New research suggests celiac disease can develop at any age -- even in seniors who seemed for decades to be able to eat the foods that trigger the autoimmune disease.

According to research published in the Annals of Medicine, there has been a five-fold increase in the prevalence of celiac disease during the past 30 years, and a lot of these new cases are being diagnosed in elderly people.

The findings could prompt doctors to rethink some of their most basic assumptions about the disorder -- including that the disease begins in childhood.

Celiac disease is triggered by eating gluten, the protein in many grains including wheat, barley, and rye. The condition prompts the immune system to destroy the lining of the small intestine. That then prevents people from absorbing nutrients and causes diarrhea, weight loss, anemia and fatigue.

It has long been assumed that celiac disease developed during childhood, following the first exposure to gluten, and that patients diagnosed in adulthood had likely had the condition all their lives but hadn't realized it.

This new research suggests it's possible that some people can eat gluten with no problems for decades and then suddenly lose their ability to tolerate it.

"You're never too old to develop celiac disease," Dr. Alessio Fasano, director of the University of Maryland's Mucosal Biology Research Center and the Center for Celiac Research, which led the study, said in a news release.

For the study, Fasano and others studied the prevalence of celiac disease by analyzing the blood markers from more than 3,500 U.S. adults who participated in a two-part study conducted in 1974 and in 1989.

They found that the number of people in the study with blood markers of celiac disease increased from one in 501 in 1974 to one in 219 in 1989. The Celiac Disease Foundation states that one out of 133 people now has celiac disease.

As the people in the study aged, the incidence of celiac disease rose. That echoes the findings of a 2008 Finnish study in Digestive and Liver Disease that found the prevalence of celiac disease in the elderly to be nearly two and a half times higher than the general population.

"You're not necessarily born with celiac disease," said Dr. Carlo Catassi, the lead author of the paper and co-director of the Center for Celiac Research. "Our findings show that some people develop celiac disease quite late in life."

In light of the findings, Dr. Catassi suggests that doctors should consider screening their elderly patients for celiac disease if they complain of intestinal problems, even if they have tested negative for the condition in the past.

It remains a mystery how and why some people lose their tolerance to gluten. Some genetic markers have been identified, but even those with the markers aren't always destined to develop the autoimmune disease.

That suggests that some environmental factor or factors other than gluten must be in play, says Dr. Fasano.

"Our study shows that environmental factors cause an individual's immune system to lose tolerance to gluten, given the fact that genetics was not a factor in our study since we followed the same individuals over time," said Fasano.

Identifying those factors could lead to new treatments and perhaps even ways to prevent the disease. Researchers at the University of Maryland Center for Celiac Research are working toward that goal, says Fasano.