Major diseases show decline: Doctors remain puzzled

While colon cancer, heart disease and strokes still remain leading killers, they are occurring later on in life

Something strange is going on in medicine. Major diseases, like colon cancer, dementia and heart disease, are waning in wealthy countries, and improved diagnosis and treatment cannot fully explain it.

Scientists marvel at this good news, a medical mystery of the best sort and one that is often overlooked as advocacy groups emphasise the toll of diseases and the need for more funds. Still, many are puzzled.

"It is really easy to come up with interesting, compelling explanations," said David S Jones, a Harvard historian of medicine. "The challenge is to figure out which of those interesting and compelling hypotheses might be correct."

Of course, these diseases are far from gone. They still cause enormous suffering and kill millions each year.

But it looks as if people in the US and some other wealthy countries are, unexpectedly, starting to beat back the diseases of aging. The leading killers are still the leading killers - cancer, heart disease, stroke - but they are occurring later in life, and people in general are living longer in good health.

Colon cancer is the latest conundrum. While the overall cancer death rate has been declining since the early 1990s, the plunge in colon cancer deaths is especially perplexing: The rate has fallen by nearly 50 per cent since its peak in the 1980s, noted H Gilbert Welch and Douglas J Robertson of the Geisel School of Medicine at Dartmouth and the Veterans Affairs Medical Center in White River Junction, Vt., in a recent paper.

Screening, they say, is only part of the story. "The magnitude of the changes alone suggests that other factors must be involved," they wrote. None of the studies showing the effect of increased screening for colon cancer have indicated a 50 per cent reduction in mortality, they wrote, "nor have trials for screening for any type of cancer."

Then there are hip fractures, whose rates have been falling 15-20 per cent a decade over the past 30 years. Though the change occurred when there were drugs to slow bone loss in people with osteoporosis, too few patients took them to account for the effect - for instance, fewer than 10 per cent of women over 65 take the drugs. Perhaps it is because people have gotten fatter? Heavier people have stronger bones.

Heavier bodies, though, can account for at most half of the effect, said Steven R. Cummings of the California Pacific Medical Center Research Institute and the University of California at San Francisco.

When asked what else was at play, he laughed and said, "I don't know." Dementia rates, too, have been plunging. It took a few reports and more than a decade before many people believed it, but data from the US and Europe are becoming hard to wave off.

©2016 The New York Times News Service