Aging might be inevitable, but many of its related illnesses are slowly loosening their grip. A host of diseases are diminishing in wealthy countries, and this boon can't be entirely explained by advances in treatment, screening or diagnostics, writes Gina Kolata for The New York Times.

For example, about half as many people are dying from colon cancer now as during its peak in the 1980s, physicians wrote in a recent paper in the New England Journal of Medicine. Rates of heart disease, dementia, hip fractures are decreasing as well, and people are remaining in good health longer.

It could be that the aging processes within cells are changing, Steven R. Cummings of the California Pacific Medical Center Research Institute and the University of California at San Francisco told Kolata.

For now, though, this is just speculation. There are many possible explanations for this mystery. In the case of Alzheimer's, which shares some risk factors with heart disease, people's increasing abilities to keep blood pressure or cholesterol in check might be one factor.