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The overuse of antibiotics in early childhood could be partly responsible for the alarming rise in asthma and allergies in recent years, a new study suggests.

The lead researcher, Martin Blaser of the New York University School of Medicine, believes in the so-called hygiene hypothesis, which states that young children need to be exposed to lots of microbes for the healthy and normal development of their immune systems.

However, the regular use of antibiotics, plus improved sanitation, has significantly reduced some routine childhood infections - including a once-common stomach bacterium called helicobacter pylori.

Dr. Blaser and fellow researcher Yu Chen found that people who carry a particularly virulent strain of H. pylori were 40 per cent less likely to have asthma at an early age than those who didn't carry the strain.

"Helicobacter is an ancient organism that everyone used to have in the stomach - and now it's disappearing," Dr. Blaser said.

"Less than 10 per cent of kids in Canada and the U.S. currently carry it ... At the same time, asthma rates have been rising."

This suggests, he said, that exposure to microbial infections in early childhood prevents or diminishes the development of asthma and allergies.

There is, however, an ironic twist to the latest research. Earlier studies have shown that H. pylori can also trigger stomach cancer and peptic ulcers in adults.

H. pylori is a "complex" organism "that has its cost and benefits to us," said Dr. Blaser, whose study was published in the journal Archives of Internal Medicine.

Failing sight alters art

What you see on the canvas of a painting may not always be what the artist had intended.

Two leading lights of the Impressionist movement, Claude Monet and Edgar Degas, both suffered from failing eyesight in their later years and struggled to keep painting.

Monet had cataracts that interfered with his ability to see colours. His later paintings appear dark and muddied.

Degas is believed to have been stricken with a form of macular degeneration.

His work became increasingly coarse, lacking the fine details of his earlier paintings.

Now, a renowned ophthalmologist and art lover has created computer images illustrating how the artists' infirmities would have affected their eyesight.

"The images show, as best I can reconstruct, what these artists would have seen," Michael Marmor of Stanford University in California said in an e-mail interview.

The images, which reveal a muted and blurry view of the world, may go a long way toward explaining the changing artistic styles of the two painters.

"These simulations may lead one to question whether the artists intended these late works to look exactly as they do," said Dr. Marmor, who published his images in the journal Archives of Ophthalmology. "The fact is that these artists weren't painting in this manner totally for artistic reasons."

Monet, fearful of surgery, eventually underwent a cataract-removal operation in 1923. He returned to his original painting style, even throwing away some of the canvases he had painted in the decade he was plagued by cataracts.

The sunshine vitamin

Older people who aren't getting enough vitamin D are at risk of becoming increasingly frail and losing muscle strength, a study in the Journal of Gerontologysays.

Researchers measured the physical performance of 967 people aged 65 or older.

Those with low levels of vitamin D did poorly on a series of tests measuring their walking speed, agility and muscle strength, according to the study led by Denise Houston of Wake Forest University in North Carolina.

Vitamin D is produced in the skin on exposure to sunlight. It is also found in some foods.

The elderly, however, become less efficient at making their own vitamin D and may need supplements.

In fact, there is increasing evidence that even young people don't get enough of the "sunshine" vitamin.

A growing body of medical research suggests it plays a key role in fighting diseases ranging from cancer to the common cold.

ptaylor@globeandmail.com