A recent study (CN Bernstein et al. Gastroenterol 2019; 156: 2190-7; editorial 2124) delves into the topic of early life risk factors for the development of IBD. In the background, the author note that in 2018, 267,983 Canadians (0.73%) were estimated to be living with IBD and there is a forecast that this will increase to 402,853 by 2030.
This study used a Manitoba database and examined the records of individuals diagnosed with between 1984-2010. In addition, they correlated this data with individual data of the postnatal period between 1970-2010. From this database, they analyzed 825 individuals with IBD and 5999 matched controls.
- The strongest risk factor for the development of IBD was a maternal diagnosis of IBD with an odds ratio (OR) of 4.53; the OR was higher for CD at 5.98 compared to OR of 2.71 for UC
- Infections in the first year of life was associated with an OR of 3.06 for IBD diagnosed before age 10 years, and OR of 1.63 for IBD diagnosis before age 20 years. Only infections in the first year of life were correlated with IBD as infections during the first 3 years of life were not associated with a significant increased risk.
- While infections in the first year of life were associated with an increase risk of IBD, the authors could not demonstrate that individuals who developed IBD had more infections than unaffected sibling controls (though they did have more infections than the entire control cohort).
- Highest socioeconomic quintile, also, had an increased OR of 1.35.
- Gastrointestinal illnesses (like abdominal pain) were not found to be associated with the later development of IBD.
It is unclear whether infections in early life increase the risk of IBD or whether other factors like antibiotics contribute to the higher rate of IBD. The authors did not find more immunodeficiency disorders in the IBD cohort compared to controls.
My take: This study identified genetic risk as substantially greater than specific environmental risks. However, the increasing incidence of IBD suggests that environmental factors are quite significant, as genetic risk factors are less likely to change enough to account for the changes in epidemiology. As such, there are a few explanations:
- There are other unidentified environment risk factors
- Some individuals are more susceptible to the changes that have occurred in the environment; that is, their environmental exposures are not significantly different from their peers but are significantly different than individuals from 20, 40, 60 and 100 years ago.
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