Codes and Frequencies
Description
EMPHYSEMYRC indicates whether the person had chronic emphysema in the past year. This variable is created with supplemental programming by the IPUMS NHIS staff from the pre-1997 condition records. For general information about IHIS variables (such as EMPHYSEMYRC) created from the pre-1997 condition records, see the User Note on Condition Records and Condition Variables.
Defining Emphysema Records and Identifying Persons with Emphysema
For all available years, persons who were asked a direct question about emphysema and who have a chronic emphysema condition record are given a "Yes" code for EMPHYSEMYRC. Persons who were asked a direct question about emphysema but do not have a chronic emphysema record are given a code of "No." Persons who were not asked a direct question about emphysema, or for whom it is unknown whether they were asked such a question, are given a code of "NIU" (not in universe), regardless of whether they have a chronic emphysema record.
For 1970 and 1978, emphysema records were defined as those condition records with a code of "152" ("Emphysema") in the variable DIAGR1 in the original NHIS public use files. This condition code value comes from NCHS's Diagnostic Recode #1: Diseases, Injuries, and Impairments, not from the International Classification of Diseases (ICD) codes. Additionally, to be considered "chronic," emphysema condition records must have a code of "1" ("Chronic") in the variable CACODE in the original NHIS public use files.
For 1979-1981, chronic emphysema records were defined as those condition records with a code of "23" ("Emphysema") in the variable DIAGR3 in the original NHIS public use files. This condition code value comes from NCHS's Diagnostic Recode #3: Chronic Diseases and Impairments.
For 1982-1996, chronic emphysema records were defined as those condition records with a code of "609" ("Emphysema") in the variable C1CONDRC in the original NHIS public use files. This condition code value comes from NCHS's Diagnostic Recode C: Chronic Conditions and Impairments.
Weights
For 1970, EMPHYSEMYRC should be weighted with PERWEIGHT.
For 1978 to 1996, EMPHYSEMYRC should be weighted with CONDWT6.
Related Emphysema Variables
The nearest equivalent of EMPHYSEMYRC for 1997 forward is EMPHYSEMEV (Ever told had emphysema). However, researchers should use caution when comparing prevalence estimates derived from these two variables, as both the manner of collecting information about emphysema and the reference period differ greatly between the two. EMPHYSEMYRC was created by recoding condition records that were generated in response to several different survey questions about health problems underlying disability, sick days, or contacts with health care practitioners in the past year. EMPHYSEMEV, by contrast, is based on a direct question about whether the person ever had the condition emphysema.
Comparability
As with all of the person-level condition variables created by IHIS from condition records prior to 1997, the universe for EMPHYSEMYRC is substantially different for 1978 forward than it is for years prior to 1978. Beginning in 1978, only persons living in 1/6 of households, rather than all persons, were asked a direct question about having emphysema in the past year. This change requires that different weight variables be used depending on which years of data are analyzed. See the "Description" tab for details.
Additionally, there is a change in the way "Yes" responses are coded over time. See the User Note on Condition Records and Condition Variables for details about the composite coding scheme employed by IHIS.
Universe
- 1970: All persons.
- 1978-1996: Persons living in 1/6 of households (who received Condition List 6).
Availability
- 1970, 1978-1996
