Trends in stroke rates, risk, and outcomes in the United States, 1988 to 2008

Background: Stroke is a major cause of morbidity and mortality. We describe trends in the incidence, outcomes, and risk factors for stroke in the US Medicare population from 1988 to 2008.

Methods: We analyzed data from a 20% sample of hospitalized Medicare beneficiaries with a principal discharge diagnosis of ischemic (n = 918,124) or hemorrhagic stroke (n = 133,218). Stroke risk factors were determined from the National Health and Nutrition Examination Survey (years 1988-1994, 2001-2008) and medication uptake from the Medicare Current Beneficiary Survey (years 1992-2008). Primary outcomes were stroke incidence and 30-day mortality after stroke hospitalization.

Results: Ischemic stroke incidence decreased from 927 per 100,000 in 1988 to 545 per 100,000 in 2008, and hemorrhagic stroke decreased from 112 per 100,000 to 94 per 100,000. Risk-adjusted 30-day mortality decreased from 15.9% in 1988 to 12.7% in 2008 for ischemic stroke and from 44.7% to 39.3% for hemorrhagic stroke. Although observed stroke rates decreased, the Framingham stroke model actually predicted increased stroke risk (mean stroke score 8.3% in 1988-1994, 8.8% in 2005-2008). Statin use in the general population increased (4.0% in 1992, 41.4% in 2008), as did antihypertensive use (53.0% in 1992, 73.5% in 2008).

Conclusions: Incident strokes in the Medicare population aged ≥65 years decreased by approximately 40% over the last 2 decades, a decline greater than expected on the basis of the population's stroke risk factors. Case fatality from stroke also declined. Although causality cannot be proven, declining stroke rates paralleled increased use of statins and antihypertensive medications.