Inflammatory bowel disease: causes
Inflammatory bowel disease (IBD) is a growing disease of an unknown cause whose incidence continues to grow throughout the world. However, IBD is not very common in children. Only between 15 and 25% of cases are diagnosed before the age of 20.
Some hypotheses suggest that lifestyle changes may play an important role in the appearance of this type of disease.
In this sense, in addition to genetic factors, environmental factors are involved in the risk of pediatric IBD, related to changes in the intestinal flora and the immune system.
IBD environmental factors
Some environmental factors that increase the risk of IBD include:
Reside in the high latitude (more risk the further north).
Live in an urban environment.
Have a high socio-economic status.
Present an excess of cleaning or lack of exposure to non-pathological enteric microorganisms during childhood.
Exposure to tobacco smoke.
Different types of IBD
The two main types of IBD, Crohn’s disease and ulcerative colitis have different clinical features and possibly different causes.
In USA, an estimated 60,000 people suffer from ulcerative colitis and about 40,000 have Crohn’s disease.
The incidence of pediatric Crohn’s disease increases as we move away from the equator, at least in the northern hemisphere. This is directly associated with a greater number of months in which the sun’s ultraviolet radiation does not exceed a certain threshold (specifically 1,488 kJ per square meter).
Sun exposure and childhood inflammatory bowel disease
The findings of various studies suggest the existence of a relationship between the incidence of childhood IBD and exposure to ultraviolet radiation or an associated factor such as vitamin D level. To date, there were no studies that investigated at the individual level whether increased sun exposure was associated with a reduced risk of IBD.
Case-control study on sun exposure and childhood inflammatory bowel disease
The study, carried out by various Australian research centers and recently published in the Journal of Pediatric Gastroenterology and Nutrition, investigated sun exposure at the individual level and the risk of initiating IBD in children up to 18 years of age who lived in the city of Melbourne, Australia.
For this, 99 children from 0 to 17 years of age diagnosed with IBD were recruited using clinical, histological, and radiological criteria.
The members of the control group, 396 in total, were also from 0 to 17 years old and had been born in the state of Victoria, Australia. They did not have a diagnosis of IBD or any related disease. They also had no family history of the disease.
Sun exposure was measured with various questionnaires, taking into account the season of the year, weekends, and holidays in the different age stages (0-2 years; 3-5 years; 6-10 years; 11-15 years) and the time of exposure to the sun in the last summer and winter.
The results of the study showed that Crohn’s disease was the most diagnosed IBD in the group of cases (63.9%).
The study found that a slight increase in sun exposure on weekends and summer or winter vacations (10 extra minutes) was associated with a 6% reduction in the risk of inflammatory bowel disease.
The association showed a linear relationship. In addition, getting a darker skin tone after 2 weeks of vacation was found to be associated with a lower risk of IBD. The association became stronger with increasing age, reflecting a possible cumulative effect.
These results support the idea of a protective effect of sun exposure in the development of childhood IBD. Furthermore, the results are consistent with previous ecological studies but do not show possible causes.
In this sense, the immune modulation that would reduce the risk of IBD could occur through the improvement of vitamin D levels induced by sun exposure. However, it could also take place through other modifications after skin exposure to UV rays.
In any case, it is not clear whether vitamin D deficiency may be the cause or a consequence of the disease, and the disparate results of studies with vitamin D supplements have not resolved the question.
The study under review adds to growing evidence that increased sun (or vitamin D) exposure is associated with a reduced risk of some autoimmune diseases. In any case, the increased risk of some types of skin cancer, such as melanoma, after sun exposure should not be forgotten either.
In conclusion, it may be that changes in children’s behavior concerning their relationship with the environment (less playing in the street, less exposure to the sun, and more staying indoors) could be related to the causes of the increase in some diseases, as is the case with inflammatory bowel disease.