Protocol - Current Age

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Protocol Name from Source:

National Health and Nutrition Examination Survey (NHANES), 2005-2006


Publicly available


The interviewer asks the respondent for his or her date of birth in MM/DD/YYYY format. If the respondent does not know his or her date of birth, the interviewer asks an alternative question to determine his or her age. NOTE: The current age of the respondent can be calculated, given the date of the interview.


What is your birthdate? MM/DD/YYYY;

[ ] 9 Don’t Know [ask follow-up question];

[ ] 7 Refused

[Follow-up question if "don’t know":] About how old are you? AGE _______;

[ ] 999 Don’t Know

[ ] 7 Refused

Personnel and Training Required

The interviewer must be trained to conduct personal interviews with individuals from the general population. The interviewer must be trained and found to be competent (i.e., tested by an expert) at the completion of personal interviews.* The interviewer should be trained to prompt respondents further if a "don’t know" response is provided.

* There are multiple modes to administer this question (e.g., paper-and-pencil and computer-assisted interviews).

Equipment Needs

While the source instrument was developed to be administered by computer, the PhenX Working Group acknowledges these questions can be administered in a noncomputerized format (i.e., paper-and-pencil instrument). Computer software is necessary to develop computer-assisted instruments. The interviewer will require a laptop computer or handheld computer to administer a computer-assisted questionnaire.


Requirement CategoryRequired
Average time of greater than 15 minutes in an unaffected individualNo
Major equipmentNo
Specialized requirements for biospecimen collectionNo
Specialized trainingNo

Mode of Administration

Life Stage:

Infant, Toddler, Child, Adolescent, Adult, Senior, All Ages, Pregnancy

Specific Instructions:

The question may be asked of a proxy. Proxies are others in the household who can answer on behalf of the index person (e.g., parent, spouse) if the index person is too young, incapacitated, deceased, or cannot be located.

Research Domain Information

Release Date:

May 31, 2016


Question to determine the respondent’s current age using his or her date of birth.


Current age is a critical component of a respondent’s demographic background. Date of birth (DOB)/current age is essential to medical research because it captures the age at the time of the clinical visit or diagnosis. Age is related to nearly all diseases and conditions and is the strongest potential confounder of other effects on these processes. Current age is often used to stratify respondents for more valid comparison (e.g., obesity of males aged 40-45 in Mississippi).

Selection Rationale

Age is a primary predictor of disease and the most important potential confounder in epidemiologic studies.

Age at date of interview or exam can be compared to age in future follow-up interviews or exams for longitudinal research purposes.

Vetted against several other current age questions, the National Health and Nutrition Examination Survey (NHANES) question was selected because it included the date of birth (DOB) and a follow-up question to collect current age if the respondent did not know his or her DOB.


English, Spanish


Common Data Elements (CDE)Birth Date2201154CDE Browser
Logical Observation Identifiers Names and Codes (LOINC)Current age proto62293-6LOINC

Process and Review

The [link[phenx.org/node/102|Expert Review Panel #2]] (ERP 2) reviewed the measures in the Demographics, Environmental Exposures, and Social Environments domains.

Guidance from ERP 2 includes:

• No significant changes to measure

Back-compatible: no changes to Data Dictionary

Previous version in Toolkit archive ([link[www.phenxtoolkit.org/index.php?pageLink=browse.archive.protocols&id=10000|link]])


National Center for Health Statistics. National Health and Nutrition Examination Survey (NHANES), Screener Module 1, 2005–2006. Question numbers: SCQ.290 and SCQ.292.

General References

Public Population Project in Genomics (P3G) Data Shaper.

Protocol ID:



Export Variables
Variable NameVariable IDVariable DescriptionVersiondbGaP Mapping
PX010101_Birthdate_DayPX010101010200What is your birthdate? Day4Variable Mapping
PX010101_Birthdate_YearPX010101010300What is your birthdate? Year4Variable Mapping
PX010101_Birthdate_CodedPX010101010400What is your birthdate?4N/A
PX010101_AgePX010101020000About how old are you?4Variable Mapping
PX010101_Age_CodedPX010101020100About how old are you?4N/A
PX010101_Birthdate_MonthPX010101010100What is your birthdate? Month4Variable Mapping