A recent editorial helps provide some answers and even explains the term “protopathic bias.” Ostensibly, the editorial’s task is to explain the potential interaction of maternal serum iron ingestion and the risk of celiac disease (see previous blog post: Is There a Link Between Maternal Iron Supplementation and …). However, the editorial provides an explanation for the Swedish epidemic and the ongoing slower, wider epidemic.
Here’s the link, http://ow.ly/vQGQ7, and here’s an excerpt:
The Swedish epidemic of CD of 1985–1994 has been extensively documented, and resulted in the development of hypotheses regarding environmental risk factors for this disorder.7 This epidemic was restricted to children younger than 2 years; in that age group, the incidence of diagnosed CD rose from 65 cases per 100,000 person-years to 198 cases per 100,000 person-years. In contrast, incidence data for older children were relatively flat during this period. The epidemic abruptly ended in 1995, although children born during the period of the epidemic have an ongoing increased risk of developing CD. Subsequent investigation led to the hypothesis that infant feeding practices affect the risk of CD in young children. The epidemic occurred during a period of relatively low rates of breastfeeding at the age of 6 months and during the same period of time, the quantity of gluten in infant formula greatly increased. Although it is difficult to separate the relative importance of each feeding practice, it seemed that high quantity of initial gluten intake without overlapping with breastfeeding was responsible for this epidemic. Although a systematic review of the issue has concluded that breastfeeding has not been definitively proved to be associated with risk of CD,8 subsequent research has indicated that the timing of gluten introduction is important in determining risk.9PreventCD, a prospective randomized trial of infants with a family history of CD, is testing specifically whether the introduction of small quantities of gluten beginning at age 4 months of age will induce tolerance to gluten in this high-risk group.
The second epidemic is more diffusely spread over time and space. Studies from the United States and elsewhere have shown that the seroprevalence of CD (as defined by positive tissue transglutaminase and endomysial antibodies) has increased markedly in recent decades. An analysis of stored serum from military recruits at the Warren Air Force Base in the years spanning 1948–1954 found a CD seroprevalence of 0.2%, whereas 2 recent cohorts from Olmsted County (spanning the years 2006–2008) matched by year of birth and age at sampling found a seroprevalence of 0.9% and 0.8%, respectively.11 An analysis of another cohort in this country found a doubling in seroprevalence during adulthood from 1974 (0.21%) to 1989 (0.45%).12 The mode of presentation of CD has changed in the past generation, with rising numbers of patients presenting without diarrhea.13 Patients presenting with anemia may have more severe disease expression (as measured by the degree of villous atrophy and the presence of metabolic bone disease) than patients presenting with diarrhea.14 Because most individuals in the United States with CD are undiagnosed,15 this is largely a hidden epidemic, but there is no reason to believe that the prevalence has peaked. In Finland, which had a higher prevalence of CD than the United States to begin with, the seroprevalence of CD doubled between the years 1978 (1.05%) and 2000 (1.99%).16 It is not known whether this epidemic will subside or if the prevalence of CD will continue to rise to a new set-point. But given the morbidity associated with CD17 and the cost and difficulty of the gluten-free diet18, 19 these data have sparked interest in identifying the cause of this less visible epidemic.
Certain infections (eg, rotavirus among infants20 and Campylobacter among adults21) have recently been shown to be associated with a increased risk of CD, but rates of these infections have not increased markedly, and so are not likely to be driving this epidemic. In contrast, a lack of exposure to certain microbes is a hallmark of modern times, and the increase in CD disease is congruent with the hygiene hypothesis, which states that decreased exposure to microbes may be driving the rise in autoimmune and atopic conditions. This hypothesis is particularly compelling in light of a recent study that found a dramatically different seroprevalence of CD in Finland (1.4%) and the Russian Karelia (0.6%), geographically proximate areas with a similar prevalence of HLA DQ2 and DQ8 but with major differences in economic development.22
Further evidence implicating the modern relationship with microbes is now accumulating. Children who were born by elective cesarean section are at increased risk of developing CD, whereas those born by emergent cesarean section (and may have had contact with the birth canal) are not.23 In addition, there seems to be an inverse relationship between Helicobacter pylori colonization and CD.24 Drugs are another modern innovation that may be affecting the CD epidemic. Population-based studies from Sweden have shown that prescription of antibiotics25 and proton pump inhibitors26 are each associated with an increased risk of the subsequent development of CD.
The associations identified in these studies are not necessarily causal. Studies of drug exposure in particular may be prone to protopathic bias, wherein early symptoms of the outcome of interest (CD) may lead to the prescription of the exposure (eg, antibiotics or proton pump inhibitors).
From the NY Times: Gluten-free, veggie snacks, vegan desserts, spring salads. They’re all in our new recipe finder. http://nyti.ms/1m5K7oE