Is Long-term Ambient Air Pollutant Exposure a Risk Factor for Irritable Bowel Syndrome in Children? A 12-year Longitudinal Cohort Study

A systematic review of the association between environmental risk factors and the development of irritable bowel syndrome

BACKGROUND AND AIM

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder with roots in genetic, immune, psychological, and dietary factors. Recently, the potential correlation between environmental exposures, such as air pollution, and IBS has gained attention. This review aimed to systematically examine existing studies on environmental factors associated with IBS, elucidating this interplay and guiding future research.

METHODS

A literature search was conducted in Medline, EMBASE, Scopus, and Cochrane databases from database inception to October 10, 2023, using the keywords "Irritable Bowel" or IBS or "Irritable Colon" or "Mucous Colitis" or "Spastic Colitis" or "Spastic Colon" AND "environment* exposure*". Studies were included if they were original, published in English, described defined environmental exposure(s), and had documented diagnosis of IBS. For the purposes of this review, articles reporting physical (e.g. radiation and climate change), biological (e.g. bacteria and viruses), and chemical (e.g. harmful gases) exposures were included while psychological and dietary factors, which have been reviewed in detail elsewhere, are outside of the scope.

RESULTS

A total of seven studies focusing on air quality, microbial exposure, and other environmental factors were reviewed. Studies highlighted a potential association between air pollutants and increased IBS incidence. Microbial exposure, post-natural disaster or due to poor sanitation, was linked to IBS development and gut dysbiosis. Other exposures, such as early pet ownership, were also associated with IBS risk.

CONCLUSION

Existing research demonstrates an epidemiologic relationship between environmental exposures and the development of IBS. Further research is needed to understand these associations.

The Impact of Climate Change, Pollution, and Biodiversity Loss on Digestive Health and Disease

The environment is changing rapidly under pressure from 3 related drivers: climate change, pollution, and biodiversity loss. These environmental changes are affecting digestive health and disease in multiple ways. Heat extremes can cause intestinal and hepatic dysfunction. Access to adequate amounts of food of high nutritional content and to clean water is under threat. Extreme weather is associated with flooding and enteric infections and affects the delivery of care through infrastructure loss. Air, water, and soil pollution from chemicals and plastics are emerging as risk factors for a variety of intestinal diseases including eosinophilic esophagitis, metabolic dysfunction associated fatty liver disease, digestive tract cancers, inflammatory bowel disease, and functional bowel disease. Migration of populations to cities and between countries poses a special challenge to the delivery of digestive care. The response to the threat of environmental change is well underway in the global digestive health community, especially with regard to understanding and reducing the environmental impact of endoscopy. Individuals, and peer societies, are becoming more engaged, and have an important role to play in meeting the challenge.

Associations between air pollution and multimorbidity in the UK Biobank: A cross-sectional study

Background

Long-term exposure to air pollution concentrations is known to be adversely associated with a broad range of single non-communicable diseases, but its role in multimorbidity has not been investigated in the UK. We aimed to assess associations between long-term air pollution exposure and multimorbidity status, severity, and patterns using the UK Biobank cohort.

Methods

Multimorbidity status was calculated based on 41 physical and mental conditions. We assessed cross-sectional associations between annual modeled particulate matter (PM)2.5, PMcoarse, PM10, and nitrogen dioxide (NO2) concentrations (μg/m3-modeled to residential address) and multimorbidity status at the baseline assessment (2006-2010) in 364,144 people (mean age: 52.2 ± 8.1 years, 52.6% female). Air pollutants were categorized into quartiles to assess dose-response associations. Among those with multimorbidity (≥2 conditions; n = 156,395) we assessed associations between air pollutant exposure levels and multimorbidity severity and multimorbidity patterns, which were identified using exploratory factor analysis. Associations were explored using generalized linear models adjusted for sociodemographic, behavioral, and environmental indicators.

Results

Higher exposures to PM2.5, and NO2 were associated with multimorbidity status in a dose-dependent manner. These associations were strongest when we compared the highest air pollution quartile (quartile 4: Q4) with the lowest quartile (Q1) [PM2.5: adjusted odds ratio (adjOR) = 1.21 (95% CI = 1.18, 1.24); NO2: adjOR = 1.19 (95 % CI = 1.16, 1.23)]. We also observed dose-response associations between air pollutant exposures and multimorbidity severity scores. We identified 11 multimorbidity patterns. Air pollution was associated with several multimorbidity patterns with strongest associations (Q4 vs. Q1) observed for neurological (stroke, epilepsy, alcohol/substance dependency) [PM2.5: adjOR = 1.31 (95% CI = 1.14, 1.51); NO2: adjOR = 1.33 (95% CI = 1.11, 1.60)] and respiratory patterns (COPD, asthma) [PM2.5: adjOR = 1.24 (95% CI = 1.16, 1.33); NO2: adjOR = 1.26 (95% CI = 1.15, 1.38)].

Conclusions

This cross-sectional study provides evidence that exposure to air pollution might be associated with having multimorbid, multi-organ conditions. Longitudinal studies are needed to further explore these associations.

Identification of putative transcriptomic biomarkers in irritable bowel syndrome (IBS): Differential gene expression and regulation of TPH1 and SERT by vitamin D

Irritable bowel syndrome (IBS) is one of the most common gastrointestinal disorders and affects approximately 4% of the global population. The diagnosis of IBS can be made based on symptoms using the validated Rome criteria and ruling out commonly occurring organic diseases. Although biomarkers exist for "IBS mimickers" such as celiac disease and inflammatory bowel disease (IBD), no such test exists for IBS. DNA microarrays of colonic tissue have been used to identify disease-associated variants in other gastrointestinal (GI) disorders. In this study, our objective was to identify biomarkers and unique gene expression patterns that may define the pathological state of IBS. Mucosal tissue samples were collected from the sigmoid colon of 29 participants (11 IBS and 18 healthy controls). DNA microarray analysis was used to assess gene expression profiling. Extraction and purification of RNA were then performed and used to synthesize cDNA. Reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) was employed to identify differentially expressed genes in patients diagnosed with IBS compared to healthy, non-IBS patient-derived cDNA. Additional testing probed vitamin D-mediated regulation of select genes associated with serotonergic metabolism. DNA microarray analyses led to the identification of 858 differentially expressed genes that may characterize the IBS pathological state. After screening a series of genes using a combination of gene ontological analysis and RT-qPCR, this spectrum of potential IBS biomarkers was narrowed to 23 genes, some of which are regulated by vitamin D. Seven putative IBS biomarkers, including genes involved in serotonin metabolism, were identified. This work further supports the hypothesis that IBS pathophysiology is evident within the human transcriptome and that vitamin D modulates differential expression of genes in IBS patients. This suggests that IBS pathophysiology may also involve vitamin D deficiency and/or an irregularity in serotonin metabolism.

Environmental Pollutants Are Associated With Irritable Bowel Syndrome in a Commercially Insured Cohort of California Residents

BACKGROUND AND AIMS

Prior studies have linked environmental pollutants with gastrointestinal (GI) diseases. Here, we quantify the relationships between 7 pollutants and the zip code-level incidence of irritable bowel syndrome (IBS), functional dyspepsia, inflammatory bowel diseases (IBDs), and eosinophilic esophagitis (EoE) in California.

METHODS

Claims in Optum's Clinformatics Data Mart were linked with environmental exposures in California, derived from CalEnviroScreen 3.0. We identified adult patients with new diagnoses of each GI disease, and estimated claims-derived, zip code-level disease incidence rates. Two study periods were considered: 2009-2014 (International Classification of Diseases-Ninth Revision era) and 2016-2019 (International Classification of Diseases-Tenth Revision [ICD-10] era). Multivariable negative binomial regression models were used to test associations between 7 pollutants (ozone, particulate matter <2.5 μm [PM2.5], diesel emissions, drinking water contaminants, pesticides, toxic releases from industrial facilities, traffic density) and zip code-level incidence of the GI diseases along with a negative control outcome, adjusting for numerous potential confounders.

RESULTS

Zip code-level IBS incidence was associated with PM2.5 (P < .001 in both eras) and airborne toxic releases from facilities (P < .001 in both eras). An increase of 1 μg/m³ in PM2.5 or 1% in toxic releases translates to an increase in the IBS incidence rate of about 0.02 cases per 100 person-years. Traffic density and drinking water contaminant exposures were also associated with increasing IBS incidence, but these associations were not significant in both eras. Similarly, exposure to PM2.5, drinking water contaminants and airborne toxic releases from facilities were associated with functional dyspepsia incidence, though not in both eras. No significant associations were noted between pollutants and IBD or EoE incidence.

CONCLUSION

Exposure to PM2.5 and airborne toxic releases from facilities are associated with higher IBS incidence among a cohort of commercially insured Californians. Environmental pollutant exposure was not associated with the incidence of IBDs and EoE in this cohort.

Probiotics, prebiotics, and synbiotics to prevent or combat air pollution consequences: The gut-lung axis

Air pollution exposure is a public health emergency, which attributes globally to an estimated seven million deaths on a yearly basis We are all exposed to air pollutants, varying from ambient air pollution hanging over cities to dust inside the home. It is a mixture of airborne particulate matter and gases that can be subdivided into three categories based on particle diameter. The smallest category called PM_0.1 is the most abundant. A fraction of the particles included in this category might enter the blood stream spreading to other parts of the body. As air pollutants can enter the body via the lungs and gut, growing evidence links its exposure to gastrointestinal and respiratory impairments and diseases, like asthma, rhinitis, respiratory tract infections, Crohn's disease, ulcerative colitis, and abdominal pain. It has become evident that there exists a crosstalk between the respiratory and gastrointestinal tracts, commonly referred to as the gut-lung axis. Via microbial secretions, metabolites, immune mediators and lipid profiles, these two separate organ systems can influence each other. Well-known immunomodulators and gut health stimulators are probiotics, prebiotics, together called synbiotics. They might combat air pollution-induced systemic inflammation and oxidative stress by optimizing the microbiota composition and microbial metabolites, thereby stimulating anti-inflammatory pathways and strengthening mucosal and epithelial barriers. Although clinical studies investigating the role of probiotics, prebiotics, and synbiotics in an air pollution setting are lacking, these interventions show promising health promoting effects by affecting the gastrointestinal- and respiratory tract. This review summarizes the current data on how air pollution can affect the gut-lung axis and might impact gut and lung health. It will further elaborate on the potential role of probiotics, prebiotics and synbiotics on the gut-lung axis, and gut and lung health.

How to manage irritable bowel syndrome in children

AIM

This paper discusses the risk factors and management of paediatric irritable bowel syndrome (IBS), with a focus on the role of the gastrointestinal microbiome.

METHODS

English articles of interest published in PubMed and Google Scholar were searched using subject heading and keywords of interest.

RESULTS

Only few randomised controlled trials on the management of IBS in children have been published. The vast majority of these intervention trials target to change the composition of the gastrointestinal microbiome. Most studies are underpowered. Major heterogeneities in study designs such as differences in inclusion criteria, including patients with different pain-related functional gastrointestinal disorders and differences in primary outcomes, make it impossible to formulate recommendations. Overall, few adverse events are reported what could indicate safety or point to suboptimal conduction of clinical trials and safety reporting. However, it can also not be excluded that some interventions such as the administration of selected probiotic products may result in benefit.

CONCLUSION

There is insufficient evidence to recommend any therapeutic intervention in paediatric IBS, including manipulation of the gastrointestinal tract microbiome, despite the evidence that dysbiosis seems an associated pathophysiologic factor. More designed prospective trials are needed since IBS is not a rare condition during childhood.

Review article: Epidemiological and animal evidence for the role of air pollution in intestinal diseases

BACKGROUND

Ambient air pollution is recognized as one of the leading causes of global burden of disease. Involvement of air pollution in respiratory and cardiovascular diseases was first recognized, and then cumulative data has indicated that the intestinal tract could be also damaged.

AIM

To review and discuss the current epidemiological and animal data on the effects of air pollution on intestinal homeostasis.

METHODS

An extensive literature search was conducted using Google Scholar and Pubmed to gather relevant human and animal studies that have reported the effects of any air pollutant on the intestine.

RESULTS

Exposure to several gaseous and particulate matter components of air pollution have been associated either positively or negatively with the onset of various intestinal diseases including appendicitis, gastroenteric disorders, irritable bowel syndrome, inflammatory bowel diseases, and peptic ulcers. Several atmospheric pollutants have been associated with modifications of gut microbiota in humans. Animal studies have showed that inhalation of atmospheric particulate matter can lead to modifications of gut microbiota, impairments of oxidative and inflammatory intestinal balances, and disruption of gut epithelial permeability.

CONCLUSIONS

Overall, the literature appears to indicate that the gut is an underestimated target of adverse health effects induced by air pollution. It is therefore important to develop additional studies that aim to better understand the link between air pollutants and gastro-intestinal diseases.

Parental, Perinatal, and Childhood Risk Factors for Development of Irritable Bowel Syndrome: A Systematic Review

Background/Aims

Adverse early life experiences are associated with the development of stroke, cancer, diabetes, and chronic respiratory and ischemic heart diseases. These negative experiences may also play a role in the development of irritable bowel syndrome (IBS)--a functional gastrointestinal disease. This review discusses the research to date on the parental, perinatal, and childhood risk and protective factors associated with the development of IBS.

Methods

A literature search was completed for studies published between 1966 and 2018 that investigated premorbid factors occurring during the perinatal and childhood periods as well as parental factors that were associated with the development of IBS.

Results

Twenty-seven studies fulfilled the review criteria. Risk factors that appeared in more than one study included: (1) parental IBS, substance abuse, parental punishment, and rejection as parental risk factors; (2) low birth weight as a perinatal risk factor; and (3) crowded living conditions in low-income families, childhood anxiety, depression, or child abuse as childhood risk factors. Protective factors for IBS were emotional warmth from the parents and being born to an older mother.

Conclusions

More effort is needed to identify what fetal and maternal factors are associated with low birth weight and IBS. A well-executed prospective birth cohort with a collection of bio-samples and functional data will provide a better understanding of how adversity and the interplay between genetics, epigenetics, and numerous risk factors affect the development of IBS.

Risk of irritable bowel syndrome in patients who underwent appendectomy: A nationwide population-based cohort study

BACKGROUND

Appendectomy is one of the most common surgical procedures; however, the possible long-term consequences have not been fully explored. The appendix has been associated with microflora of the gut and immune functions. However, literature examining the relationship between prior appendectomy and the risk of irritable bowel syndrome (IBS) is lacking. The aim of this study was to evaluate the risk of irritable bowel syndrome for patients who underwent appendectomy by using a nationwide longitudinal population-based cohort.

METHODS

Data from this study was collected from Taiwan's National Health Insurance Research Database (NHIRD), a population-based database. We identified 12,760 patients who underwent appendectomy between January 1, 2000 and December 31, 2012. A total of 9236 patients who had appendectomy (case group) were randomly matched with 9236 patients who had not undergone appendectomy (control group) in a ratio of 1:1 by means of propensity scores. The hazard ratio (HR) of IBS was calculated by multiple Cox regression. Furthermore, sensitivity test and stratified analysis were performed.

FINDINGS

The incidence rate of IBS was 51.30 per 10,000 person-years in patients having appendectomy, more than the 35.28 per 10,000 person-years in patients not having appendectomy. Patients who underwent appendectomy had 1.46-fold risk of IBS compared to patients not having appendectomy (HR, 1.46; 95% CI, 1.24-1.72). Stratified analysis revealed that the higher HR of 1.55 (95% CI, 1.18-2.04) in patients <40 years old, and particularly within the first 5 years follow-up period of undergoing appendectomy. In addition, patients diagnosed with fibromyalgia had a greater risk of suffering IBS after appendectomy (HR, 1.41; 95% CI, 1.04-1.92).

INTERPRETATION

Patients with appendectomy have a higher incidental risk of IBS than the control population. The risk is higher for patients under 40 years old and those who received appendectomy within 5 years. Physicians could take this into consideration for treatment plans of patients who have underwent this surgery. Further research on the pathogenesis of this association is required.

FUNDING

This work was supported by grants from the Ministry of Health and Welfare, Taiwan (MOHW108-TDU-B-212-133004), China Medical University Hospital, Academia Sinica Stroke Biosignature Project (BM10701010021), MOST Clinical Trial Consortium for Stroke (MOST 108-2321-B-039-003-), Tseng-Lien Lin Foundation, Taichung, Taiwan, and Katsuzo and Kiyo Aoshima Memorial Funds, Japan.

Association between Irritable Bowel Syndrome and Allergic Diseases: To Make a Case for Aeroallergen

Irritable bowel syndrome (IBS) is a functional gastrointestinal disease and the most common cause of prolonged abdominal pain and bowel disturbances in the developed world. While initially thought to be functional or psychosomatic in nature, IBS is now recognized as a heterogeneous group of conditions. A subset of IBS patients and patients with allergic diseases share some characteristic inflammatory features. In fact, atopic children show an increased likelihood of developing IBS as adults. Given these findings, a subset of IBS may be suffering from allergy-related gut diseases. In this review, we present the allergy-related comorbidities of IBS, including genetic, environmental, and immunologic factors. We discuss studies demonstrating an increased sensitization of IBS patients to aeroallergens compared to food allergens. We then postulate potential pathophysiological mechanisms underlying both IBS and aeroallergens in the gut, followed by potential implications in the screening and treatment of allergies in IBS patients.

Protective Effect of Breastfeeding on the Adverse Health Effects Induced by Air Pollution: Current Evidence and Possible Mechanisms

Air pollution is a major social, economic, and health problem around the world. Children are particularly susceptible to the negative effects of air pollution due to their immaturity and excessive growth and development. The aims of this narrative review were to: (1) summarize evidence about the protective effects of breastfeeding on the adverse health effects of air pollution exposure, (2) define and describe the potential mechanisms underlying the protective effects of breastfeeding, and (3) examine the potential effects of air pollution on breastmilk composition and lactation. A literature search was conducted using electronic databases. Existing evidence suggests that breastfeeding has a protective effect on adverse outcomes of indoor and outdoor air pollution exposure in respiratory (infections, lung function, asthma symptoms) and immune (allergic, nervous and cardiovascular) systems, as well as under-five mortality in both developing and developed countries. However, some studies reported no protective effect of breastfeeding or even negative effects of breastfeeding for under-five mortality. Several possible mechanisms of the breastfeeding protective effect were proposed, including the beneficial influence of breastfeeding on immune, respiratory, and nervous systems, which are related to the immunomodulatory, anti-inflammatory, anti-oxidant, and neuroprotective properties of breastmilk. Breastmilk components responsible for its protective effect against air pollutants exposure may be long chain polyunsaturated fatty acids (LC PUFA), antioxidant vitamins, carotenoids, flavonoids, immunoglobins, and cytokines, some of which have concentrations that are diet-dependent. However, maternal exposure to air pollution is related to increased breastmilk concentrations of pollutants (e.g., Polycyclic aromatic hydrocarbons (PAHs) or heavy metals in particulate matter (PM)). Nonetheless, environmental studies have confirmed that breastmilk's protective effects outweigh its potential health risk to the infant. Mothers should be encouraged and supported to breastfeed their infants due to its unique health benefits, as well as its limited ecological footprint, which is associated with decreased waste production and the emission of pollutants.