Use of electronic primary care records to obtain control populations for assessing excess risk of long-term morbidity and mortality in chronic diseases

Date of ISAC Approval: 
06/01/2020
Lay Summary: 
As a result of improvements in treatments and management of chronic diseases, patients are now living longer but with a potentially higher risk of developing comorbidities. A large population of patients now live with both cancer and diseases that affect the heart and blood vessels (known as cardiovascular diseases or CVD). There is some evidence that cancer patients have an elevated chance of developing CVD later in life, and conversely treatments and interventions for CVD may increase cancer risk. However, to understand this interplay further control populations without the disease of interest are required so that researchers can ascertain whether morbidity and mortality are in excess of what would be expected for comparable people without the chronic disease. This project will utilise primary care records to obtain data on control populations without the chronic disease of interest but that share similar characteristics in terms of demographics and other levels of comorbidity. We will exploit the long-term follow-up of these primary care records to estimate the incidence of morbidity and mortality in these people. Our study also has access to population registry data from chronic diseases such as cancer and CVD and therefore the study aims to understand if deaths or long-term morbidity in these data are in excess of what would be expected for comparable people without the chronic disease of interest. Our study will provide resources for other researchers wishing to understand population-level risk and may help to inform health services to target interventions to prevent long-term comorbidity.
Technical Summary: 
There is, now more than ever, an untapped opportunity to utilise disease registry data to address key questions regarding the lifecourse of patients following diagnosis for either cancer or cardiovascular disease stemming from a) continuing increases in scale of registry data, b) longer-term follow-up, and c) possible linkages with other routinely-collected electronic records that record morbidity and mortality. A key aim of our cardio-oncology research programme at the University of Leicester is to use national registry data to determine whether there are excess rates of morbidity and mortality in chronic disease populations and to understand determinants of variations in excess rates. However, to address such questions, control populations are required so that we can ascertain whether rates of morbidity and mortality are in excess of what would be expected for comparable people without the chronic disease of interest. This study will utilise data from primary care records from CPRD. The aim will be to produce lifetables with expected mortality and incidence rates stratified by different types and severity of comorbidities. These lifetables can then be fed into other models (e.g. relative survival / excess rate models). Hence the research will provide a resource for various applied analyses where it is important to ensure expected rates from the reference population represent the rates the exposed (chronic disease) population would have experienced had they been unexposed. Lifetables have previously been published stratified by socio-economic deprivation (https://csg.lshtm.ac.uk/tools-analysis/uk-life-tables/). Our work will extend such ideas to incorporate comorbidity stratification. The study will use Poisson regression and flexible parametric survival modelling as previously described (Bower AJE 2018) to derive these expected rates.
Health Outcomes to be Measured: 
Primary outcome: All-cause and cause-specific mortality identified from ICD 9-10 codes within the CPRD-ONS linked mortality data; Secondary outcome: Incident primary cancers identified from Read codes (CPRD GOLD) and ICD-10 codes (HES APC); Secondary outcome: Non-fatal CVD (coronary artery disease, stroke, heart failure, cardiomyopathy, pericarditis, valvular heart disease and peripheral vascular disease) identified from Read codes (CPRD GOLD) and ICD-10 codes (HES APC).
Collaborators: 

Dr Michael Sweeting - Chief Investigator - University of Leicester
Mr Aiden Smith - Collaborator - University of Leicester
Dr Claire Lawson - Collaborator - University of Leicester
Dr David Adlam - Collaborator - University of Leicester
Mr James Schmidt - Collaborator - University of Leicester
Dr Mark Rutherford - Collaborator - University of Leicester
Dr Michael Sweeting - Corresponding Applicant - University of Leicester
Professor Paul Lambert - Collaborator - University of Leicester
Professor Umesh Kadam - Collaborator - University of Leicester

Linkages: 
HES Admitted;ONS;Patient IMD;Practice IMD (Standard)