The effect of treating people with reversible ischaemic attacks of the brain and eye on the incidence of stroke in Australia

BACKGROUND: Reversible ischaemic attacks of the brain or eye (RIA) are a risk factor for stroke. Strategies of stroke prevention include vascular risk factor control, antithrombotic therapy, and carotid surgery.

AIMS: To determine the effectiveness, risks and costs of each stroke prevention strategy for patients with RIA and the Australian community, and the effect of treating people with RIA on the incidence of stroke in Australia.

METHODS: Review of data from prospective community-based studies to determine the prevalence of RIA, the incidence of stroke, and the proportion of stroke patients who report a RIA before their stroke; and data from randomised trials to determine the effectiveness, risks and costs of treatments for RIA.

RESULTS: About 111,000 Australians have had a prior RIA. Each year, about 37,000 Australians suffer a stroke, of whom up to 8000 (22%) have had a prior ('warning') RIA. Targeting effective stroke prevention strategies to RIA patients with relevant treatable conditions may reduce the individual's stroke risk by two-thirds (individual strategies) and possibly further (combination strategies). However, because the attributable risk of RIA for stroke is only about 22% (and may be less, given the role of other causal risk factors for stroke), strategies of stroke prevention in RIA patients can only reduce stroke incidence by up to 15% (from 22% to 7%).

CONCLUSIONS: The potential benefits of the 'high risk' approach to stroke prevention appear to be less than the 'population' approach, but both approaches are necessary and complementary. Indeed, the cost of implementing the 'high risk' approach may be less than the cost of the strokes prevented ($255 million; i.e. 15% of $1.7 billion).