Edinburgh has some of the highest known rates of inflammatory bowel disease in the world and the figure is expected to rise in the next 10 years.
Researchers say that one in 125 people in the city have Crohn's disease or ulcerative colitis - collectively known as inflammatory bowel disease (IBD).
They predict this figure will rise to 1 in 98 by 2028, putting further strain on NHS resources.
The University of Edinburgh study shows that Crohn's disease affects 284 people out of every 100,000 in Scotland's capital. The world's highest rate is 322 people out of 100,000 in Hesse, Germany.
Ulcerative colitis, meanwhile, affects 432 people out of every 100,000 in Edinburgh - second in the world only to south-east Norway, where it affects 505 people in every 100,000.
These findings broadly apply to the rest of Scotland, the UK and across the western world, researchers say.
Crohn's disease and ulcerative colitis are lifelong and debilitating conditions with no known cure. They are characterised by highly unpredictable and intrusive symptoms, such as diarrhoea, pain, weight loss and extreme fatigue.
The cause is unknown, but it is thought to be caused by an overactive gut immune response in genetically pre-disposed people. The makeup of normal gut bacteria and diet can also play an important role.
While patients with IBD require regular treatment and monitoring, the condition has a low mortality. Experts say this - combined with an ageing population - means the number of older people with IBD is set to increase in the coming years.
The study was published in the scientific journal Gut.
Dr Gareth-Rhys Jones, clinical lecturer in IBD at the University of Edinburgh's Centre for Inflammation Research, said: "IBD is a condition that disrupts the lives of patients and their families all too frequently. Our findings highlight that more resources are needed to provide patients with the research, treatment and care they deserve."
Dr Charlie Lees, a consultant gastroenterologist in the Edinburgh IBD Unit, added: "There is no doubt that IBD is now becoming a global pandemic. This study provides much-needed data and can act as a launchpad for pivotal new studies to help patients."
Sarah Sleet, CEO of Crohn's and Colitis UK, said: "This important study contributes to the growing evidence that the prevalence of IBD is significantly higher than is currently recognised."