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EPIDEMIOLOGY


are relatively young. There are very low rates of death in younger people, even for those with severe disease. This means that it is necessary to study a very large group of people, and/ or study them for a very long period of time, in order to identify any trends of increased death. Second, it can be difficult to decide if a death was due to the underlying presence of IBD, even for people who die from a gastrointestinal disease.


Crohn’s Disease


There have been at least ten population-based studies of mortality in CD patients. Seven of these studies have found an increased risk of death, while three studies have reported a slightly lower risk of death. When faced with conflicting results from multiple studies, researchers can conduct a meta-analysis. This is a statistical technique which combines data from multiple independent studies to generate a more precise estimate. Studies which are similar in methods and in quality can be combined, with more weight given to studies which include more patients (and less weight given to smaller studies).


A meta-analysis was conducted for the Crohn’s and Colitis Australia, previously known as Australian Crohn’s and Colitis Association (ACCA), in 2006. It combined ten studies and found that CD was associated with a statistically significant 47% increase in the mortality risk (range, 30-67%).45


The results of this meta-analysis were very close to the result of a recently published meta- analysis of thirteen studies, which found 52% increase in the risk of mortality (range, 32%- 74%).46


Since the conduct of these meta-analyses, two other important studies have been


published, from California and Denmark; they reported similar results (a 40% increase in mortality risk in California and 31% in Denmark).47,48


There were increased death rates from cancer, cardiovascular disease, respiratory disease, GI diseases, infections, and complications following medical and surgical interventions.45 Meta-analyses of colorectal and small bowel cancer studies have found that people with CD had an elevated risk of colorectal cancer, estimated at 2.9% over the ten years following diagnosis of CD.49,50


Ulcerative Colitis


Similarly, there have been several studies of ulcerative colitis mortality, with conflicting results. Crohn’s and Colitis Australia conducted another meta-analysis, using these studies: three studies reporting an increased risk, and five studies reporting a decreased risk. However, with UC, there was no significant difference in mortality risk. That is, people with UC experienced the same mortality risk as the general population. These results were duplicated in two studies published since the meta-analysis: the large California study47 study (limited to the first ten years since diagnosis of UC).51


, as well as a large European


It appeared that people with UC had increased deaths from some diseases (gastrointestinal diseases, infections, colon cancer) but these were offset by low rates of other diseases (cardiovascular disease, lung cancer).45


THE IMPACT OF INFLAMMATORY BOWEL DISEASE IN CANADA 42


This could be due to the fact that people with UC are


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