In a recent study published in eClinicalMedicine, researchers examined the impact of environmental exposures in early life on the risk of inflammatory bowel disease (IBD), ulcerative colitis (UC), and Crohn’s disease (CD).
Study: Association between early life exposure to agriculture, biodiversity, and green space and risk of inflammatory bowel disease: a population-based cohort study. Image Credit: Katya Shut/Shutterstock.com
Background
The prevalence of IBD and its subtypes (UC and CD) has increased worldwide. IBD poses a significant burden to individuals, society, and healthcare systems. Yet, its risk factors and mechanisms remain unclear. IBD emergence in the West and recently industrialized nations has occurred in parallel with the urbanization/loss of the natural environment.
Studies have shown the protective effects of blue and green spaces against IBD. Nevertheless, the impact of relevant exposures, including biodiversity and agricultural land use, in early life on IBD is unknown.
Given the rapid loss of natural environments due to biodiversity and climate crises, understanding the role of environmental exposure in health and disease is essential.
About the study
In the present study, researchers investigated the role of environmental exposures in early life on the risk of IBD. They included people born in Denmark between January 1, 1995, and August 1, 2018, who were Danish residents for ≥ two years post-birth and whose mothers were also residents during pregnancy.
Environmental exposure variables were biodiversity, agricultural land use, blue space, green space, urban space, and normalized difference vegetation index (NDVI).
Each offspring was assigned an exposure value for their residential municipality during an exposure window from pregnancy until two years post-birth.
In cases where participants’ residential municipality changed during this window, a weighted average was assigned for the municipalities. CORINE Land Cover Inventory, with 44 land cover classes and a minimum mapping unit of 25 hectares, was used as the data source for land cover.
Each unit was categorized as green space, water bodies, agricultural land, or urban space. Green space was the proportion of land classified as forest or natural/urban green areas.
Agricultural land use was the proportion of municipal land (excluding water bodies) classified as agricultural areas. The bioscore, a measure of local flora and fauna, was used to define the biodiversity.
Urban space was the proportion of the municipal land covering urban areas, excluding green urban areas. Blue space was the proportion of the municipal land within 600 meters of a water body, equivalent to a 10-minute walking distance.
The NDVI was determined by comparing light reflectance in the red and near-infrared spectra.
All participants were followed from two years post-birth until the diagnosis of IBD, death, emigration, or September 1, 2020.
Each exposure was categorized into quartiles, with the lowest being the reference. Cox proportional hazard regression was used to investigate associations between exposures and primary (IBD) and secondary outcomes (UC and CD).
Findings
Overall, of more than 1.51 million people born in Denmark during the specified period, the researchers included > 1.4 million individuals. IBD was diagnosed in 3,768 subjects.
IBD and non-IBD participants were followed up until a median age of 17 and 14, respectively. The third quartile of agricultural land use was associated with higher IBD risk than the reference quartile.
The third quartile of biodiversity was associated with a lower IBD risk than the reference. No associations were observed for blue space, urban space, green space, and NDVI.
Further, CD risk among those exposed to the highest, second, or third quartiles of agricultural land use was higher than those in the lowest quartile. The third biodiversity quartile was associated with a lower CD risk than the reference.
The highest green space quartile was associated with a higher risk of CD than the reference. There were no associations between quartiles of other environmental variables and CD risk.
In addition, the third green space quartile was associated with the risk of UC; no associations were observed between the remaining exposures and UC risk.
Conclusions
Taken together, early life exposure to agricultural land use increased CD risks, whereas exposures to green space and biodiversity were protective against IBD. The team found no conclusive impact of early-life environmental exposures on the risk of UC.
Further, there were no associations between blue space, urban space, or NDVI and the risks of CD and UC.
Besides, the findings remained consistent across varying definitions of exposures, underscoring their robustness.
Scientists uncover two Crohn’s disease subtypes using lab-grown intestines, offering hope for personalized therapies