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They happen all the time: little glitches in consciousness or control of our bodies. Especially with age. Sometimes they’re actually seizures of some mild variety, or migraines. Other times they are critical interruptions in the flow of blood to the brain.

When these episodes happen, some people feel weak or numb in a particular part or region of their body. Others have difficulty finding words, or blurry vision. The potential symptoms are so diverse that many of us, doctors included, are bad at recognizing or acting on them.

When the blood is away long enough that brain cells die in appreciable numbers, this is a stroke. More often, though, the blood returns quickly, and the person recovers fully. This is the less-discussed phenomenon known as a transient ischemic attack (TIA). But it is no less important.

Often a transient ischemic attack is a warning sign, a prelude to a stroke. Next time, the blood might not return. In that way, even though symptoms resolve by definition, a TIA is actionable. It often means that a person has narrow arteries in their head or neck (atherosclerosis), or an arrhythmia of the heart that results in clots being propelled up into the brain. Both conditions are treatable before a major blockage of the neural vessels occurs. And one of the most critical interventions may be in the hands of the public, in the minutes and hours immediately after an attack.

Today in The Lancet, researchers from the U.K., Sweden, Germany, and the Netherlands report a striking effect of taking aspirin in the immediate aftermath of a TIA. Having reviewed data from more than 40,000 people, the team found that doing so appears to reduce the risk of a stroke within the coming weeks by up to 80 percent.

While it was previously known that aspirin could mildly reduce the risk of strokes after a TIA in the long term (by around 12 percent), the dramatic effect of immediate intervention was not evident. But after a reviewing multiple randomized controlled trials and pooling individual patient data from all available trials of aspirin after a TIA, the researchers write in conclusion, “It is essential that aspirin is given to patients with suspected TIA or minor stroke immediately.”

Graeme Hankey, a professor of medicine and pharmacology at the University of Western Australia who did not take part in the study, concludes in an accompanying editorial that when a person either appears to be having or has had a TIA, aspirin “should be administered immediately. The benefits in reducing the risk and severity of early recurrent stroke are greater than previously recognized.”

“For individuals with stroke-like symptoms that are transient and resolve within minutes to an hour or so,” Hankey writes, “self-administration of aspirin, while awaiting medical assessment, is likely to be safe and of benefit in preventing a recurrent ischemic event of the brain.”

The doses used in different cases varied, so an optimal dose remains to be determined. While aspirin was invented in 1897 as a pain medication, it has been a leading product for Bayer on the basis of its use in blocking a basic enzyme in our blood. The “low-dose” 81 milligrams is sufficient in most people to block an enzyme in our blood that helps platelets stick together. When a person is disposed to arterial blockages—from clotting of the blood, narrowing of the vessels, or, most likely, some combination of both—aspirin can serve as a last-ditch effort to disrupt the blood’s natural clotting process.

This does, of course, mean that taking aspirin can introduce risks for people who are bleeding (or otherwise disposed to untoward bleeding). Around 90 percent of strokes are caused by a loss of blood flow, but the others are caused by too much blood flow, a hemorrhage in the brain.

For people with “stroke-like symptoms” that could possibly be due to hemorrhage, Hankey writes, the overall benefits of self-administration of aspirin are  “likely to offset the risks. But further evaluation of such a public policy is recommended.”

While emergency aspirin is no curative measure in any case, it would appear today to be an accessible, low-cost approach to minimizing the chances of a clot forming that could finish a person with a major stroke. As rates of stroke have been increasing of late, especially among people in their 30s and 40s, the finding is timely. If nothing else, the news should serve to raise awareness of the nature of TIA, and the high risk of strokes and the need for immediate medical attention—even if symptoms have completely subsided.

And lest readers assume that the study was funded by Big Aspirin (it wasn't), the researchers also found that aspirin isn’t especially effective at preventing strokes in the long term. Some of the researchers have previously received money from Bayer—a trapping of the process by which pharmaceutical testing happens—but in this case, they're not pushing for lifelong treatment with a costly medication. The suggestion is that people might keep a $2 bottle on hand in case of emergencies, however subtle.

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