Letters from the September 1, 2007, issue of Science News

Risk reversal?

“Diabetes drug might hike heart risk” (SN: 6/23/07, p. 397) reports 86 heart attacks among 15,560 rosiglitazone (Avandia) users, versus 72 others in a control group of 12,283. A study coauthor then says that “after statistical adjustment, that yields a 43 percent higher risk of heart attacks among rosiglitazone users.” Simple arithmetic would seem to indicate it was the control group that had a slightly higher risk.

Vincent Fecher
San Antonio, Texas

The study reported was based on data from diverse trials. Simply adding all the numbers to reach a risk calculation would require that the studies be identical in design. Since they were not, scientists had to account for various differences. But it’s fair to say that the results appear counterintuitive.—N. Seppa

Let’s be careful

“Crossing the Line: Technique could treat brain diseases” (SN: 6/23/07, p. 387) describes attaching a drug molecule to a molecule from the rabies virus that enables the drug to cross the blood-brain barrier. This suggests a possible danger if the ability to produce the molecule could be transferred to the genomes of disease organisms in the wild. If the field of genetic engineering for drug production doesn’t already have guidelines to cover such risks, now might be the time to develop them.

Kenneth Timoner
Edina, Minn.

By the book

Your review of Alex Vilenkin’s book Many Worlds in One: The Search for Other Universes (SN: 6/30/07, p. 411) contained an often-made error. In Guth’s inflation model, during the first “zillionth of a second,” the universe did not inflate “to cosmic scale.” It inflated to about the size of a large grapefruit. Then it began its slow expansion.

Martin Gardner
Norman, Okla.

Gems with impact

With respect to the article on kimberlites, diamonds, and mantle fractures (“A Gemstone’s Wild Ride,” SN: 6/30/07, p. 412), may I suggest that the fractures in question emanate from hypervelocity bolide impacts on Earth. There is ample spatial correlation between impact craters formed by oblique impacts with crustal-fracture systems that propagated outward along the direction of impact.

Gregory C. Herman
New Jersey Geological Survey
Trenton, N.J.

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