Codes and Frequencies
KIDNYSTONYRC indicates whether the person had chronic kidney stones 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 KIDNYSTONYRC) created from the pre-1997 condition records, see the User Note on Condition Records and Condition Variables.
Defining Kidney Stone Records and Identifying Persons with Kidney Stones
For all available years, persons who were asked a direct question about kidney stones and who have a chronic kidney stones condition record are given a "Yes" code for KIDNYSTONYRC. Persons who were asked a direct question about kidney stones but do not have a chronic kidney stones record are given a code of "No." Persons who were not asked a direct question about kidney stones, 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 kidney stones record.
1973 and 1978-1981
For 1975 and 1978-1981, kidney stones records were defined as those condition records with a code of "182" ("Calculus of kidney and ureter") 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," kidney stones condition records must have a code of "1" ("Chronic") in the variable CACODE in the original NHIS public use files.
1982 to 1996
For 1982-1996, chronic kidney stones records were defined as those condition records with a code of "409" ("Kidney stones") in the variable C1CONDRC in the original NHIS public use files.
For 1973, KIDNYSTONYRC should be weighted with PERWEIGHT.
For 1978 to 1981, KIDNYSTONYRC should be weighted with CONDWT3.
For 1982 to 1996, KIDNYSTONYRC should be weighted with CONDWT4.
Related Kidney stones Variables
The nearest equivalent of KIDNYSTONYRC available after 1996 is KIDNYSTONYR (Told had kidney stones, past 12 months). However, researchers should use caution when comparing prevalence estimates derived from these two variables, as the manner of collecting information about kidney stones differs greatly between the two. KIDNYSTONYRC 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. KIDNYSTONYR, by contrast, is based on a direct question about whether the person had the condition kidney stones.
As with all of the person-level condition variables created by IHIS from condition records prior to 1997, the universe for KIDNYSTONYRC 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 kidney stones in the past year. 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.
- 1973: All persons.
- 1978-1981: Persons living in 1/6 of households (who received Condition List 3).
- 1982-1996: Persons living in 1/6 of households (who received Condition List 4).
- 1973, 1978-1996