Approximately 15 percent of strokes are preceded by a transient ischemic attack (TIA), or a “minor stroke.” If identified by a physician, TIAs and minor strokes offer the potential for intervention to prevent a subsequent disabling or fatal stroke. However, the risk for subsequent stroke is unclear. The current estimate for subsequent stroke is 4 percent at one month, and this rate is believed to be an underestimation because of under-recognition of TIAs and incomplete identification of stroke patients. Coull and colleagues used a prospective, community-based study in a county in England to assess the risk of subsequent stroke.

The authors used data from a large study of 90,542 stroke patients cared for by 63 general practitioners between April 2002 and March 2003. The physicians undertook to report patients with suspected TIA or stroke to the study team, which maintained regular contact with the physicians and monitored patient records to ensure that all eligible cases were identified. The study team also monitored emergency department and hospital admission records to identify eligible cases. Minor stroke was defined as a score of up to three on the National Institutes of Health (NIH) stroke scale at initial assessment. Each vascular event was documented, and patients were followed for at least three months to determine outcomes and subsequent events.

Eighty-seven patients with TIA and 87 with minor stroke were identified during the study period. In addition, 83 patients with major stroke (NIH stroke scale score higher than three) were identified and excluded from the study. Fifteen patients with TIA had a subsequent stroke. Two of these patients died, and three became disabled. The remaining 10 patients were diagnosed with minor strokes and entered in the minor stroke analysis.

Sixteen patients with minor stroke had a subsequent stroke. Four of these patients died, and two became disabled. The authors estimate the risk for stroke within seven days of a TIA at 8 percent. The estimated cumulative risk within one and three months is 11.5 and 17.3 percent, respectively. Risks for a subsequent stroke at these three time points are similar after a minor stroke (i.e., 11.5, 15.0, and 18.5 percent, respectively). Eight patients with major stroke did not seek medical attention after the initial event. The authors estimate that the cumulative risk for stroke in patients who seek medical care one week, one month, and three months after TIA is 7.2, 8.4, and 13.3 percent, respectively; after a minor stroke, the cumulative risk for stroke is 7.2, 10.9, and 14.6 percent, respectively.

The authors conclude that in the population studied, the risk for stroke following a TIA or a minor stroke is substantially higher than had been believed. They calculate that 8 to 12 percent of such patients have a major stroke within one week, 11 to 15 percent within one month, and up to 18.5 percent within three months. In addition to increased medical vigilance for early diagnosis and prompt intervention following a TIA or minor stroke, improved public awareness is essential to ensure that all eligible patients are brought to, or seek, medical attention quickly.

editor’s note: These results are alarming as the “baby boomers” enter age groups in which TIA and minor strokes become more common. The finding that almost 20 percent of patients have a major stroke within three months of a TIA or minor stroke certainly warrants greater attention to recognizing and aggressively treating patients who experience such events. The patients in this study were not generally healthy and carried a heavy burden of stroke-related risk factors (average age was 75 years, one third of the TIA patients reported a previous episode, more than one half were taking antiplatelet therapy, and one half were being treated for hypertension). Although physicians and patients must take all TIAs or stroke events seriously, the risk for a serious subsequent stroke could be lower in younger patients with fewer risk factors.—a.d.w.