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Working night shifts may increase the risk of irritable bowel syndrome
Oct
New evidence from more than 266,000 British adults shows that working permanent night shifts can disrupt the body’s internal clock, alter gut function and increase the risk of irritable bowel syndrome. This discovery could change the way we think about shift work and digestive health.
Test: Night shift work increases the risk of developing irritable bowel syndrome: a prospective cohort study in the UK Biobank. Photo credit: ultramansk/Shutterstock.com
A new study published in Frontiers in Public Health found that working a permanent night shift may increase the risk of irritable bowel syndrome.
Background
Irritable bowel syndrome is a gastrointestinal disorder characterized by: stomachacheabdominal bloating and irregular bowel movements such as constipation and diarrhea. The global prevalence of this disorder ranges from 0.2 to 7.6%, depending on geographic region and population characteristics.
The chronic burden of symptoms associated with irritable bowel syndrome can significantly impair a person’s quality of life and impact daily activity and productivity in the workplace. Although the pathophysiology of this condition is not fully known, existing evidence suggests that visceral hypersensitivity, gut microbiota dysbiosis, impaired gut-brain axis, gut barrier dysfunction, inflammationor neuroendocrine abnormalities could potentially trigger the development of irritable bowel syndrome.
The circadian system is the body’s internal clock that regulates 24-hour physical, mental, and behavioral changes in response to day and night cycles in the environment. This complex phenomenon significantly affects various physiological processes, including metabolism, hormone secretion and immune response.
People working nights or shifts often experience metabolic disorders due to mismatches in circadian rhythm and work schedule. Existing evidence shows that shift work can make a significant difference increase the risk of diabetesobesity, metabolic syndrome, hypertension and cardiovascular diseases.
Given the potential link between shift work and metabolic disorders, researchers from Jiaotong University in China conducted a large-scale prospective cohort study to investigate the association between shift work and the risk of irritable bowel syndrome among shift workers living in the UK.
Study design
The researchers analyzed data from 266,605 participants in the UK Biobank, a large-scale database of over 500,000 participants from England, Scotland and Wales. Specifically, they analyzed data on shift work patterns, the prevalence of irritable bowel syndrome and potential confounding factors, including sleep patterns, mental health, body mass index (a measure of overweight or obesity), and smoking and alcohol drinking habits.
To avoid reverse causality, participants who were previously diagnosed with irritable bowel syndrome, celiac disease, or gluten sensitivity were excluded.
Key findings
Analysis of the study found 5,218 new cases of irritable bowel syndrome in the database over the nine-year follow-up period.
The analysis, taking into account participants’ age and gender as well as potential confounding factors, found that participants who always work night shifts had a higher risk of developing irritable bowel syndrome than those who never or rarely worked night shifts. The observed increase in disease risk was more pronounced among participants whose body mass index exceeded 25 kilograms per square meter.
The risk of developing irritable bowel syndrome showed no significant differences between participants who sometimes or usually work night shifts and those who never or rarely work night shifts. Specifically, the fully adjusted hazard ratio for people who always worked the night shift was 1.36, indicating a moderate but statistically significant increase in risk.
Importance of the study
The study shows that working a permanent night shift may increase the risk of irritable bowel syndrome, especially in workers whose body mass index is above 25, which is considered overweight or obese. The risk of disease remains high among workers who always work night shifts, regardless of their age, gender, sleep duration and mental health status.
Researchers have suggested some mechanisms that may explain the observed association between night shift work and the risk of irritable bowel syndrome. One of the possible mechanisms is disruption of the circadian rhythm as a result of an altered sleep-wake cycle, which in turn may induce dysbiosis of the intestinal microflora, impair gastrointestinal motility, increase the secretion of pro-inflammatory mediators and promote low-grade intestinal inflammation. All these changes may potentially contribute to the pathogenesis of irritable bowel syndrome.
Night shift work is known to inhibit the secretion of melatonin, a hormone necessary to regulate sleep and protect the digestive tract. Although melatonin supplementation was not tested in this study, the authors note that previous research has shown that it may help reduce symptoms and improve quality of life in patients with irritable bowel syndrome.
Shift workers’ eating habits and irregular eating patterns may also be potential risk factors for irritable bowel syndrome.
Of note, the current study found that the effect of night shift work on disease risk is more pronounced among participants who are overweight or obese. This additional risk may be due to obesity-related changes in intestinal transit time, excessive consumption of ultra-processed foods, altered gut microbiota composition, and low-grade systemic inflammation. Lower levels of physical activity among obese or overweight people may also be a contributing factor.
Due to the observational design, the study was unable to establish causality of the observed associations. In addition, the study analyzed data from UK Biobank participants, mainly of European origin. This limitation may limit the generalizability of the results to other populations. Additional limitations include the use of self-reported sleep duration data and the inability to distinguish IBS subtypes.
Overall, this large-scale population-based study with long-term follow-up suggests that people diagnosed with irritable bowel syndrome or those at increased risk of developing the condition may benefit from avoiding night shifts and maintaining a regular circadian rhythm.
However, further longitudinal and interventional studies are needed to confirm the causal relationship and explore the underlying mechanisms.
