A new study revealed that the prevalence of celiac disease and gluten-related disorders is higher in the northern latitudes of the U.S. compared with the south.
Previous research has shown the prevalence of autoimmune diseases like inflammatory bowel disease, multiple sclerosis and rheumatoid arthritis vary across the “North-South gradient.” This may be linked to differences in sunlight or UVB radiation exposure, which is “generally lower in the northern latitudes and predispose to vitamin D deficiency,” Joseph A. Murray, MD, of the division of gastroenterology and hepatology at the Mayo Clinic in Rochester, Minn., and colleagues wrote. In celiac disease, geographic differences in availability of and adherence to a gluten-free diet may also play a role in this varying prevalence, they added.
To better understand geographic, demographic and clinical factors associated with the prevalence of celiac disease and gluten avoidance in the U.S., Murray and colleagues conducted a population-based study using the U.S. National Health and Nutrition Examination Survey, including data from 2009 through 2014 on 22,277 participants aged 6 years and older.
Joseph A. Murray
Overall, 0.7% had celiac disease and 1.1% adhered to a gluten-free diet but were not diagnosed with celiac disease. A higher proportion of people had celiac disease at latitudes of 35 to 39 degrees north (OR = 3.2; 95% CI, 1.4-7.1) or above 40 degrees north (OR = 5.4; 95% CI, 2.6-11.3) compared with those who lived below 35 degrees north. Prevalence increased from 0.2% to 0.6% to 1.2% across these latitudes, and the association was independent of race, ethnicity, socioeconomic status and BMI.
Celiac disease was also more common among people with a higher education and those with normal weight vs. overweight or obesity, and was less common among non-Hispanic black people.
When analyzing region rather than latitude, the risk for celiac disease was more than twice as high in the Northeast compared with the South (OR = 2.3; 95% CI, 1.1-4.7).
Similarly, adherence to a gluten-free diet without a diagnosis of celiac disease was twice as prevalent above 40 degrees north latitude (1.6%) compared with latitudes below 35 degrees north (0.8%) and between 35 and 40 degrees north (0.7%), and this association was also independent of demographic factors and BMI. Regional analysis showed gluten-avoidance without a diagnosis of celiac disease was higher in the Northeast (OR = 2.9; 95% CI, 1.6-5.1) and in the West (OR = 2.5; 95% CI, 1.3-4.8) compared with the South.
Finally, investigators found that people who were undiagnosed but had positive celiac serology tests had lower levels of B12 and folate, and diagnosed celiac patients had lower levels of hemoglobin compared with healthy individuals without celiac disease. They found no differences between groups in albumin, calcium, iron, ferritin, total cholesterol, vitamin B6 or vitamin D.
Previous studies examining geographic variations in celiac disease prevalence have shown that, similarly, celiac disease was more common in the north vs. the south of India, “and correlated with greater wheat intake, but not with genetic background,” Murray and colleagues wrote. “In contrast to our findings, a recent large Swedish study reported a higher celiac disease incidence among children born in southern Sweden compared with the north. However, these ‘opposite’ latitude gradients may result from [Sweden’s higher northern latitude and racial/ethnic differences compared with the U.S.].”
“Further studies are needed of lifestyle and environmental factors that mediate the association of celiac disease with latitude, as well as integration with genetic data to account for potential interaction with genetic risk factors,” they concluded. – by Adam Leitenberger
Disclosures: The researchers report no relevant financial disclosures.