'Heart failure' (HF) is when the heart can't pump blood properly around the body. People with HF often have poor quality of life, increased hospital admissions and die earlier. HF is often as a result of high blood pressure and heart attacks and worsens as a result of other conditions such as diabetes and chronic kidney disease. Previous studies have shown that these conditions differ among ethnic groups and yet the nature of the cause and consequences of HF in these populations is unknown. We don't know which of these conditions or other risk factors are most important for the development of HF in different ethnic groups or whether the factors that might make outcomes worse after HF onset differ among ethnic groups. This project will investigate (i) whether factors leading to HF have changed over the past 20-years and whether they differ among ethnic groups and (ii) after HF has developed, whether hospital utilisation and death rates have changed over time or differ among ethnic groups and whether the length of life following HF diagnosis differs by ethnic group. This evidence is important for the tailoring of primary prevention and risk reduction strategies to specific groups to improve outcomes.
Heart failure (HF) is a leading cause of hospitalisation and death globally and is reaching epidemic proportions in the UK with predicted further growth as populations' age. HF has diverse aetiological pathways which might be triggered or moderated by wide ranging individual, clinical and environmental risk factors. Whilst UK evidence is limited, prior American studies have suggested that incidence of HF and its outcomes differ among ethnic groups. Furthermore, these disparities have been explained by differences in the risk factors and aetiological pathways leading to heart failure among groups, which may change as a result of population and social dynamics within specific groups. In two phases this study aims to investigate (i) whether there are differences in aetiological or risk factors among ethnic groups with new onset HF in the UK and whether temporal changes exist over 20-years (ii) using Poisson models, investigate whether rates of hospital utilisation and deaths differ over time among ethnic groups (iii) using Cox regression, compare time to death following HF among ethnic groups and (iv) residual life and years of life lost due to HF onset, by ethnic group, will be estimated by quantifying standardised (adjusted) survival in people with and without HF.
All-cause admissions:
Hospital admissions will be identified through linkage of CPRD to HES data. Single hospital admissions will be defined by unique hospital spell numbers and date of admission will be used as the index admission date. For any admission with a discharge date at the end of the HES data year (31st March), subsequent admissions on the 1st April will be discounted. This is to allow for the artificial creation of two hospital spells by HES where one spell spans the end of HES data year.
Cause-specific admissions:
Three categories of cause-specific admissions will be used including HF, other cardiovascular or non-cardiovascular admissions. Codes will be based on ICD-10 codes as follows: Heart failure (I50), other cardiovascular (chapter IX 'diseases of the circulatory system' excluding I50) and non-cardiovascular (other ICD-10 chapters excluding chapter 1X).
Hospital bed days:
Hospital bed days will be the total number of nights in hospital calculated by the difference between admission and discharge dates.
All-cause death:
The outcome will be all-cause mortality defined as death by any cause recorded in the patients CPRD or linked HES or ONS records. Given that there are a number of different entry types within the CPRD that indicate a death event and each has an associated date, there may be multiple records and dates for any one patient. The study date of death will be derived using a CPRD verified algorithm which takes the earliest of the patient transfer out date (with reason 'death'), first statement of death Read code or date of death/record added in the death administration area of the CPRD. Where death dates occur in all 3 linked records the earliest will be used.
Cause-specific death:
In England and Wales, there is a legal requirement to register all deaths with the Office of National Statistics (ONS) which provides a complete data source for mortality statistics including cause of death coded using International Classification of Diseases (ICD) codes. However, assignment of a specific cause of death is subject to error, particularly when the patient has a number of underlying diseases or health factors. HF itself is considered a mediator between disease and death and is therefore ill-defined as a cause of death in favour of a more specific cause (such as myocardial infarction). HF is often applied where the aetiology is not known but this is not consistent and underreporting of circulatory diseases on death certificates is common. Conceptually, in considering HF as the cause of death, all deaths that are directly or indirectly caused by HF or its treatment should be included.36 An example would be a patient with HF who dies of renal failure secondary to the HF who is then coded with renal failure as the cause of death.
So HF death might result in an aetiological cause being coded (such as myocardial infarction) or by a related cause subsequent to HF such as renal failure or respiratory arrest, with HF listed as an additional cause. Given the lack of sensitivity of heart failure death recording, cause-specific death will be defined in two ways. Firstly, by a ICD-10 code for HF (I50) as the primary 'underlying cause of death' or as any of the 'recorded causes of death' in the ONS record and secondly, by a broader definition including HF as the primary 'underlying cause of death' or as any of the 'recorded causes of death' or an 'other cardiovascular diseases' code used as the primary 'underlying cause of death'. Codes will be based on ICD-10 codes as follows: Heart failure (I50), other cardiovascular (chapter IX 'diseases of the circulatory system' excluding I50) and non-cardiovascular (other ICD-10 chapters excluding chapter 1X).
Date of death will be defined by the first entry in the merged HES-ONS file or CPRD but cause of death will use the merged HES-ONS file.
Claire Lawson - Chief Investigator - University of Leicester
Claire Lawson - Corresponding Applicant - University of Leicester
Francesco Zaccardi - Collaborator - University of Leicester
IAIN SQUIRE - Collaborator - University of Leicester
Kamlesh Khunti - Collaborator - University of Leicester
Laura Gray - Collaborator - University of Leicester
Melanie Davies - Collaborator - University of Leicester
Umesh T Kadam - Collaborator - Keele University
HES Admitted Patient Care;ONS Death Registration Data;Patient Level Index of Multiple Deprivation