Glenn Dropped From Part of Study on Sleep

John Glenn has been dropped from an experiment to test effects of the hormone melatonin on sleep in space, officials said.

The test of melatonin, which is linked to sleep, is among three objectives in a sleep-disorder study that involves Glenn and another crew member in a space shuttle flight to be launched next week. The 77-year-old astronaut will continue with the other elements of the sleep study and will conduct about 10 experiments in orbit, officials said Wednesday.

Dr. Charles A. Czeisler, a Harvard Medical School researcher supervising the experiment, said Glenn twice took melatonin during the ground-based part of the sleep study.

Afterward, the scientist said he observed “a physical finding” that would exclude Glenn from taking melatonin in space. He said the conclusion was based on experiment criteria filed with the Food and Drug Administration.

“I later learned that the physical finding was well known to NASA and had been for some time,” said Czeisler. NASA officials refused to discuss the “physical finding,” contending that as part of Glenn’s medical record it is protected under privacy regulations.

The FDA considers melatonin a food supplement, and the compound can be bought without a prescription. Studies have suggested that the hormone, produced by the pineal gland, can improve sleep if taken at the correct time of day, but most experts believe more study is needed.

Melatonin has been shown to cause confusion and headaches. In animal studies, the hormone also has been shown to constrict blood vessels. This, says the FDA, means that melatonin “could be dangerous for people with high blood pressure or other cardiovascular problems.”

Asked if this applied to Glenn, NASA officials would not answer, citing privacy regulations.

The loss of melatonin data from Glenn is not a serious setback for the experiment since his role in the study was mostly to examine the effects of advanced age on sleep in space, Czeisler said.