# Understanding the harmonisation of LPS year of birth (age) variables >Last modified: 03 Jul 2025
UK LLC has harmonised participants' year of birth is recorded across all LPS
## 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