15 percent of healthy Amish octogenarians have “haplogroup X,” a genetic pattern within the mitochondria, which are the regions of cells that generate energy and help guard against deterioration. Haplogroup X is generally found in only 2 percent of Europeans, from whom the Amish descended. In the University of Miami study, only 3 percent of the control group—Amish people who had made it to 80 but suffered from significant disease or disability—had the genetic variant.
Researchers who study aging have long suspected that mitochondria play a role in aging. Mitochondria are responsible for processing metabolized food particles into adenosine triphosphate, which fuels vital cellular processes. They’re also involved in cell growth and differentiation. But the ability of mitochondria to function properly seems to decline with age.
Understanding the reason for that decline—and the genes that might control it—has been challenging. Mitochondria have their own DNA, which is passed down from the mother only. This unique chromosome has variations, called haplogroups. Nine such haplogroups have been well characterized in people of European descent, Scott says. But only haplogroup X was found to be prevalent among healthy aged people in the University of Miami study.
“The advantage of working with a homogeneous population is, you’re reducing the variances that can be associated with the environment,” Crawford says. Mennonites and Amish “don’t drink, don’t smoke. Most do some sort of physical activity. They don’t sit around working on a computer all day.”