A recent study by physicians at the Mayo clinic revealed that the prevalence of celiac disease has increased over the last 50 years. Some of the articles reporting on this finding have been somewhat confusing and has glossed over important details of the study. Today I read the original research article, and I have summarized the results of the study below.
What did they do?
The researchers examined blood samples from three groups:
1) Healthy young men whose samples were collected between 1948 and 1952 at Warren Air Force Base (WAFB);
2) Older adults whose samples were collected between 1995 and 2003 in Minnesota (this sample was used in order to provide a control group that was born around the same time as the subjects in the WAFB group);
3) Healthy young men whose samples were collected between 2006 and 228 in Minnesota
The researchers tested blood samples for tissue transglutaminase antibodies (tTGA). They classified the results of the tTGA test as follows: less than 4 U/mL was negative, between 4 and 10 U/mL was weakly positive, and greater than 10 U/mL was positive.
Then, all samples with tTGA results that were categorized as weakly positive or positive were tested for endomysial antibodies (EMA) by indirect immunoflorescence. When either the tTGA or the EMA produced a negative result, then the individual was categorized as not having celiac disease.
The use of EMA to confirm positive tTGA results has been shown in a previous study to correctly identify 97% of people with celiac disease and to correctly classify 100% of those without celiac disease. This means that this test does not overestimate the number of people with celiac disease. So, even though the researchers couldn’t go back in time and do upper endoscopies to make the diagnoses, the blood tests they used were very accurate for correctly classifying people with and without celiac disease.
The researchers also obtained medical record data for the WAFB group for the 45 years after their blood test was taken. The variables of interest included whether they were ever diagnosed with celiac disease and how long they lived.
What did they find?
The prevalence of celiac disease was 0.2% in the WAFB group; 0.8% in the older adult group; and 0.9% in the younger adult group. Thus, the prevalence of celiac disease was 4 times higher in the older adult group than the WAFB group. This is meaningful because both groups were born in the same year, but the group tested recently, in older age had a much higher rate of celiac disease than the group who were tested when they were younger. Why could this be? The researchers speculate that something in the environment has changed since 1950, which increased the risk of developing celiac disease.
The prevalence of celiac disease was 4.5 times higher in the younger adult group than the WAFB group. This is suggests that among people of the same age, the likelihood of having celiac disease is much higher today than it was 50 years ago. This result is not confounded by improved diagnostic techniques or increased awareness of the illness.
During the 45-year follow-up period in the WAFB group, the mortality rate was about 4 times higher for individuals with undiagnosed celiac disease than for those without. Of those with undiagnosed celiac disease who died of known causes, the majority died of cancer.
What can we conclude?
Celiac disease is more common now that it was 50 years ago. The cause of this change is likely environmental and could be related to changes in the “quantity, quality, or processing of cereal.” Alternatively, changes in the type and prevalence of early childhood infections and exposure to bacteria and other pathogens could also affect the prevalence of celiac disease. However, these are only speculations, and further research must be conducted before researchers will be able to provide more definitive explanations.
What does this mean for those of us on the gluten-free diet?
Essentially, nothing because this study was conducted among individuals who had never been diagnosed with celiac disease. We are the lucky ones who have been diagnosed. It is unknown whether being on the diet will change our long-term mortality rate, but evidence from other studies suggests that maintaining a gluten-free diet substantially improves health outcomes for people with celiac disease.
The only way this study may affect us is that it has been getting a lot of press, and the authors stated in a recent press release that the general population should be screened for celiac disease in the same way we are currently tested for high blood pressure and cholesterol. This means that many more people will be joining our ranks, and the gluten-free food and cosmetic products available to us will only get better as the population of those with celiac disease grows.
Dr. Murray’s description of the study:
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