The purpose of this study was to investigate in large scale routine primary care data whether frailty is a prognostic factor for relevant outcomes in the management of hypertension in older people and whether frailty causes effect modification of the association of blood pressure or blood pressure lowering treatment and outcomes in older people.

A retrospective cohort study used linked electronic health records from the Welsh Secure Anonymised Information Linkage (SAIL) databank. All patients had hypertension in the absence of established cardiovascular disease, and were over the age of 65 years in 2007. Systolic blood pressure and frailty, measured using the electronic frailty index were recorded. Patients were followed up for ten years. Time to event analysis measured first ever major adverse cardiovascular or cerebrovascular event (MACCE), all-cause mortality and injurious falls. Adjustment was made for established cardiovascular risk factors.

Inclusion Criteria:

• Patient registered with a general practitioner contributing to SAIL database for at least 1 year
• Patient with blood pressure measured and recorded at any time after 1st January 2007 and before 1st January 2008, was used as the individual's index start date.
• Patient aged 65 years or older at the time of study entry.

Exclusion Criteria:

• Patient did not have a diagnosis of hypertension or did not have blood pressure meeting criteria for hypertension;
• Patient had an established history of cardiovascular disease (previous stroke, heart failure or myocardial infarction) prior to the start date.

Patients living in the community registered with a general practitioner in Wales.