Understanding the harmonisation of LPS year of birth (age) variables#
Last modified: 03 Jul 2025
Introduction#
All LPS contributing to UK LLC have included information about their participants’ age, though this information is collected in a variety of ways:
Date of birth
Self-reported age at a given time point (e.g. completion of a questionnaire)
Self-reported age range (16-24, 25-49, etc.) at a given time point
UK LLC has harmonised the age / date of birth data provided by LPS and made it available to researchers as part of the UK LLC managed demographic dataset. This can be requested as part of a project application or amendment.
N.B. That some LPS provide data on deceased participants to UK LLC, while some do not. UK LLC uses year of birth as a proxy for age, but it should be noted that a number of these participants may be deceased.
Harmonisation process#
LPS participants’ years of birth were calculated in the following ways:
Date of birth: exact year of birth calculated
Age at a given time point: a likely year of birth was calculated based on the date of survey completion
Age range: an approximate date of birth was calculated assuming participants were at the mid-point of the age range at the time of survey completion
No age or date of birth (birth cohort studies): a year of birth generated from the year of cohort recruitment (e.g. BCS70, NCDS58)
No age or date of birth (all other LPS): year of birth recorded as missing