Cases of celiac disease may be on the rise, in large part because people can develop the autoimmune disorder much later in life than previously thought, according to a study published Monday in the Annals of Medicine.
The prevalence of the disease more than doubled among a group of 3,511 seemingly healthy adults between 1974 and 1989, researchers found. By retesting blood samples collected decades ago, they also determined that 15 of the 16 people who had celiac disease were not diagnosed at the time by their doctors.
The findings should prompt physicians and scientists to reexamine some of their fundamental assumptions about the disorder.
"A lot of those rules of thumb have to be reevaluated as we learn more about it and we find patients developing the disease later in life," said Dr. Eric Esrailian, a gastroenterologist at UCLA's David Geffen School of Medicine, who wasn't involved in the study.
Celiac disease is triggered by eating foods that contain gluten, an essential protein found in grains like wheat, barley and rye. Gluten prompts the immune system to destroy the lining of the small intestine, which prevents people from absorbing the nutrients in food and leaves them at risk of malnourishment. Symptoms include diarrhea, weight loss, constipation, anemia and fatigue. An estimated one in 133 people in the U.S. have the disease.
Researchers had thought celiac disease could develop only during childhood, in response to initial exposure to gluten. It didn't seem possible that people could eat gluten with no problems for decades and then suddenly lose their ability to tolerate it.
But that's exactly what researchers from the Center for Celiac Research at the University of Maryland School of Medicine and their colleagues found.
They piggybacked on a study designed to identify risk factors for cancer and heart disease. Participants provided health information and blood samples in 1974 and again in 1989.
The researchers tested those blood samples for biomarkers related to celiac disease. They found that seven had the condition in 1974, none of whom had been diagnosed. By 1989, the number of cases had risen to 16, though only one had been diagnosed.
Overall, the prevalence of the disease more than doubled from 0.21% to 0.45%, the researchers reported. At least two people developed the disorder after they turned 50.
"We were shocked," said Dr. Alessio Fasano, the pediatrician who led the study.
What causes late onset of celiac disease isn't known. People must have a genetic predisposition to it, but scientists aren't sure why gluten intolerance would develop after so many trouble-free years.
Fasano said environmental factors may trigger changes in the immune system that could activate anti-gluten gene. But identifying those factors won't be easy.
"What has changed in the environment in the last 30 years?" Fasano said. "We have more antibiotics, more vaccinations, bioengineered foods, chemicals we haven't been exposed to, and pollutants that haven't been around in the concentrations we have now."