Background: As inflammatory bowel disease (IBD) might be associated with environmental factors such as seasonal patterns and low vitamin D levels we aimed to assess their association with IBD onset and flares in a large cohort of children.
Methods: The records of 623 pediatric onset IBD patients were reviewed retrospectively including age at onset, gender, severity indices, month of first symptom, and vitamin D levels at diagnosis. For a subgroup of patients, data included date of first flare and vitamin D levels during flare and remission.
Results: Median age at diagnosis was 14 years (IQR 11.66-15.58). Disease onset did not vary significantly between either month (P=0.367) or seasons (P=0.460). Vitamin D deficiency at the time of diagnosis was prevalent in 21% of patients with no significant association with month, season or disease's type. Vitamin D deficiency was significantly more prevalent in patients with malnutrition (P<0.001) and was associated with hypoalbuminemia (P=0.02) but did not correlate with low bone mineral density. Analysis of 169 first flares showed that flares were more common in June and less common in April (P=0.016). Mean vitamin D level was significantly lower during flares compared with remission (55.25±19.28 vs. 64.16±26.6, respectively, P=0.012).
Conclusions: IBD onset in school aged children is not associated with seasonal patterns whereas flares may follow a specific monthly pattern. Disease flares are associated with low vitamin D blood levels. Vitamin D deficiency is associated with malnutrition and hypoalbuminemia.