Codes and Frequencies
ASTHMAYRC indicates whether the person had chronic asthma 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 ASTHMAYRC) created from the pre-1997 condition records, see the User Note on Condition Records and Condition Variables.
Defining Asthma Records and Identifying Persons with Asthma
For all available years, persons who were asked a direct question about asthma and who have a chronic asthma condition record are given a "Yes" code for ASTHMAYRC. Persons who were asked a direct question about asthma but do not have a chronic asthma record are given a code of "No." Persons who were not asked a direct question about asthma, 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 asthma record.
For 1970 and 1978-1981, chronic asthma records were defined as those condition records with a code of "24" ("Asthma [with or without hay fever]") 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 asthma records were defined as those condition records with a code of "602" ("Asthma") 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.
For 1970, ASTHMAYRC should be weighted with PERWEIGHT.
For 1978 to 1996, ASTHMAYRC should be weighted with CONDWT6.
Related Asthma Variable
The nearest equivalent of ASTHMAYRC for 1997 forward is ASTHATAKYR (Had asthma attack/episode, past 12 months). However, researchers should use caution when comparing prevalence estimates derived from these two variables, as both the manner of collecting information about asthma differs greatly between the two. ASTHMAYRC 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. ASTHATAKYRC, by contrast, is based on a direct question about whether the person had an asthma attack or episode in the past year.
As with all of the person-level condition variables created by IHIS from condition records prior to 1997, the universe for ASTHMAYRC 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 asthma 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.
- 1970: All persons.
- 1978-1996: Persons living in 1/6 of households (who received Condition List 6).
- 1970, 1978-1996