The stroke recurrence rate is highest in the first year, particularly in the presence of carotid stenosis. 6 One needs to be clear whether the interventions proposed are mass interventions for populations or aimed at high-risk individuals on which this article predominantly concentrates. The evidence based on randomized controlled trials exists predominantly for pharmaceutical interventions as does economic evaluation of the costs of intervention and their cost effectiveness. Most interventions have either not been tested in randomized controlled trials such as smoking, relatively few across many different types of intervention such as exercise and rehabilitation, or have unclear outcomes. An example of an unclear outcome would be a case-controlled study in which raised homocysteine levels that are associated with increased stroke or cardiovascular disease can be reduced by folic acid and pyridoxine but with an unclear understanding of the relationship of raised homocysteine levels to stroke 1,5 or the outcomes of intervention.
Outcomes are also unclear following the use of oral contraceptives and hormone replacement therapy.
They may all have an impact on long-term outcome and therefore impact on secondary and tertiary prevention. These are, however, not specifically considered in this discussion. There is a progressive increase in risk even at normal levels of blood pressure and clear evidence from randomized trials that reduction of raised blood pressure prevents stroke. It is estimated that only a fifth of hypertensive Americans have optimal therapy. There is a lack of clarity as to the optimal management of hypertension after the onset of stroke illness when autoregulation of cerebral blood flow is lost.