Month of birth may be linked to risk of Crohn's disease later in childhood, concludes a study in this week's BMJ.
Researchers in Denmark identified 627 cases of Crohn's disease from 1977 to 1992 in people aged less than 21. They found that the peak in births occurred in August and the trough in March.
Previous studies have suggested that exposure to certain infections before birth or in early childhood are important risk factors. Therefore, if infectious agents potentially linked to Crohn's disease include some that are common at particular times of year, their seasonal variation might be reflected in the pattern of birth month in people with Crohn's disease, explain the authors.
These findings contrast with a recent British study, that reported slightly increased risk of Crohn's disease in people born in the first half of the year, not the second half. However, if causal factors differ in the two countries, this might result in different seasonal patterns, they conclude.