Linked electronic health records for research on a nationwide cohort including over 54 million people in England
Authors:   CVD-COVID-UK consortium,   Manuscript drafting and revising, Wood Angela , Denholm Rachel , Hollings Sam , Cooper Jennifer , Ip Samantha , Walker Venexia , Denaxas Spiros , Akbari Ashley , Sterne Jonathan , Sudlow Cathie ,   Data wrangling, QA and analysis (including generating phenotype definitions), Wood (chair) Angela , Denholm Rachel , Hollings Sam , Cooper Jennifer , Ip Samantha , Walker Venexia , Denaxas Spiros , Banerjee Amitava , Whiteley William ,   Figures/graphics, Lai Alvina ,   Consortium coordination (BHF Data Science Centre core team), Priedon Rouven , Sudlow Cathie , Morrice Lynn , Ringham Debbie ,   Public and patient advisory panel, Power Suzannah , Laidlaw Lynn , Molete Michael , Walsh John ,   NHS Digital (coordination, data management/provision, data access request and information governance support Trusted Research Environment support, Coleman Garry , Day Cath , Gaffney Elizabeth , Gentry Tim , Gray Lisa , Hollings Sam , Irvine Richard , Roberts Brian , Spence Estelle , Waterhouse Janet 
Published: February 2021

Objectives

Describe a new England-wide electronic health record (EHR) resource enabling whole population research on Covid-19 and cardiovascular disease whilst ensuring data security and privacy and maintaining public trust.

Design

Cohort comprising linked person-level records from national healthcare settings for the English population accessible within NHS Digital’s new Trusted Research Environment.

Setting

EHRs from primary care, hospital episodes, death registry, Covid-19 laboratory test results and community dispensing data, with further enrichment planned from specialist intensive care, cardiovascular and Covid-19 vaccination data.

Participants

54.4 million people alive on 1st January 2020 and registered with an NHS general practitioner in England.

Main measures of interest

Confirmed and suspected Covid-19 diagnoses, exemplar cardiovascular conditions (incident stroke or transient ischaemic attack (TIA) and incident myocardial infarction (MI)) and all-cause mortality between 1st January and 31st October 2020.

Results

The linked cohort includes over 96% of the English population. By combining person-level data across national healthcare settings, data on age, sex and ethnicity are complete for over 95% of the population. Among 53.2M people with no prior diagnosis of stroke/TIA, 98,721 had an incident stroke/TIA, of which 30% were recorded only in primary care and 4% only in death registry records. Among 53.1M people with no prior history of MI, 62,966 had an incident MI, of which 8% were recorded only in primary care and 12% only in death records. A total of 959,067 people had a confirmed or suspected Covid-19 diagnosis (714,162 in primary care data, 126,349 in hospital admission records, 776,503 in Covid-19 laboratory test data and 48,433 participants in death registry records). While 58% of these were recorded in both primary care and Covid-19 laboratory test data, 15% and 18% respectively were recorded in only one.

Conclusions

This population-wide resource demonstrates the importance of linking person-level data across health settings to maximize completeness of key characteristics and to ascertain cardiovascular events and Covid-19 diagnoses. Although established initially to support research on Covid-19 and cardiovascular disease to benefit clinical care and public health and to inform health care policy, it can broaden further to enable a very wide range of research.