Time Is Brain—Quantified

Quantitative Analysis Illustrates Enormity of the Diminutive Phrase

In three short words, the phrase “time is brain” succinctly captures the rapid progression of brain damage during stroke and reinforces the importance of rapid medical intervention. Its simplicity lends itself naturally to ubiquity (reflecting its genesis from Benjamin Franklin’s still-popular aphorism, “time is money”), and the phrase remains a popular theme in messaging about stroke and other hypoxic-ischemic injuries, including traumatic brain injury and cardiac arrest.

In patients experiencing a typical large vessel acute ischemic stroke, 120 million neurons, 830 billion synapses, and 714 km (447 miles) of myelinated fibers are lost each hour. In each minute, 1.9 million neurons, 14 billion synapses, and 12 km (7.5 miles) of myelinated fibers are destroyed. Compared with the normal rate of neuron loss in brain aging, the ischemic brain ages 3.6 years each hour without treatment.

In addition to its significance as a qualitative call to action, the phrase carries serious quantitative firepower. Utilizing a systematic review of literature, Jeffrey L. Saver, MD (from the Stroke Center and Department of Neurology, University of California, Los Angeles) endeavored to quantify the scope of brain loss during a typical ischemic stroke. His effort, published in the American Stroke Association journal (Stroke. 2006; 37: 263-266), lends quantitative impact to the diminutive phrase. The following is excerpted from the article, a full version of which is available online at the AHA’s online repository: