviors (such as use of tobacco and alcohol), risk factors, and demographic and socioeconomic information. DHIS revises core questions when necessary to reflect changes in both the nation at large and the health care system. After a long number of years a thorough review and update of the entire NHIS questionnaire becomes appropriate; the last one occurred in 1997, and the next one is planned for 2017.
To complement the stable general health data provided by the NHIS core, a number of supplements are added to the questionnaire each year to collect topical, specialized information. These supplements are cosponsored on a cost-recovery basis by government agencies outside NCHS. For the 2012 survey, supplements included questions on balance, voice, speech and language (sponsored by the National Institute on Deafness and Other Communication Disorders, NIH), child mental health (Center for Mental Health Services, SAMHSA), tobacco (Center for Tobacco Products, FDA), and food security (USDA), among others.
The survey supplements are a perfect example of statistical synergy. NHIS data users can analyze the rich multivariate data provided every year by the ongoing comprehensive core questions, in combination with data from a supplement (and from other supplements to the NHIS in the same year). For example, Dr. Gentleman says that HHS' Healthy People Initiative uses data from both NHIS core questions and NHIS supplemental questions to monitor progress toward that program's objectives.
Looking ahead, the next redesign of the NHIS core is targeted for implementation in 2016. Meanwhile, Dr. Gentleman says that staff members are hard at work producing and analyzing NHIS data to monitor changes to the population's access to and utilization of health care as more provisions of the Affordable Care Act take effect. Also, an Online Analytic Real-time System is being developed to add to the various ways that researchers, policy makers, government and nongovernment programs, teachers, students, journalists, and the general public can obtain analyses of the ever-valuable NHIS data.