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Duration of limiting birth defect: Years

Codes and Frequencies

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For persons who have at least one activity limitation (LANY), and for whom a birth defect was reported as a condition causing any activity limitation (CLIMBIRTH), CLIMBIRTHY reports the duration, in years, of the birth defect.

Data on the duration of limiting birth defect were collected via the question, "How long [have/has] [you/person] had [a birth defect]?" Respondents could answer this open-ended question using the time unit of their choice (i.e., days, weeks, months, or years). The original responses to the question are reported in two complementary variables, CLIMBIRTHTP (which specifies the time unit) and CLIMBIRTHNO (which reports the number of such units). For the NHIS public use files, the National Center for Health Statistics (NCHS) recoded the results from these two variables to create two other variables using standard time units: years (CLIMBIRTHY) and groups of months (CLIMBIRTHMO).


Apart from a change in the coding of "unknown" cases, this variable is comparable across years.


In 2002 forward, the unknowns were categorized as:

  • Unknown number of years (IPUMS NHIS code 96)
  • Unknown-refused (IHIS code 97)
  • Unknown-not ascertained (IHIS code 98)
  • Unknown-don't know (IHIS code 99)

However, in 1997-2001, the category of "Unknown number of years" did not occur.

Analysts can achieve comparability across all years by combining two-digit codes for 96 forward into a single "unknown" category.


  • 1997-2018: Persons limited due to birth defect.


  • 1997-2018