Elevated blood pressure (hypertension) is one of the most common chronic medical conditions in adults. It adversely affects multiple organs including the brain, heart, eyes and kidneys, and promotes vascular damage that impacts still other organ systems. Blood pressure control is generally associated with reduced morbidity and mortality, although this is not uniform for all drugs and in all patient groups. The prevalence of hypertension increases with age, consequently it is particularly common in the Medicare population. Besides its high prevalence, hypertension generally requires drug treatment – and control to desired levels often requires more than one drug – so that the population impact of prevalence, compounded by cost, is substantial.
It is generally agreed that thiazide diuretics are the best first-line treatment for uncomplicated hypertension. If blood pressure is inadequately controlled by a thiazide there is very little evidence to assist clinicians in selecting the next step from the options available. The increasing average age of the US population is generating a parallel increase in people with hypertension, so that the need for evidence to inform treatment is pressing. Since a clinical trial to address this question is unlikely, analysis of appropriate existing data is attractive. We will conduct a retrospective analysis using the comprehensive longitudinal electronic health record (EHR), implemented for Geisinger Clinic patients in 1996 and used as the sole-source ambulatory record for all patients since 2001. This resource is robust, with data on a variety of intermediate and firm endpoints, nested within a comprehensive medical record that allows control for potential confounders and effect modifiers, for a large and stable population. Specific aims are:
- to describe patterns of antihypertensive drug use;
- to compare the changes in intermediate measures (e.g., blood pressure, laboratory tests) between treatments added to an initial thiazide diuretic regimen;
- to compare the time elapsed between initiation of a thiazide and initiation of a second line treatment, and discontinuation of that treatment or initiation of further augmentation; and
- to compare the rates of major disease events associated with hypertension between treatments added to an initial thiazide diuretic regimen.
Recommendations that will come from this investigation must be relevant to multiple constituencies including primary care and specialty clinicians, care-managers, consumers, pharmacists and third party payers. A stakeholder group drawn from these constituencies will help set the agenda for these investigations and interact with the investigators as the study proceeds. The stakeholder group will also assist with the design of strategies and materials for dissemination as recommendations emerge.