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Was in a hospital overnight in past 12 months (pre-1997)

Codes and Frequencies

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HOSPNGHTD indicates whether the person was a patient in a hospital overnight during the past 12 months. This variable is a generated variable, which was constructed by the NCHS based on responses to questions on hospitalizations at two parts of the survey. In the first part, interviewers asked, "Was -- a patient in a hospital at any time since [a year ago]?" In the second part, interviewers asked, "How many different times was -- in a hospital since a year ago?" Responses to the second question are reported in HOSPNUMD.

If, earlier in the survey, any hospital visits during the previous two weeks were reported for the person, then that person was automatically assigned the response of "Yes" for HOSPNGHTD. In such a case, information was then collected on how many times the person was hospitalized in the past 12 months (HOSPNUMD).

Definition of Hospital and Reference Period 

For 1969-1981, nursing homes and convalescent homes were also considered hospitals, in the context of this question. In those years, separate verification questions for stays in nursing homes or convalescent homes were included, to ensure these stays were counted (so long as the person who had stayed in such an institution was a household member at the time of the interview). Hospitalizations for deliveries were also included, and interviewers probed to ensure that deliveries counted as (overnight) hospitalizations for both the mother and the baby.

The Field Representative's Manuals for 1969-1996 state that, for statistical purposes, the actual reference period for the hospitalizations reported in HOSPNGHTD is 13 to 14 months prior to the interview. For example, as the Manual for 1982 explains:

Although the survey is primarily concerned with hospitalizations which occurred during the past 12 months, for statistical purposes we also need to know about hospitalizations which started before the past 12 months in case they extended into the 12-month period. Therefore, the reference period used is a period of 13 to 14 months prior to the interview.

Definition of Patient 

The Field Representative's Manuals for 1969-1970 noted.

If a respondent should ask what is meant by 'being in a hospital,' explain that this means remaining overnight in a hospital as an inpatient for some illness condition, for childbirth, for an operation, etc. Going to an outpatient clinic in a hospital or to visit another person who is a patient there, should not be counted as 'being in a hospital.'

Similarly, the Manual for 1972 defined being a "patient" as being admitted and staying overnight or longer in a hospital, excluding the emergency room or outpatient clinic. (This definition was not routinely shared with respondents.) From 1982 forward, the Field Representative's Manuals also instructed interviewers to exclude "stays" in the hospital for nonmedical reasons, such as a parent staying with a sick child. Interviewers were directed to "not include stays in the hospital during which the person does not spend at least one night, even though surgery may have been performed," and also to exclude cases in which the person was admitted to and released from the hospital on the same date.

Collecting Information on Dates of Hospitalization 

Between 1969 and 1996, respondents were asked to report the exact dates, or their best estimate of the dates, for each hospitalization. Interviewers were instructed to probe to determine the dates as closely as possible. The Manuals urged, "Use the calendars and the list of holidays in your Flashcard Booklet to assist the respondent in recalling dates," and provided examples of appropriate probe questions (e.g., "Was it before or after Memorial Day (or some other holiday)?")

Considerable space was devoted to this issue, with the Manuals concluding:

If, after your additional probing, the respondent is still unable to give an exact date, determine whether it was the early, middle, or late part of the month; winter, spring, summer, or fall; or one of two months, such as May-June; or between two dates, such as June 6-June 10. For statistical purposes, a date must be entered for each hospital entry. It is essential that you obtain the maximum amount of information available, even if it is an estimated date. If necessary, schedule a telephone callback to obtain the date from a more knowledgeable respondent.

If adequate information about the date of the hospitalization was not provided (if, for example, the spaces for filling in month, date, and year of the hospitalization on the questionnaire were left blank), then no hospital record was generated for that stay was generated by NCHS.


From 1969 to 1981, the question wording for HOSPNGHTD remained unchanged (i.e., "Was -- a patient in a hospital at any time since [date] a year ago?")

1982 marked the inception of changes in how information was collected for HOSPNGHTD. First, the term "overnight" was added to the question for emphasis (i.e., "Since [date] a year ago, was -- a patient in a hospital OVERNIGHT?").

Second, probing questions about stays in nursing or convalescent homes were dropped in 1982.


For 1982, the survey text obliquely included nursing homes in the wording, "How many nights was -- in the hospital (nursing home)?," but the earlier follow-up questions about "Was anyone in the family in a nursing home, convalescent home, or similar place since [date] a year ago?" disappeared. From 1983 forward, the use of the parenthetical "nursing home" was removed from the survey question text. The effect of this change may be modest, for a note in the NCHS 1982 Current Estimates states, "Prior to 1982, few additional hospitalizations were in fact detected by this question." The shift may, however, result in a slight drop in the number of overnight hospital stays reported for older people after 1982.

Substantively, HOSPNGHTD is similar to the HOSPNGHT variable available for 1997 forward.
There are, however, some differences in how the information was collected for HOSPNGHTD (pre-1997) and HOSPNGHT (1997 forward).


For example, only the question wording for 1997 forward explicitly included the directive, "Do not include an overnight stay in the emergency room." Also, beginning in 1997, interviewers did not probe to include deliveries (although the Field Representatives Manuals prompted interviewers to "include new mothers and babies who were hospitalized for the baby's birth.") Further, HOSPNGHT is based directly on answers from respondents; HOSPNGHTD results derive from hospital records generated at NCHS, with the source data having to pass certain quality checks, such as adequate information on the date of the hospitalization. For these reasons, researchers should exercise caution in comparing pre-1997 results from HOSPNGHTD with post-1997 results from HOSPNGHT.

As the 1997 NHIS Survey Description, states:

Health care utilization estimates based on the 1997 NHIS may differ from those for earlier years of the NHIS due to changes in the questions and/or the context of the questions. Thus, 1997 estimates of health care utilization may not be comparable to estimates from previous years. ... Users are advised to compare 1997 NHIS questionnaire items pertaining to health care utilization to those used in previous NHIS surveys.


  • 1963-1996: All persons.


  • 1963-1996