National Health and Nutrition Examination Survey

The diabetes section (variable name prefix DIQ) provides personal interview data on diabetes, prediabetes, use of insulin or oral hypoglycemic medications, and diabetic retinopathy. It also provides self-reported information on awareness of risk factors for diabetes, general knowledge of diabetic complications, and medical or personal cares associated with diabetes.

All survey participants aged 1 year and older were eligible. The questions asked varied by age and history of diabetes. Please refer to the diabetes questionnaire and corresponding codebook for question-specific details about the eligible target group.

These questions were asked, in the home, by trained interviewers using the Computer-Assisted Personal Interview (CAPI) system. Hand cards showing response categories were also used for some questions. When necessary, household interviewers read the hand cards to survey participants. Participants 16 years of age and older and emancipated minors were interviewed directly. A proxy provided information for survey participants who were under 16 years of age and for participants who could not answer the questions themselves.

The CAPI system is programmed with built-in consistency checks to reduce data entry errors. CAPI also uses online help screens to assist interviewers in defining key terms used in the questionnaire.

Frequency counts were checked, “skip” patterns were verified, and the reasonableness of question responses was reviewed. Edits were made to some variables to ensure the completeness, consistency, and analytic usefulness of the data. Edits were also made, when necessary, to address data disclosure concerns.

DID040: How old when a doctor first told you that you had diabetes?
All responses of age 80 years and older are coded as “80”, to be consistent with the coding for the participant age variable in the demographics file. Also, the onset of diabetes at age less than 1 year was coded as 666.

DID060: For how long have you been taking insulin?
Taking insulin less than 1 month was coded as 666.

DIQ175A–DIQ175W: Why do you think you are at risk for diabetes/prediabetes?
The variables DIQ175A–DIQ175U correspond to each response category in the hand card. The variables DIQ175V (Craving for sweet/eating a lot of sugar), DIQ175W (Medication), and DIQ175X (Polycystic ovarian syndrome) were derived from other specified responses.

DID250: How many times have you seen doctor in the past 12 months?
The value was coded as 0 for participants who reported “None.”

DID260: How often do you check your blood for glucose or sugar?
This variable was coded as 0 for participants who reported “Never.”

DID320: What was your most recent LDL cholesterol number?
This variable was coded as 5555 and 6666 for participants who reported “Never heard of LDL” and “Never had cholesterol test” respectively.

DID310S/D: What does doctor say your blood pressure should be?
DID330: What does doctor say your LDL cholesterol should be?
If a participant reported “Provider did not specify goal,” the value of corresponding variable was coded as 6666.

DID341: During the past 12 months, how many times has a doctor checked your feet for any sores or irritations?
The value was coded as 0 for participants who reported “None.”

DID350: How often do you check your feet for sores or irritation?
The value was coded as 0 for participants who reported “None.”

In the 2015–2016 data, the core questions for the diabetes component, including doctor diagnosed diabetes, duration of diabetes, insulin use, oral diabetic medication, and diabetic retinopathy are similar to the 1999–2014 publicly release data. Questions about the participants’ knowledge of their own levels of A1c, blood pressure, and cholesterol and knowledge of appropriate target levels, as suggested by their physicians, are similar to the 2005–2008 and 2011–2014 public release data. The responses to these questions reflect the participants’ knowledge and may not be biologically reasonable. Questions regarding “Why participants feel they may be at risk for diabetes” were collected since the 2011–2012 survey.

When combining DIQ data from different survey cycles, please note that there is a possible name change for the same question across survey cycles due to data processing and editing. The following cross reference table shows these variable names from the 1999–2000 data through the 2015–2016 data.

Questions about whether the participant was told to control weight, increase physical activity, and reduce fat and whether the participant was now doing these activities are in the Medical Condition Section in the 2011–2016 surveys. 

The analysis of NHANES 2015–2016 diabetes questionnaire data must be conducted using the appropriate survey design variables, sample weights, and the basic demographic variables. Interview weights should only be used if questionnaire data are analyzed by themselves. However, if DIQ data are merged with the MEC examination data or laboratory data, the MEC examination weights should be used for analyses. If DIQ data are merged with laboratory sub-sample data, sub-sample weights should be used for analyses.

Please refer to the NHANES Analytic Guidelines and the on-line NHANES Tutorial for further details on the use of sample weights and other analytic issues.