Freeze number 15 dated February 2026#

Due to the UK LLC pooled sample being dynamic and the denominator changing over time, the UK LLC establishes a ‘data freeze’ of the pooled sample each quarter. Approved users are provisioned data against a set freeze which fixes their denominator at the start of their project and this remains fixed throughout the course of the project.

To cite this freeze: UK Longitudinal Linkage Collaboration (UK LLC). (2026) Freeze number 15 dated February 2026. UK Longitudinal Linkage Collaboration (UKLLC). https://10.71760/ukllc-freeze-00015

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Table 1: Participants enrolled in LPS and included in the UK LLC resource#

Variation in contribution rates between LPS is mostly due to differences in fair processing. UK LLC continues to work with LPS to establish the governance permissions necessary to maximise the number of enrolled participants in the UK LLC resource.

LPS N participants enrolled in LPS N (%) participants sent to UK LLC N participants not sent to UK LLC
AIRWAVE 53244 52914 (99.4%) 330
ALSPAC 32144 6307 (19.6%) 25837
BCS70 18888 9337 (49.4%) 9551
BIB 29664 28590 (96.4%) 1074
ELSA 18807 9080 (48.3%) 9727
EPICN 30445 15755 (51.7%) 14690
EXCEED 11873 11159 (94.0%) 714
FENLAND 12435 12071 (97.1%) 364
GENSCOT 25152 22379 (89.0%) 2773
GLAD 93477 90558 (96.9%) 2919
MCS 40207 35091 (87.3%) 5116
NCDS58 18563 9670 (52.1%) 8893
NEXTSTEP 15629 7451 (47.7%) 8178
NICOLA 8739 5247 (60.0%) 3492
NIHRBIO_COPING 17183 17146 (99.8%) 37
NSHD46 5362 4289 (80.0%) 1073
SABRE 5251 4719 (89.9%) 532
TEDS 27890 11225 (40.2%) 16665
TRACKC19 20630 19633 (95.2%) 997
TWINSUK 17241 16632 (96.5%) 609
UKHLS 166979 166816 (99.9%) 163
UKREACH 24972 21583 (86.4%) 3389
Total 694775 577652 (83.1%) 117123

Footnotes: Figures for N participants enrolled in LPS were originally provided by the respective studies, and we are working to improve the accuracy and completness of these figures.

Table 1 exclusions: The total number of participants not sent to UK LLC with reason for exclusion#

Exclusion reason N participants
(i) Excluded because they died <2020 16546
(ii) Excluded because they died >=2020 1183
(iii) Excluded because they withdrew from LPS 19842
(iv) Excluded because they dissented from UK LLC 2783
(v) Excluded because they dissented from record linkage 32471
(vi) Excluded because governance not established 34064
(vii) Excluded for other reasons 10234

Footnotes with further details about exclusion criteria

(i) & (ii) UK LLC does not prohibit LPS from sending data for participants who have died. However, some LPS have policies which preclude these participants from inclusion in the resource. Data for participants who died on or after January 1, 2020 are particularly important for COVID-19 research, and so LPS were requested to send these data where possible.

(v) Participants who have dissented from linkage can still be included in the UK LLC resource, with permission flags set accordingly. However, some LPS policies preclude participants from inclusion.

Where a participant was excluded for more than one reason, LPS were asked to count participants once using the exclusion hierarchy (i-vii).

Information presented in Table1 was provided by the LPS at the latest quarterly File1 update corresponding with the freeze name printed at the top of this notebook.