National Health Interview Survey
Health Measures in the 1997 Redesigned National Health Interview Survey (NHIS)
This document describes the general health measures included in the Redesigned NHIS Basic Module starting in January 1997. Information in the Family Core questionnaire is collected on all household members. A household adult reports information for a randomly selected child less than 18 years of age in the Child Core questionnaire, and a randomly selected adult reports for him/herself in the Adult Core questionnaire.
Questions in this section are designed to retain comparability to previous NHIS surveys for reporting of activity limitation due to physical, mental, or emotional problems. Information on activity limitation is collected on each family member, and is based on questions that ask about the need for assistance with personal care needs such as eating, bathing, dressing or getting around, or assistance handling routine needs such as everyday household chores, doing necessary business, shopping or getting around for other purposes. If any limitations are identified, the respondents are asked to specify the health condition causing the limitation and indicate how long they have had the condition. Since cognitive impairment is increasingly recognized as a source of activity limitation among older adults, a new question has been added to determine if anyone in the family is limited because of difficulty remembering or periods of confusion. Other new measures in this section include determining if any family members have difficulty walking without any special equipment and identifying children who receive Special Education or Early Intervention Services. At the end of this section, the general health status of each household member is reported as excellent, very good, good, fair, or poor.
Questions on limitation of activity in the Adult Core are used to determine the number of work-loss days and bed days reported during the 12 months prior to the interview. In addition, respondents are asked if their health is better, worse, or the same compared with 12 months ago. There are also nine Nagi items which attempt to measure physical functioning in a context that is not activity specific. The questions allow persons to report the degree of difficulty they experience doing activities such as walking 3 city blocks, standing for 2 hours, or lifting or carrying something as heavy as 10 pounds such as a bag of groceries. Respondent are also asked to rate the difficulty they experience in engaging in social activities and recreation.
Questions on limitation of activity in the Child Core are used to determine limitations in movement such as walking, running, or playing and whether or not the causal impairment is expected to last a year or more. Respondents are asked whether the child has a health problem that requires prescription medicine for a duration of 3 months or longer. This question is designed to assess chronicity of the health problem. Respondents are also asked if they had ever been told by a school official or health care provider that the child has a learning disability.
Questions in this section are designed to improve injury surveillance by asking about the external causes and circumstances of injury. Two screening questions capture injury and poisoning events that occurred in the 3 months prior to interview and required medical attention. The recall period was lengthened from 2 weeks (old NHIS) to 3 months in order to obtain larger numbers of events. Verbatim responses on how the injury happened, the kind of injury, and the body part or parts affected are recorded by the interviewers and are then coded to ICD 9-CM e-codes during data processing. Additional information related to activity and place of occurrence of the injury is being collected to be used in new external cause-of-injury groupings for reporting injury morbidity data.
The purpose of this section is to classify all household members by type of health care coverage. Information is provided by an adult knowledgeable about the family's health insurance, when available; else, information is collected from the family respondent. Questions are asked about who in the family is covered and the kind of coverage (private, Medicare, Medicaid, Military/Champus/Tricare, Indian Health Service, State-sponsored or government plan) he/she receives. When indicated, respondents are asked to provide the full names of the plans which are recorded verbatim by the interviewers. Plan names are coded into known types such as fee-for-service, HMO, PPO, POS, etc., during data processing by means of an updated list of U.S. health plans maintained by NCHS. Other information collected from respondents includes the source of coverage, i.e., the workplace or direct purchase, and the annual amount spent for health insurance premiums including payroll deductions. Information is also collected on noncovered household members on the length of time without coverage as well as the reasons that coverage stopped. The last question in the health insurance section asks respondents to estimate the annual household expenditure for medical care, including dental care.
Many of the questions in this section are derived from the 1993-1995 NHIS Access to Care supplements. Items in the family core assess the extent of access problems resulting from cost considerations. Questions on access in the Adult and Child cores are designed to identify persons who have a usual source of care and to determine the nature of that source. Respondents are also asked if this usual source is also the place where preventive care is received, or if it is received elsewhere. These questions are typical of usual source questions used in many access surveys. Persons are asked if they have recently changed their usual source(s) of care. In the past, respondents were asked to indicate a variety of reasons for such changes. In this survey, respondents are asked directly about reasons related to health insurance only. The last two questions identify persons who have delayed care for reasons other than costs (couldn't get through on the phone, couldn't get an appointment, etc.) and/or who have not gotten specific types of care that they needed (prescription medicines, mental health, or dental care).
The Family Core contains questions on hospitalizations that are used to monitor trends and differentials in inpatient stays and length of stay by sociodemographic, health status, and health insurance variables. Information on past 12 month hospitalizations including the total number of days hospitalized is collected for all family members. A question identifies hospitalization for childbirth that will allow analysts to exclude deliveries from estimates of hospital stays. The Family Core also contains questions on health care received in the 2 weeks prior to the interview. Respondents are asked whether they have received care of any kind from medical doctors or any other health professionals such as nurses, physical therapists, and chiropractors. Health care contacts are categorized by home visits, phone contacts, and office/clinic or ER visits.
Items in the Adult and Child core include questions on the length of time since last contact with 1) a dentist or 2) a doctor or other health care professional. Individuals report whether they have seen or talked to specific types or categories of health care providers during the 12 months prior to the interview. Categories of providers include mental health professionals, eye doctors, foot doctors, chiropractors, allied health professional such as physical therapist and speech therapists, and physician assistants or nurse practitioners. Respondents are also asked about the type of medical doctor seen during encounters in the 12 months prior to the interview. The purpose of these questions is to track the proportion of visits to generalists and to specialists. Additional information is collected on the number of health care provider visits in each of the following places in the 12 months prior to interview: hospital emergency room, home, and other places including physician offices. Information on the number of inpatient or outpatient surgeries during the 12 months prior to interview is also collected.
The section on health conditions was designed with the goals of substantially reducing the length of the NHIS survey and eliminating the analytic complexity of the data while preserving the ability to produce national estimates of disease prevalence. Questions that use to cover 133 conditions in six condition lists have been reduced to a single list consisting of several domains which are in the Adult and Child cores. The domains for adults are organized by organ system or health topic and include the following: cardiovascular disease, respiratory conditions, cancer, diabetes, gastrointestinal conditions, renal conditions, joint symptoms, oral health, sensory impairments, pain, and mental health. The mental health section consists of a brief symptom screening battery using a Likert scale with a 30 day reference period. General distress symptoms are known predictors of service utilization. There is also one question on the impact of these symptoms on a person’s activities to assess the severity of distress. Pain questions in the NHIS are designed to assess pain a person experienced in the 3 months prior to the interview. Respondents are asked about pain that lasted a whole day or more. Sample adults are asked about neck pain, back pain, facial ache, or pain and headaches/migraines.
Information on conditions are self-reported in the Adult Core and proxy reported in the Child Core. Questions on health conditions for children include those that are associated with disabilities such as cerebral palsy, mental retardation, Downs syndrome, among others; and those associated with learning disabilities such as Attention Deficit Disorder. Information is also collected on important childhood illnesses or impairments including, but not limited to, asthma, allergic conditions, ear infections, headaches/migraines, seizure disorders, hearing and visual impairments and stuttering. The redesigned NHIS also includes a brief child behavior scale, or mental health indicator. These questions are derived from the Child Behavior Check List. Items selected for inclusion were those that best discriminated between children referred for mental health care and those who were not. Specific sets of questions were developed for boys and girls by age groups.
Questions on health behaviors include tobacco use, physical activity, and alcohol use. They are in the Adult Core questionnaire.
The NHIS has long been an important part of national tobacco use surveillance. Questions have been designed to monitor self-reported cigarette smoking behavior. Respondents are asked if they ever smoked 100 cigarettes, and if so, the age at which they started smoking. Information on smoking behavior is collected to categorize respondents as former, current, or never smokers. Former smokers are asked to provide the length of time since quitting. Current smokers are asked about the average number of cigarettes smoked per day, and the number of days they smoked in the past month, and quit attempts.
A program of regular physical activity is known to prevent a number of chronic health conditions and enhance good health. Persons are asked about physical activities (exercise, sports, or physically active hobbies) that are done during leisure time. Respondents are asked about 2 levels of activity: 1) how often they do VIGOROUS activities lasting at least 10 minutes that cause heavy sweating or large increases in breathing or heart rate, 2) how often they do LIGHT or MODERATE activities that cause light sweating or slight to moderate increase in breathing or heart rate. Information on the duration of the activity is ascertained for each of these levels. In addition, respondents are asked how often they do physical activities designed to STRENGTHEN muscles such as lifting weights or doing calisthenics.
Questions are similar to previous NHIS items on self-reported alcohol use. Respondents are asked whether they have had at least 12 drinks in ANY ONE YEAR or in their ENTIRE LIFE. Persons reporting alcohol use are asked about consumption in the past year. Respondents are asked how often they drink, how much they drank on the days that they drank, and how many days in the past year they had 5 or more drinks.
Both the Adult and Child Core questionnaires contain questions on immunizations. The Adult questionnaire includes questions on receipt of a flu shot during the past 12 months and ever having a pneumonia vaccine. These items are used to track progress toward a national health objective for the year 2000, which is to increase pneumococcal and influenza vaccination levels to greater than or equal to 60 percent for persons at high risk for complications from these diseases, including older persons.
Questions in the Child Core are identical to those in previous NHIS Immunization Surveys, with the addition of new questions on chicken pox vaccination and adolescent immunizations. The NHIS has been an important part of the Childhood Immunization Initiative and is critical for monitoring vaccination coverage of 2 year old children. Information is collected from a knowledgeable adult about doses of DTP, Polio, MCV, Hib, Hep B, and Varicella given to sample children under 7 years of age as well as all 12-35 month old children in the household. This information is collected from a shot record, if available, or by history. Information on children 7-17 years old is obtained for the following antigens: MCV, Hep B, Varicella and Td (tetanus diphtheria booster). An ongoing National Immunization Provider Record Check Study is done in conjunction with the NHIS to adjust the estimates of vaccination coverage for children 12-35 months of age.
The NHIS has included questions on AIDS since 1987, with a primary focus on AIDS knowledge and attitudes from 1988 through 1995. As AIDS prevention programs have emphasized early detection and treatment of HIV infection, the 1997 NHIS questions are designed to monitor voluntary HIV counseling and testing. Respondents are asked about their blood donation history and about any tests they may have had for HIV infection exclusive of blood donation. Persons who have been tested for HIV are asked about the location of the test, the reason they were tested, whether or not they received the results of their tests, how the test results were received (by mail, telephone, or in person), and if they received counseling at the time they received their results. Respondents who indicate that they have not been tested are asked about any intentions to get tested in the next year, where they are likely to be tested, and the likely reason they would have the test. Two questions ask about self-perceived risk of infection, and whether or not any of a list of risk items applies to the respondent (including being a hemophiliac, having used IV drugs, and being a homosexual male).