Age Variable Definitions🔗

This page defines how age is represented for the child and birth parent across HBCD datasets.

Basic Demographics🔗

The Basic Demographics table contains global, static variables derived across administrative and instrument data. Age variables include the child's Gestational Age at Delivery as well as age variables specific to the birth parent, including Maternal Age at V01 and Maternal Age at Delivery. See documentation under Basic Demographics for details.

Tabulated Instrument & File-Based Data🔗

All variables below refer to the child and describe the child’s age at either:

• Instrument administration for tabulated instrument data
• Time of scan/data acquisition for file-based data (MR, EEG, and biosensor data, provided within session- and scan-level metadata files)

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V01 = Available Visit 1 only (prenatal)      V02+ = Available Visit 2 onward (post-birth)

TABULATED DATA🔗

Variable Name	Variable Label	Description	Visit
Gestational Age at Administration	gestational_age	Number of weeks (rounded down) between LMPFirst day of the birth parent's last menstrual period, estimated as EDD − 280 days and the V01 administration date May vary by ≤4 weeks across protocol elements (except for protocol exceptions)	V01
Chronological Age at Administration	candidate_age	Age in years (3 decimal places) at administration Calculated as: total elapsed days (rounded down) ÷ 365.25 Based on a jittered DOB (±7 days) to protect participant privacy	V02+
Adjusted Chronological Age at Administration	adjusted_age	Number of weeks (rounded down) between EDDEstimated Date of Delivery and the administration date Aligns preterm and full-term infants to a common developmental reference  Note: May be negative if collected prior to the EDD	V02+

FILE-BASED DATA🔗

Variable Name	Variable Label	Description	Visit
Adjusted Age at Time of Scan	age_adjusted	Time in days between EDDEstimated Date of Delivery and the acquisition date	V02+
Chronological Age at Time of Scan	age	Age in years (3 decimal places) at acquisition Calculated as: total elapsed days (rounded down) ÷ 365.25 Based on a jittered DOB (±7 days) to protect participant privacy	V02+