The association between prevalence of celiac disease and geographic region is incompletely understood, but the occurrence of several autoimmune disorders has been found to vary along a North−South gradient.
Dr Constance Ruhl and colleagues from Maryland, USA examined geographic, demographic, and clinical factors associated with prevalence of celiac disease and gluten-free diet in the United States.
In a population-based study, the researchers analyzed data on gluten-related conditions from the National Health and Nutrition Examination Survey, from 2009 through 2014, on 22,277 participants 6 years and older.
The team identified persons with celiac disease based on results of serum tests for IgA against tissue transglutaminase and endomysium or on both a health care provider diagnosis and adherence to a gluten-free diet.
|Less than 1% of participants to have celiac disease|
Gluten avoidance without celiac disease was defined as adherence to a gluten-free diet without a diagnosis of celiac disease.
The researchers compared mean serum levels of biochemical and nutritional markers based on status of gluten-related conditions.
The team found that less than 1% of participants to have celiac disease, and just over 1% of participants to avoid gluten without celiac disease.
Celiac disease was more common among individuals who lived at latitudes of 35°−39° North or at latitudes of 40° North or more than individuals who lived at latitudes below 35° North, independent of race or ethnicity, socioeconomic status, and body mass index.
Gluten avoidance without celiac disease was more common among individuals who lived at latitudes of 40° North or more, independent of demographic factors and body mass index.
Participants with undiagnosed celiac disease had lower mean levels of vitamin B-12 and folate than persons without celiac disease.
The research team observed that participants with a health care provider diagnosis of celiac disease had a lower mean level of hemoglobin than persons without celiac disease.
Mean levels of albumin, calcium, iron, ferritin, cholesterol, vitamin B-6, and vitamin D did not differ between participants with gluten-related conditions and those without.
Dr Ruhl's team concludes, "In the US population, a higher proportion of persons living at latitudes of 35° North or greater have celiac disease or avoid gluten than persons living south of this latitude, independent of race or ethnicity, socioeconomic status, or body mass index."
"Mean levels of vitamin B-12 and folate are lower in individuals with undiagnosed celiac disease, and levels of hemoglobin are lower in participants with a diagnosis of celiac disease, compared with individuals without celiac disease."