ENVIRONMENTAL HEALTH SUPPLEMENT NOTES 1. An Environmental Health record exists for every person in the NHIS 1991 completed basic (core) interview sample, regardless of age. 2. Three topics were addressed in the 1991 NHIS Environmental Health Questionnaire- 1) exposure to household smoke, 2) testing for lead content of paint in homes built before 1950 and 3) testing air in homes for Radon. This data file contains data for topics 1 and 2 only. The Radon items are not included as a result of a mid-year change in the NHIS' data collection procedures. Information obtained about Radon testing is available in the 1991 Health Promotion and Disease Prevention Public Use Data File. For NHIS' 1991 Quarters 1 and 2, the NHIS household respondent answered the Environmental Health questions. This person was initially designated as the respondent for this section of the NHIS questionnaire since it was thought they would be most knowledgable about Radon and its presence in the home. A review of completed NHIS questionnaires after data collection began however, revealed that household respondents rarely had heard of Radon. Since this initial knowledge question subsequently screened respondents from answering all remaining questions about Radon on the questionnaire, the little information on this subject that was being obtained in the NHIS could not be used to produce national estimates under the existing procedure. Therefore, in Quarters 3 and 4 the designated respondent for the Environmental Health questions became a randomly selected adult family member (i.e., the sample person). This change was necessary in order to produce national estimates on Radon knowlege. Even by designating the adult sample person as the Environmental Health respondent in Quarters 3 and 4, subsequent Radon analysis is limited. For analysis, the target population is those with knowledge of Radon. With few sample persons with knowledge of Radon, the utility of data collected from these Radon questions is limited. In addition, limiting these data to a 6-month data collection period further reduces the sample size for useful subdomain analysis. 3. For the Environmental Health questions, two types of item non-response are identified. (1) "Not ascertained" codes (usually code 8) include blanks when there should have been a response or when an impossible code appeared. - 1 - (2) "Unknown" codes (code 9) include responses of "don't know," or "refused" when the question was asked. 4. The response rate for the 1991 Environmental Health questions was 92.9. This response rate was calculated as follows: Household response rate from core (95.8 percent) multiplied by the Environmental Health response rate (97.0) = 92.9 percent 5. The Environmental Health data file consists of: a. The NHIS person record from the core questionnaire (locations 1-200). b. Weight fields (locations 201-215). c. The special topic data (locations 336-340). 6. Weights and Variances: Since the NHIS uses a multistage sample design to represent the civilian, non-institutionalized population of the United States, weights must be used to make accurate national estimates based on data from the National Health Interview Survey. Two weights are included on the 1991 Environmental Health data file: a. The Final Annual Basic Weight (location 207-215), calculated for each person in the NHIS sample, is the weight that will be used in most analyses of the Environmental Health data. This weight is the functional equivalent of the Annual Final Basic Weight found on the NHIS Person Record of the Basic Health and Demographic component of the survey (i.e., the Core questionnaire). The Environmental Health Final Annual Basic Weight differs from that calculated for the Core data file in that the weight field on the core data file is in binary format and the weight field on this file is in character format. b. The Interim Basic Weight (before age-sex-race adjustment), required by some software packages for variance estimation for surveys with complex sample designs, is also included on the data file (loc. 201- 206). - 2 - There are a number of computer programs that yield variance estimates for data based on complex sample surveys. Some are based on replication approaches and others are based on Taylor linearization approaches. In addition to the Interim Basic Weight (which is the weight prior to poststratification), included on the Environmental Health file is the full sample stratum identifier (loc. 179-181), the pseudo primary sampling unit (PSU) codes (loc. 187- 189), and the type of PSU (loc. 185) to permit the analyst the capability of using such variance estimation procedures. These variables and weights are necessary for directly calculating sampling variances. 7. Estimating numbers of events or conditions a. To reduce respondent error, the recall period for questions about some events is limited to two weeks. These events are: bed days and other restricted activity days, work loss and school loss days, and doctor visits. The two-week variables are found in locations 98-107 and 120-121. Estimates of the total number of occurrences of these events in the population can be derived as follows: Number of events x 26 (number of two-week periods in a year) x Final Annual Basic Weight = Total number of events occurring in the population during the data year, i.e. 1991. Example: Number of bed days (loc. 100-101) x 26 x Final Anual Basic Weight (loc. 207-215) = total number of bed days reported for the population in 1991. b. The recall period for acute incidence conditions is also two weeks and an annual estimate of the total number of acute incidence conditions is calculated using the same procedures as for two-week events: Number of acute incidence conditions x 26 x Final Annual Basic Weight = Total number of acute incidence conditions occurring in the population during 1991. Note: An acute incidence condition is an acute condition with onset during the two weeks preceding the date of interview. - 3 - c. The recall period for information on hospitalizations is 12 months. However, in calculating number of discharges and number of days in hospital (locations 132-141), only discharges occurring in the past 6 months are counted. Therefore, the weighted estimates for these events must be calculated as follows: (1) Number of discharges x 2 (number of 6-month periods in a year) x Final Annual Basic Weight = Total number of discharges occurring in the population in one year. (2) Number of days in hospital associated with discharges occurring in the past 6 months x 2 (number of 6-month periods in a year) x Final Annual Basic Weight = Total number of days of hospitalization occurring in the population in one year. 8. Calculation of rates for events and conditions: The number of events or conditions estimated for the population, as described in item 7 above, can be used as the basis for calculating rates of occurrence of these events (or conditions) per person and per 100 persons for the total U.S. population and for various population subgroups. Note: Only rates can be estimated from these data. The percent of the population experiencing a particular type of event during the data year cannot be estimated. [The percent of the population experiencing the event in the reporting period (i.e. two weeks or 6 months) can be estimated but is generally not meaningful.] 9. Data on hospital episodes and days, based on a 12-month recall are locations 122-131. The Final Annual Basic Weight is used for calculating estimates of these events in the same way it is used for all other person-based variables. These variables do permit estimating the percent of the population experiencing a hospital episode in the past year and the percent of the population having a specified number of hospital days. - 4 -