Major changes in data collection technology
- From 1963 through 1996, the NHIS questionnaire was printed as a paper booklet. The interviewer read the questions and wrote the answers in the booklet. Results were subsequently keyed into a computer in preparation for data processing.
- From 1997 through 2003, the NHIS used CASES software for computer-assisted personal interviewing (CAPI). The interviewer read the questions from a laptop screen and entered the responses directly into the laptop.
- In 2004, the NHIS CASES software was replaced by BLAISE CAPI software. This technology continues to the present.
Major changes in physical activity questions
- In 1975, questions on leisure-time physical activity were first introduced in the NHIS as part of a special topic supplement.
- In 1985, the NHIS became the federal government's tool for monitoring progress toward National Health Objectives for Physical Activity. A set of questions about more than 22 leisure-time sports activities, including frequency, duration, and intensity of each activity during the past 2 weeks, was included in supplements variously titled "Health Promotion and Disease Prevention" and "Healthy People" that were fielded in 1985, 1990, 1991, 1995, and 1998.
- In 1997, questions on usual leisure-time physical activity were first included in the NHIS annual core questionnaire, in the Sample Adult component. These questions have remained unchanged since mid-year 1997.
- In 1998, the NHIS questionnaire included both the 2-week sports activity questions (in the Healthy People supplement questionnaire) and the usual leisure-time physical activity questions (in the annual Sample Adult core questionnaire). Both sets of questions were asked of the same sample adult respondents in the same interview. For a comparison of these two physical activity measures, see Comparison of Two Sets of Physical Activity Questions.