Medicine: It's the Blood Flow

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How old a man is may have little to do with his age in years. Some men age much faster than others, so that doctors have said: "A man is as old as his arteries." The difficulty has been to find a way of measuring physiological age. Now, the University of California's Dr. Hardin Jones and his colleagues think they have the answer in the amount of blood flowing through the tissues. The more blood the younger the tissues, and hence the younger the body.

At first Dr. Jones had to measure the blood flow by holding a Geiger counter over the muscle of a subject who had inhaled a radioisotope of an inert gas such as krypton or argon. That was expensive and took a long time. Now, by measuring the carbon dioxide generated in muscles during exercise, Dr. Jones can get his answers in a few minutes.

From tests on more than 500 industrial workers, he has found that the average 18-year-old has 25 cc of blood passing through one liter of muscle per minute. At 25, the average shows a sharp drop, to 15 cc. And by age 35, it is down to 10 cc. But there are enormous variations between seemingly healthy people, e.g., a well-preserved specimen of 60 may have the same blood flow as a debilitated stripling of 20. And so, Dr. Jones reasons, he might be a better employment risk than many of his juniors. One possible use of the California researchers' findings: fixing retirement policies on well-being rather than on age alone.