Codes and Frequencies
For person who reported being hospitalized overnight during the previous year (HOSPNGHTD), HOSPNUMD reports the number of different times the person was in a hospital overnight during that period.
HOSPNUMD is a generated variable, which comes from hospital records constructed by NCHS, based on responses to questions about whether the person had been hospitalized, how many times hospitalized, and the dates of those hospitalizations. The basic question directly associated with HOSPNUMD was, "How many times was -- in a hospital since [date] a year ago?" (for 1969-1981) or "How many different times did -- stay in any hospital overnight or longer since [date] a year ago?" (1982 forward).
As is discussed in detail in the variable description for HOSPNGHTD, interviewers received detailed and largely consistent directions on what should count as an overnight hospital stay. For example, time in an emergency room, keeping a hospitalized family member company, and hospital admissions in which the person was released on the same date did not count as overnight hospital stays reported in HOSPNUMD.
HOSPNUMD is comparable for the period from 1969 to 1981, and again for the period 1982 to 1996. However, changes instituted in 1983 somewhat limit comparability between these two periods.
First, beginning in 1982, the question wording for HOSPNUMD changed from "How many times was -- in a hospital since [date] a year ago?" to "How many different times did -- stay in any hospital overnight or longer since [date] a year ago?"
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.
HOSPNUMD is substantively similar to the HOSPNUM variable available for 1997 forward. Question wording for HOSPNUM is the same as HOSPNUMD's question wording for 1982-1996, and the directions given to interviewers about what constituted an overnight hospital stay was largely consistent for 1969 forward.
There are, however, some differences before and after 1997 in how information was collected on the number of overnight hospital stays.
For example, for the period prior to 1997, the survey included follow-up verification questions to ensure that hospital stays for mothers and babies that were tied to deliveries were counted as hospital nights. Furthermore, HOSPNUM is based directly on answers from respondents; HOSPNUMD results derive from hospital records generated at NCHS, with the data source having to pass certain quality checks, such as adequate information on hospitalization dates. For these reasons, researchers should exercise caution in comparing pre-1997 results from HOSPNUMD with post-1997 results from HOSPNUM.
As the 1997 NHIS Survey Description, states:
- 1963-1996: All persons.
- 1963-1996 : PERWEIGHT