Predictors of Blood Pressure Control and Associations With Cardiovascular Diseases in Individuals With High Blood Pressure: a CALIBER Study

Current guidelines for the clinical management of hypertension in adults recommend to achieve and maintain blood pressure levels of \<140/90 mmHg. However, it is uncertain what proportion of individuals identified with high blood pressure in primary care actually reach blood pressure control, what factors are associated with attainment of control and to what extent blood pressure control attainment is associated with cardiovascular diseases in a contemporary population of individuals diagnosed with high blood pressure.

The aim of this study is to investigate the extent to which patients achieve blood pressure control and associated risk factors, time to attainment of blood pressure control and whether this time is associated with an increased risk of CVD onset, all-cause and cardiovascular disease and end-stage renal disease.

An increment of 20 mmHg of systolic blood pressure (or approximately equivalent 10 mmHg diastolic blood pressure) is associated with more than a two-fold increase in risk of fatal stroke, and with a two-fold increase in fatal ischemic heart diseases in individuals aged 40-69 years. The management and control of high blood pressure is therefore one of the most important components of primary and secondary strategies for prevention of cardiovascular mortality and morbidity. Current guidelines for the clinical management of hypertension in adults recommend to achieve and maintain blood pressure levels of \<140/90 mmHg. However, it is uncertain what proportion of individuals identified with high blood pressure in primary care actually reach blood pressure control, what factors are associated with attainment of control and to what extent blood pressure control attainment is associated with cardiovascular diseases in a contemporary population of individuals diagnosed with high blood pressure. This is important for clinicians and policy decision makers in order to design and implement effective strategies for patient management.

The aim of this study is to investigate the extent to which patients achieve blood pressure control and associated risk factors, time to attainment of blood pressure control and whether this time is associated with an increased risk of CVD onset, all-cause and cardiovascular disease and end-stage renal disease.

The study will use data from the CALIBER data set of clinically collected electronic health record data from England.

This study is part of the CALIBER (Cardiovascular disease research using linked bespoke studies and electronic records) programme funded over 5 years from the National Institute for Health Research (NIHR) and Wellcome Trust. The central theme of the CALIBER research is linkage of the Myocardial Ischaemia National Audit Project (MINAP) with primary care (Clinical Practice Research Datalink - CPRD) and other resources. The overarching aim of CALIBER is to better understand the aetiology and prognosis of specific coronary phenotypes across a range of causal domains, particularly where electronic records provide a contribution beyond traditional studies. CALIBER has received both Ethics approval (ref 09/H0810/16) and ECC approval (ref ECC 2-06(b)/2009 CALIBER data set).

Eligibility Criteria:
Inclusion Criteria:

* Patients aged 18 and over
* Registered with a participating general practice during the study period
* Minimum one year of records prior to study entry meeting CPRD data quality
* Diagnosed with high blood pressure in the period January 1997 - March 2010

Exclusion Criteria:

* Patients without record of gender
* Patients with prior atherosclerotic disease, as recorded in primary care or hospitalisation data
* Patients with less than 6 months of follow-up since diagnosis of high blood pressure