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Duration of functionally limiting 2nd unclassified cause: Months

Codes and Frequencies

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For Sample Adults age 18+ who, without using special equipment, had any difficulty with one or more functional activities (FLANY), and who identified a second problem, not listed on the interviewer-provided flashcard and not one of the other categories available to interviewers for purposes of classifying conditions as a cause of any functional activity limitation (FLNEC2), FLNEC2MO reports the duration, in months, of the "not elsewhere classified condition".

Data on the duration of a limiting "not elsewhere classified condition" were collected via the question, "How long have you had [condition]?" Respondents could answer this open-ended question using the time unit of their choice (i.e., days, weeks, months, years, or since birth). The original responses to the question are reported in two complementary variables, FLNEC2TP (which specifies the time unit) and FLNEC2NO (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 (FLNEC2Y) and groups of months (FLNEC2MO).

The 1997 forward NHIS Survey Descriptions caution that because the ad hoc classified condition categories (such as a "not elsewhere classified condition" (FLNEC2)) were not included on flashcards given to respondents during the course of the interview, it is possible that weighted frequencies for these conditions may be underestimated. Thus, the NCHS recommends that "these variables should be analyzed with care."


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


All "unknown" cases for this variable share a common first digit of "9." The meaning of the second digit following the 9 differs for 2001 versus 2002 forward. In the earlier period, the "unknowns" were categorized as:

  • Unknown number of days (IPUMS NHIS code 91)
  • Unknown number of weeks (IHIS code 92)
  • Unknown number of months (IHIS code 93)
  • Unknown number of years (IHIS code 94)
  • Unknown time with condition (IHIS code 95)

In the latter period, "unknowns" were categorized as:

  • Unknown-refused (IHIS code 97)
  • Unknown-not ascertained (IHIS code 98)
  • Unknown-don't know (IHIS code 99)

Analysts can achieve comparability across all years by combining codes with a common first digit of 9 into a single "unknown" category.


  • 1997-1998; 2000-2018: Sample adults age 18+ who have difficulty with activities due to second unclassified problem.


  • 1997-1998, 2000-2018