Codes and Frequencies
CATARACTNOWC indicates whether the person now has chronic cataracts. 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 CATARACTNOWC) created from the pre-1997 condition records, see the User Note on Condition Records and Condition Variables.
Defining Cataract Records and Identifying Persons with Cataracts
For all available years, persons who were asked a direct question about having cataracts and who have a chronic cataract condition record are given a "Yes" code for CATARACTNOWC. Persons who were asked a direct question about having cataracts but do not have a chronic cataract record are given a code of "No." Persons who were not asked a direct question about cataracts, 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 cataract record.
For 1971 and for 1977 to 1981, chronic cataract records were defined as those condition records with a code of "121" ("cataracts, all forms") 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," cataract records must have a code of "1" ("Chronic") in the variable CACODE in the original NHIS public use files.
For 1982 to 1996, chronic cataracts records were defined as those condition records with a code of "241" ("cataracts") 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 1971 and 1977, CATARACTNOWC should be weighted with PERWEIGHT.
For 1978 to 1981, CATARACTNOWC should be weighted with CONDWT4.
For 1982 to 1996, CATARACTNOWC should be weighted with CONDWT2.
Related Cataract Variables
The nearest equivalent of CATARACTNOWC available after 1996 is CATARACTNOW (Now have cataracts). However, researchers should use caution when comparing prevalence estimates derived from these two variables, as the manner of collecting information about cataracts differs greatly between the two. CATARACTNOWC 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. CATARACTNOW, by contrast, is based on a direct question about whether the person had cataracts.
As with all of the person-level condition variables created by IHIS from condition records prior to 1997, the universe for CATARACTNOWC 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 currently having cataracts. There is also a minor universe change between the sets of years 1978-1981 and 1982-1996. These changes require 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.
- 1971; 1977: All persons.
- 1978-1981: Persons living in 1/6 of households (who received Condition List 4).
- 1982-1996: Persons living in 1/6 of households (who received Condition List 2).
- 1971, 1977-1996