STOCKHOLM — Certain occupations, particularly skilled trades involving pollutant exposure and physically demanding work, were associated with a higher risk of inflammatory bowel disease (IBD), according to findings from a large cross-population study spanning the United Kingdom and China. 

“Our results show that it’s not just the job title that matters, but what people are exposed to at work, how they work, and the broader social context of that work,” said Jie Chen , PhD, of the Third Xiangya Hospital, Central South University, Changsha, China, who presented the study during the opening plenary here at the European Crohn’s and Colitis Organisation Congress (ECCO) 2026. 

“These factors appear to interact to shape IBD risk across very different populations,” Chen said, adding that occupational health is often an overlooked target. 

“Improving air quality in the workplace and focusing on heavy labor occupations could be good strategies for IBD prevention,” he told the audience. 

“While adverse occupational exposures increase IBD risk, protective measures, a healthy lifestyle, balanced mental health, and enhanced social welfare reduce it,” he added. 

Filling a Knowledge Gap in IBD Risk 

The global burden of IBD has risen sharply alongside industrialization and changes in work patterns, yet the role of occupation — a key link between environmental exposures and daily life — has remained poorly understood.

Previous studies have suggested associations between certain jobs and IBD risk — for example, higher IBD disability rates in white-collar workers — but most have focused on broad occupational categories and single populations, limiting insight into underlying mechanisms.

“What has been missing is a systematic way to disentangle whether risk comes from the job itself or from sp ecific exposures and behaviors embedded within that job,” Chen explained.

To address this, the researchers designed a two-step, multicohort study combining occupational epidemiology with detailed exposure analysis to systematically understand more about the relationships between occupations and IBD risk and elucidate the factors through which occupations influence individual susceptibility to IBD.

In the first phase, the team assessed IBD risk across 353 occupations coded using the UK Standard Occupational Classification system among 120,290 participants in the UK Biobank, including 9748 individuals diagnosed with IBD. Occupations comprised single jobs held for 10 years or more. 

The researchers then validated key findings in an independent Chinese cohort derived from the Hu n an medical insurance database , covering nearly 21 million people , one of the largest population-based datasets used for occupational IBD research to date.

Pollutants, Work Patterns, and Social Status 

To clarify the mechanisms within occupations, the researchers used hazard models to evaluate associations between IBD risk and occupation-related factors, including pollutants (airborne, dust-related, and complex chemical contaminants), occupation-specific behaviors (work-related physical activity, sedentary time, work stress, and night shifts), and occupation-related socioeconomic status. 

Subgroup analyses identified 16 occupations associated with Crohn’s disease and six linked to ulcerative colitis , with notable signals among drivers, certain manual laborers, and some technical roles.

“Strikingly, the excess IBD risk associated with skilled trades occupations , typically blue-collared jobs, was observed in both cohorts, despite differences in healthcare systems, culture, and baseline disease prevalence,” Chen remarked, strengthening confidence that real biological and environmental effects were being observed.

He added that bus and coach drivers, community workers, and electricians had higher ulcerative colitis risk, while medical and dental technicians, accountants, and therapists had higher Crohn’s disease risk.

Diesel exhaust stood out in the analysis of pollutants and IBD risk. High exposure to diesel exhaust was associated with a 56% increased risk of IBD overall (hazard ratio [HR], 1.56; 95% CI, 1.14-2.13), and a 43% higher risk of Crohn’s disease in particular (HR, 1.43; no confidence interval given), said Chen. “This explains why drivers and machine operatives are at higher risk.” 

Exposure to mists and aerosols also increased the risk of IBD by 31% (HR, 1.31; 95% CI, 1.04-1.66), supporting growing evidence that airborne pollutants may act as environmental triggers in IBD pathogenesis, he added. 

Work behaviors also mattered. High levels of occupational physical activity were associated with an 18% higher IBD risk (HR, 1.18; 95% CI, 1.05-1.32), a counterintuitive finding that contrasts with the protective effects often seen for leisure-time exercise. “It challenges the belief that all exercise is good, with heavy labor being different to leisure exercise,” Chen pointed out. 

In contrast, higher occupational socioeconomic status was protective , reducing IBD risk by 27% (HR, 0.73; 95% CI, 0.66-0.90). The protective effect was strongest among individuals with both higher income and higher occupational status, underscoring the role of social determinants of health.

More Studies Needed to Clarify Causal Pathways 

The study expands the environmental framework of IBD by integrating occupation-related exposures with behavioral and social factors, Chen noted. However, he cautioned that the study is observational and cannot establish causality. 

Diet, lifestyle, and other unmeasured factors may also contribute, and further mechanistic research is needed, he said.

Commenting for Medscape Medical News, James Lindsay, MD, PhD, gastroenterologist at Barts Health NHS Trust, London, who was not involved in the study, said the cross-population design was a major strength.

“Using two very different healthcare and occupational systems to validate risk signals is impressive,” Lindsay said. “The challenge now is to understand how these exposures translate into gut inflammation and whether modifying them could realistically reduce risk.”

He added that future studies integrating dietary patterns, genetics, and occupational exposures at the individual level could further clarify causal pathways.

The study authors reported no relevant conflicts of interest. Lindsay declares no relevant financial disclosures.