A groundbreaking international study, with involvement from the University of Otago, Christchurch, has identified four distinct stages associated with the global growth of Inflammatory Bowel Disease (IBD), with a prediction that case numbers will explode by 2045 – including here in Aotearoa New Zealand.
The epidemiological study, published in the prestigious British medical journal Nature, is the largest ever undertaken on IBD, involving 50 researchers worldwide. The collaborative analysed a century worth of historical data from more than 500 studies across 80 regions, New Zealand included.
Professor Richard Gearry
Study co-author, Professor Richard Gearry from the University of Otago, Christchurch's Department of Medicine, says the landmark study charts the global growth of IBD across time and geography, pinpointing its evolution.
"This important study has, for the first time, identified four distinct stages of IBD development across the globe, providing a framework which, its hoped, will allow health systems such as ours to better anticipate and manage the growing burden of IBD in the community," Professor Gearry says.
He says studies undertaken in Canterbury in the year's 2006, 2014 and 2024 were included in the paper.
"As a gastroenterologist seeing more and more patients with IBD in clinic, we've been surprised to discover that IBD diagnoses in Canterbury have almost tripled from 1420 people in 2006 to more than 4000 last year," Professor Gearry says.
University of Otago, Christchurch, Department of Medicine PhD student Angela Forbes was another co-author on the landmark paper. She has just submitted her thesis, which includes data from the study.
Angela Forbes
"Currently one in 150 people in Canterbury are living with IBD, with complex modelling undertaken by our Canadian collaborators now showing the proportion of Cantabrians living with IBD is likely to exceed 1 per cent of the New Zealand population within a decade," Ms Forbes says.
IBD, comprising Crohn's disease and ulcerative colitis, causes chronic ulceration and inflammation in the gut. Its peak onset is between 20 and 40 years of age, with a range of lifelong symptoms such as rectal bleeding, abdominal pain, mucus in stool, diarrhoea, weight loss, fever and inflammation of other organs including the eyes, skin and joints. Treatment for IBD usually involves drug therapy, or in some severe cases, surgery.
The study analysed both the incidence and prevalence of IBD cases, newly demonstrating that IBD progresses through four distinct, predictable stages.
Stage one is called Emergence, currently experienced in the lowest-income countries across Africa, Asia, and Latin America, where both incidence and prevalence are sporadic.
More economically wealthy regions within Africa, East Asia, the Middle East and Latin America are classified as being in stage two, Acceleration in Incidence. This stage is marked by a rapid increase in new diagnoses, although overall prevalence remains low. Raising awareness of IBD, improving diagnosis, and ensuring access to trained healthcare providers and diagnostic tools such as colonoscopy are seen as vital in this stage.
Heavily industrialised countries such as New Zealand, other parts of Oceania, North America and Europe, are categorised as being in stage three, called Compounding Prevalence. This stage sees growing numbers of people living with IBD, including an increasing proportion of seniors. Incidence stabilises, yet the number of people living with IBD steadily increases, due to the fact IBD is typically diagnosed in young adults and is associated with low mortality, allowing the affected population to accumulate over time.
"To keep up with rising demand, our health system needs to plan ahead and invest more in care designed to specifically meet the needs of people with IBD. We also need to focus on more prevention, research and earlier intervention."
– Professor Richard Gearry
Stage four is called Prevalence Equilibrium, when the ageing IBD population and age-related mortality begin to balance out the number of new diagnoses. As a result, IBD growth slows and can eventually plateau.
"Regions such as ours face a dual challenge, managing new cases in young adults while also supporting older IBD patients with more complex health needs such as heart disease and diabetes," Professor Gearry says.
"To keep up with rising demand, our health system needs to plan ahead and invest more in care designed to specifically meet the needs of people with IBD. We also need to focus on more prevention, research and earlier intervention."
Professor Gearry says New Zealand, like many industrialised countries, faces a huge rise in IBD case numbers by 2045.
"Currently around 20,000 people in New Zealand are living with IBD, with incidence particularly rising among the Māori population. Case numbers are expected to exceed 40,000 by 2045.
"Many patients experience years of diagnostic delay, resulting in worse outcomes, which is why more resourcing and investment is sorely needed" Professor Gearry says.
