In Sweden, celiac disease occurs in 1.8% of the population, which is almost double the rate in the rest of the world (1%).1 While many studies have concentrated on genetics and early infections as factors influencing Sweden’s high prevalence rate, a new study suggests that disease risk might be linked to the seasons and birth location.
Using data from almost two million Swedish children born between 1991 and 2009, researchers found that those who are born in the spring, summer, and fall had about an 8-10% increased risk for developing celiac disease when compared to winter babies.2 They also found that children born in southern and central Sweden had an increased celiac risk compared to those in the northern region. Combining regional data with birth month and season, children born in southern Sweden during March, April, and May have the highest risk.
At this stage, researchers have no firm explanations for the differences. They hypothesize that children born in spring and summer tend to be weaned and introduced to gluten in the fall and winter, right at the time that viral infections begin circulating through the population. If contracted, these viruses could influence a child’s gut bacteria and alter the intestinal lining, laying a foundation for celiac disease. Moreover, seasonal viruses can take months to travel from the southern regions to the north; the study’s authors believe this could explain why the incidence of celiac disease is lower for northern toddlers.
This study will likely inspire researchers in other countries to analyse the effects of environmental factors on celiac disease in their own populations. Since Sweden is already a northern country, it will be interesting to see what impact climate has on celiac disease risk. As environmental factors are identified and assessed, researchers hope one day to be able to adapt behaviour to prevent the gradual increase in celiac disease occurring worldwide.