Freeze number 16 dated May 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 16 dated May 2026. UK Longitudinal Linkage Collaboration (UKLLC). https://doi.org/10.71760/ukllc-freeze-00016
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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 | 19164 (59.6%) | 12980 |
| BCS70 | 18888 | 18817 (99.6%) | 71 |
| BIB | 29664 | 28590 (96.4%) | 1074 |
| CAPS | 2959 | 2959 (100.0%) | 0 |
| CSSBIO | 12071 | 11269 (93.4%) | 802 |
| ELSA | 19554 | 19554 (100.0%) | 0 |
| 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 | 92551 | 91836 (99.2%) | 715 |
| INTERVAL | 50000 | 34241 (68.5%) | 15759 |
| MCS | 40207 | 35091 (87.3%) | 5116 |
| NCDS58 | 18563 | 18536 (99.9%) | 27 |
| NEXTSTEP | 15629 | 15574 (99.6%) | 55 |
| NICOLA | 8739 | 5247 (60.0%) | 3492 |
| NIHRBIO_COPING | 17183 | 17143 (99.8%) | 40 |
| NSHD46 | 5362 | 4396 (82.0%) | 966 |
| SABRE | 5251 | 4719 (89.9%) | 532 |
| TEDS | 27890 | 17720 (63.5%) | 10170 |
| TRACKC19 | 20630 | 19633 (95.2%) | 997 |
| TWINSUK | 17301 | 16699 (96.5%) | 602 |
| UKHLS | 166979 | 166816 (99.9%) | 163 |
| UKREACH | 24972 | 21581 (86.4%) | 3391 |
| TOTAL | 759686 | 683863 (90.0%) | 75823 |
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 | 13466 |
| (ii) Excluded because they died >=2020 | 669 |
| (iii) Excluded because they withdrew from LPS | 15763 |
| (iv) Excluded because they dissented from UK LLC | 3308 |
| (v) Excluded because they dissented from record linkage | 10036 |
| (vi) Excluded because governance not established | 4921 |
| (vii) Excluded for other reasons | 27660 |
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.
Table 2: Participants in the UK LLC with permission to link to NHS England and their legal basis#
Permission flags are set at a participant level or at an LPS level giving participants or LPS control over which linkages are established or removed. NHS England operates the National Opt Out (NOO) scheme, where individuals can request that their health record is not shared for research purposes. Where explicit and informed consent is in place, the NOO is overwritten. Where opt-out consent approaches are used in conjunction with Section 251 (s251) of the NHS Act 2006, then NOO is fully respected and no records will be accessed. The current NOO rate is 5.4% of the population; information on NOO rates can be found on the NHS England website1. For this reason, the UK LLC anticipates lower linkage rates where s251 is used.
1digital.nhs.uk/services/national-data-opt-out
| LPS | N participants sent to UK LLC | N with permission to link to NHS E | N linked s251 | N linked consent | N linked total |
|---|---|---|---|---|---|
| AIRWAVE | 52914 | 52912 (100.0%) | 44569 (84.2%) | 44569 (84.2%) | |
| ALSPAC | 19164 | 19154 (99.9%) | 911 (10.6%) | 5141 (48.7%) | 6052 (31.6%) |
| BCS70 | 18817 | 8419 (44.7%) | 7456 (88.6%) | 7456 (88.6%) | |
| BIB | 28590 | 28590 (100.0%) | 28503 (99.7%) | 28503 (99.7%) | |
| CAPS | 2959 | 2959 (100.0%) | |||
| CSSBIO | 11269 | 10846 (96.2%) | |||
| ELSA | 19554 | 11437 (58.5%) | 7340 (64.2%) | 7340 (64.2%) | |
| EPICN | 15755 | 15755 (100.0%) | 15178 (96.3%) | 15178 (96.3%) | |
| EXCEED | 11159 | 11142 (99.8%) | 10185 (91.4%) | 10185 (91.4%) | |
| FENLAND | 12071 | ||||
| GLAD | 91836 | 85067 (92.6%) | 71973 (84.6%) | 71973 (84.6%) | |
| INTERVAL | 34241 | 34241 (100.0%) | |||
| MCS | 35091 | 30109 (85.8%) | 22497 (74.7%) | 22497 (74.7%) | |
| NCDS58 | 18536 | 8901 (48.0%) | 7900 (88.8%) | 7900 (88.8%) | |
| NEXTSTEP | 15574 | 6401 (41.1%) | 5851 (91.4%) | 5851 (91.4%) | |
| NIHRBIO_COPING | 17143 | 17143 (100.0%) | 16845 (98.3%) | 16845 (98.3%) | |
| NSHD46 | 4396 | 4379 (99.6%) | 1401 (96.4%) | 2856 (97.6%) | 4257 (97.2%) |
| TEDS | 17720 | 17720 (100.0%) | 8256 (49.0%) | 701 (80.5%) | 8957 (50.5%) |
| TRACKC19 | 19633 | 19633 (100.0%) | 14499 (73.9%) | 14499 (73.9%) | |
| TWINSUK | 16699 | 16523 (98.9%) | 14039 (85.0%) | 14039 (85.0%) | |
| UKHLS | 166816 | 39945 (23.9%) | 6818 (17.1%) | 6818 (17.1%) | |
| UKREACH | 21581 | 21581 (100.0%) | 18510 (85.8%) | 18510 (85.8%) | |
| TOTAL | 683863 | 485236 (71.0%) | 39785 (64.0%) | 271644 (64.2%) | 311429 (64.2%) |
Footnotes
Participants in SABRE do not currently permit linkage to NHS England and therefore do not feature in Table 2.
Participants in GENSCOT and NICOLA do not currently have permission to link to NHS England due to governance issues and geographical limitations and therefore also do not feature in Table 2.
CAPS, CSSBIO and INTERVAL have recently joined UK LLC and NHS England linkage updates are now annual. Therefore their linkage will appear missing and will be infilled at a later freeze.
Table 3: Participants in the UK LLC with permission to link to place-based datasets#
Permission flags are set at a participant level or at an LPS level giving participants or LPS control over which linkages are established or removed. UK LLC has four different place-based permission flags that fall into the two categories reported in the table below: (i) Neighbourhood geographies - geographies used to produce official statistics, e.g. census geographies such as Lower Super Output Area (LSOA); and (ii) Address geographies - household level using Unique Property Reference Number (UPRN) or postcode level.
| LPS | N participants sent to UK LLC | N with permission to link to neighbourhood | N linked to neighbourhood | N with permission to link to address or postcode | N linked to address or postcode |
|---|---|---|---|---|---|
| AIRWAVE | 52914 | 52914 (100.0%) | 52914 (100.0%) | ||
| ALSPAC | 19164 | 19040 (99.4%) | 6093 (32.0%) | 19040 (99.4%) | 2546 (13.4%) |
| BCS70 | 18817 | ||||
| BIB | 28590 | 28590 (100.0%) | 28441 (99.5%) | 28590 (100.0%) | 28515 (99.7%) |
| CAPS | 2959 | 2959 (100.0%) | |||
| CSSBIO | 11269 | 11173 (99.1%) | 11173 (99.1%) | ||
| ELSA | 19554 | ||||
| EPICN | 15755 | ||||
| EXCEED | 11159 | 11142 (99.8%) | 9498 (85.2%) | 11142 (99.8%) | 5747 (51.6%) |
| FENLAND | 12071 | ||||
| GENSCOT | 22379 | ||||
| GLAD | 91836 | 91772 (99.9%) | 69015 (75.2%) | 91772 (99.9%) | |
| INTERVAL | 34241 | ||||
| MCS | 35091 | ||||
| NCDS58 | 18536 | ||||
| NEXTSTEP | 15574 | ||||
| NICOLA | 5247 | ||||
| NIHRBIO_COPING | 17143 | 17143 (100.0%) | 16771 (97.8%) | 17143 (100.0%) | 7935 (46.3%) |
| NSHD46 | 4396 | 2929 (66.6%) | 2827 (96.5%) | 2929 (66.6%) | 2054 (70.1%) |
| SABRE | 4719 | 1009 (21.4%) | 1009 (21.4%) | 998 (98.9%) | |
| TEDS | 17720 | 849 (4.8%) | 578 (68.1%) | 849 (4.8%) | |
| TRACKC19 | 19633 | ||||
| TWINSUK | 16699 | 16396 (98.2%) | 13861 (84.5%) | 16396 (98.2%) | 8185 (49.9%) |
| UKHLS | 166816 | ||||
| UKREACH | 21581 | 21581 (100.0%) | |||
| TOTAL | 683863 | 277497 (40.6%) | 147084 (53.0%) | 252957 (37.0%) | 55980 (22.1%) |
Footnotes
Linkage to neighbourhood is reliant and calculated from linkage to NHS England where LSOA is available. Therefore studies and participants who do not have permission or have not yet been linked to NHS England data will have no linkage to neighbourhood geographies.
Postcode and address level linkage updates are annual, so there may be a lag between participants being provided to the UK LLC and linkage being established. Where a study has recently set permissions to enable linkage or have just joined UK LLC the linkage rate will appear missing and will be filled at a later freeze date.