Quantifying the Risk of Autoimmunity for Celiac Disease

A recent study (MR Khan et al. JPGN 2019; 69: 438-42) examined the rates of autoimmune disorders (AD) among patients with celiac disease (CD) (n=249) compared to a control group (n=498) over an 18 year period (1997-2015). The authors utilized the  a database of medical records via the Rochester Epidemiology Project (Mayo Clinic/Olmstead County).

Key findings:

  • Five years after the index date, 5.0% of CD patients and 1.3% of controls had a de novo AD diagnosis
  • In the pediatric age group, there was an increased risk of AD: 5/83 (7.3%) of CD patients and 0/179 (0%) developed a AD diagnosis at the 5-year mark
  • The authors note that they observed a lower rate of Hashimoto thyroiditis after the diagnosis of CD, likely indicating a protective role of a gluten-free diet
  • Thyroid disorders, type 1 DM, psoriasis/psoriatic arthritis and rheumatoid arthritis were the most common AD identified in patients with CD

Limitations:

  • Retrospective study
  • Adherence with GFD was not assessed

My take: Screening for AD periodically is worthwhile in patients with CD, particularly thyroid disorders and type 1 diabetes which accounted for ~80% of the autoimmune conditions identified.

Briefly noted: R Ahawat et al. JPGN 2019; 69: 449-54. In this study with 38 newly-diagnosed CD, the authors found a high prevalence of low vitamin D (25OHD) levels (65.8%) -defined as <30 ng/mL; however, the control population had a higher rate of 79.3%.  While the authors advocate checking vitamin D levels due to the risk of bone disease, it is noted that bone mineral density and vitamin deficiencies frequently improve with a gluten-free diet (Related post: Celiac studies)

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Northern Latitudes -Higher Prevalence of Celiac Disease and Gluten Avoidance

A recent study (A Unalp-Arida et al. Gastroenterol 2017; 152: 1922-32) examines the relationship of latitude and the prevalence of celiac disease and gluten avoidance.

Using the NHANES 2009-2014 survey with 22,277 participants (6 years and older), the authors identified persons with celiac disease (based on serology) along with those who avoided gluten without a diagnosis of celiac disease.

Key findings:

  • 0.7% of participants had celiac disease and 1.1% avoided gluten without celiac disease
  • Celiac disease was more common among individuals who lived at latitudes of above 35 degrees and more common with higher socioeconomic status. Figure 2 map provides latitude lines. In the eastern U.S. the Georgia-Tennessee border corresponds to this latitude line and in the western U.S. the southern tip of Nevada lies on this line.
  • From 35 degrees to 39 degrees the odds ratio was 3.2, whereas the odds ratio was 5.4 for those above 40 degrees.  These odds ratios were independent of race, ethnicity, socioeconomic status and body mass index.
  • Similarly, the prevalence of gluten avoidance without celiac disease was twice as common among persons living north of 40 degrees compared with those residing at latitudes <35 degrees.
  • The findings on latitude were heavily influenced by the increased rate of celiac and gluten avoidance in the Northeast region (more so than in the West)

In their discussion, the authors note that “a North-South gradient in disease occurrence in genetically similar populations has been shown in studies of autoimmune diseases, including inflammatory bowel disease, multiple sclerosis, and rheumatoid arthritis.” Potential environmental factors could include lack of sunshine/vitamin D deficiency, hygiene, and infections.  A study comparing similar populations in Finland and Russia suggested a lower economic status/less hygiene increased the risk of celiac disease despite similar gluten exposure.  The authors note that there was NOT an increased risk in Northern Sweden compared to Southern Sweden.  In fact, this study of children found a higher rate of celiac disease in Southern Sweden (Arch Dis Child 2016; 101: 1114-18).

My take: This is another intriguing study regarding celiac disease epidemiology which strongly points to environmental factors accounting for marked variation in celiac disease prevalence.

More information on this topic from AGA Blog: Do More People Have Celiac Disease in the North vs the South?

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Timing of Solid-Food Introduction

The “DAISY” (diabetes autoimmunity  study in the young) study indicates that the timing of solid-food introduction can influence the likelihood of developing type 1 diabetes (T1DM) (JAMA Pediatr 2013; 167: 808-15).

The participants were 1853 children at increased genetic risk for T1DM who were enrolled in a longitudinal observational cohort study in Denver. Early solid-food exposure was considered <4 months of age and late >6 months of age.

Results:

  • “Both early and late first exposure to any solid food predicted development of T1DM.”  For early exposure, the Hazard Ratio was 1.91 and for late HR was 3.02.
  • Breastfeeding at the time of introduction to wheat/barley conferred protection (HR 0.47)

The study has several limitations, particularly the relatively low numbers of children who developed T1DM (n=53).

A second study (Pediatrics 2013 [doi: 10.1542/peds2012-3692]) –thanks to Ben Gold for this reference –showed that “solid foods were introduced significantly earlier among the infants with allergies, with 35% of them receiving their first solids before and including 16 weeks, compared with 14% of control infants (P=.011).”   (Solid foods before 17 weeks linked to food allergy)

Bottomline: As with celiac disease (GlutenRelated Disorders” (Part 1) | gutsandgrowth), current science suggests the introduction of solid foods between 4-6 months of age may diminish the risk of developing T1DM as well as food allergies.