Letters to the Editor

Pacing Alzheimer’s
Science Stats “Alzheimer’s Advancing” (SN: 3/9/13, p. 4) reports a new analysis extrapolating from 2010 U.S. Census data that concludes Alzheimer’s disease will triple by 2050. Omitted in such an analysis is the accelerating advance of science and medicine over the next 40 years. The gloomy prediction makes little sense unless science stops short while the disease continues to progress.
Michael Edelstein, San Francisco, Calif.

Researchers are working hard on treatments for Alzheimer’s. But until they find ways to prevent the disease, more people will continue to be diagnosed. That trend is driven by the demographics of an aging population. —Erika Engelhaupt

Technicalities in 3-D
Rachel Ehrenberg’s article about 3-D printing “The 3-D Printing Revolution” (SN: 3/9/13, p. 20) was informative but did not mention exactly how a 3-D printer would make the complex structures mentioned in the article, such as a human kidney. And how would such a printer make a mechanical object with many moving parts made of different materials that may or may not be directly connected to one another?
Robert Walty, Stephens City, Va.

Researchers are still a long way from printing a functioning kidney, but labs are exploring “bioprinting,” in which the printer lays down cells that can, for example, filter blood like a kidney. Challenges include the need for modeling software that captures the complexity of biological parts. It’s already possible to print objects with moving parts such as gears, though the process is difficult to imagine. You can find videos showing how it works by searching “3D printed wrench” on YouTube. —Rachel Ehrenberg

The 3-D printer has unpredictably powerful potential. But the device is an advance in technology, not science. What contribution by this machine to our knowledge of the universe warrants its coverage by Science News?
William Vietinghoff, Thousand Oaks, Calif.

We chose to introduce our readers to 3-D printing in part because it is an increasingly important tool in basic and applied scientific research. For example, the April 6 issue has an article describing the creation of fluid vortices using a pretzel-shaped plastic wing made with a 3-D printer (SN: 4/6/13, p. 8). On Page 12 of this issue is a 3-D printed polymer skull implant. We considered confining ourselves to scientific applications of 3-D printing, but ultimately decided that the technology’s role in design and the “maker” movement added valuable and interesting context. —Matt Crenson