Celiac disease patients may face increased risks of heart disease and asthma, according to two separate analyses of Swedish national data.
And that might be true to some extent even if they stick to a gluten-free diet, said Dr. Jonas Ludvigsson of Orebro University Hospital, who led both studies.
In one of the two studies, published online January 24th in Circulation, Dr. Ludvigsson and his colleagues found that patients with celiac disease were 22% more likely to die of ischemic heart disease during follow-up than the reference group, while risk for people with intestinal inflammation but no celiac disease was 32% greater.
People with celiac disease antibodies in their blood but no symptoms had no extra risk of dying from heart disease, however.
The research team had information on close to 45,000 individuals who'd had intestinal biopsies, including 28,190 with celiac disease and villous atrophy; 12,598 with inflammation of the small intestine but no villous atrophy; and 3,658 with positive celiac disease serology but no intestinal inflammation or villous atrophy.
The researchers compared each group to a reference group of nearly 220,000 people who hadn't undergone intestinal biopsies.
The entire intestinal biopsy cohort, including people without celiac disease, had a 20% higher risk of heart disease during follow-up, typically a 6- to 8-year period.
The increased risk was relatively "modest," Dr. Ludvigsson and his colleagues note. For example, there were 24 more heart attacks per 100,000 person-years among the celiac disease patients than in the reference population, and 102 more deaths per 100,000 years among people with intestinal inflammation but no celiac disease.
Dr. Ludvigsson told Reuters Health via email that "patients with inflammation but no villous atrophy have not traditionally received a gluten-free diet. Hence, persistent inflammation in this (latter) patient group may explain their high risks of ischemic heart disease."
The researchers don't know whether patients with confirmed celiac disease were avoiding gluten.
"Unfortunately," Dr. Ludvigsson told Reuters Health, "we have no individual-based data on gluten-free diet adherence. We know from earlier studies that 83% of the patients adhered to a gluten-free diet, but if these individuals were at increased risk or if the risk increase was restricted to those 17% with bad adherence we do not know."
"My personal guess," he added, "is that the risk increase is found both in those on a gluten-free diet and in those not on a diet, but that it is higher in those not on a diet. But I have no hard evidence to confirm this."
In a second study, Dr. Ludvigsson and his colleagues found that people with celiac disease were 60% more likely to develop asthma, relative to those without the disease.
For every 100,000 people with celiac disease, 147 will have asthma that would not have occurred in the absence of the autoimmune digestive disorder, according to the researchers.
Individuals with asthma are also more likely to eventually develop celiac disease, they reported in a February 11th online paper in the Journal of Allergy and Clinical Immunology.
For this study they compared the same 28,000 Swedes with celiac disease to more than 140,000 controls.
It's unclear what might explain the association, Dr. Ludvigsson said. "Personally, I think the role of vitamin D deficiency should be stressed."
People with celiac disease are more likely to develop osteoporosis and tuberculosis, both diseases in which vitamin D plays a role. If a person with celiac disease also has low levels of vitamin D, this could in turn affect the immune system, which could increase the risk of developing asthma, he said.
"Another potential mechanism could be that asthma and celiac disease share some immunological feature," he added. "If you have it, you are at increased risk of both diseases."
Circulation . Abstract
J Allergy Clin Immunol. Abstract
Anne Harding and Alison McCook • Reuters Health Information © 2011