Sunday, December 9, 2012

IBD By The Numbers, Part 2


Crohns and Ulcerative Colitis, by the Numbers

There are several areas of statistical interest in Crohns.  In another look at the numbers, I've highlighted areas where questions arise on three brief topics below - the diseases that are co-morbid with IBD, the age of diagnosis, and the number of bowel movements a day. I'll be throwing in a few cornucopia posts like this every few weeks to address a few simpler questions, intersperced with more in-depth posts.

Co-morbid Diseases with IBD


I previously noted the association between IBD and depression.  What about other diseases that are frequently co-morbid with IBD?  The specific diseases are different between UC and Crohns.  As expected, UC has more involvement with diseases of the large intestine like Hirschprung’s disease, whereas Crohns has impacts on bone-related diseases like osteoporosis (due partly to malabsorption).  Both have impacts on kidney and liver functions.  Interestingly, there is a higher likelihood of schizophrenia with UC.  All forms of IBD have higher comorbidity with other autoimmune disorders, such as psoriasis and rheumatoid arthritis.
The table below shows the proportional morbidity ratio (PMR) for the various diseases.  The PMR is equal to the number of individuals with the disease who have the condition divided by the number of people from the general population in the same sample size who have the condition.  A PMR of 1 would mean there is no higher likelihood than an average person.  Higher PMRs mean a much higher correlation between having IBD and the disease in particular. (1,2)

Condition
Crohns
Ulcerative Colitis
Osteoporosis
3.2
X
Ankylosing spondylitis
33.2
X
Cirrhosis of liver without mention of alcohol
1.7
X
Sequela of chronic liver disease
1.6
X
Cholangitis
5.9
16
Amyloidosis
6.6
X
Acute renal failure unspecified
2.3
3.1
Acute renal failure with lesion of tubular necrosis
X
9.9
Uremia NOS
2
X
Calculus of kidney
8.5
X
DIC, afibrinogenemia, fibrinolysis pathologies
4.7
4.6
Coagulation defect other unspecified
3.8
X
Pulmonary embolism
2.3
2.2
Hirschsprung’s disease
X
246.1
Schizophrenia
X
4.6
Asthma
1.43
1.66
Bronchitis
1.86
2.1
Arthritis
1.24
1.44
Multiple Sclerosis
X
1.9
Psoriasis
1.59
1.65
Pericarditis
3.07
3.33

Age of Onset


When do we get diagnosed with IBD?  Crohn’s disease tends to be an earlier diagnosis than Ulcerative Colitis, but only by 2 or 3 years.  Generally, the average age of diagnosis is 26, with a standard deviation of 12 years, (14-38 year of age being the expected age of diagnosis).  This doesn’t necessarily correlate to the onset of the disease itself – individuals can be misdiagnosed with irritable bowel syndrome (IBS), gastroenteritis, or other conditions for years before finalizing the diagnosis.  Nor does the distribution guarantee that it will occur during this period – it has been diagnosed in infants and retirees.  (3)

Number of Bowel Movements


What about normal bowel habits?  Most of us count the number of times we need to go every day as a measure of health.  The exact number of times we should be expecting to use the bathroom is based on diet, genetics, medications and a host of other factors not necessarily related to the underlying IBD (try eating $10 worth of Taco Bell, with or without IBD, and see what that does…)  Once a day is the median number of times to go, but there is actually a range of what is “normal”.  95% of the population (bowel-typical?) goes between three times a week and three times a day. (4)

Bottom Line

  •  IBD is generally diagnosed between the ages of 14 and 35.
  • The average person uses the bathroom between 3 times a week and 3 times a day, with 1 time a day being the median.
  • Crohns and IBD are both comorbid with other diseases, including autoimmune diseases and those effecting the liver and kidneys. 


(1)    Claudia Cucino, M.D., Amnon Sonnenberg, M.D., (M.Sc.).  The comorbid occurrence of other diagnoses in patients with ulcerative colitis and Crohn’s disease.  American Journal of Gastroenterology, 2001.
(2)    Charles N. Bernstein, Andre Wajda,  and James F. Blanchard.  The Clustering of Other Chronic Inflammatory Diseases in Inflammatory Bowel Disease: A Population-Based Study.  Gastroenterology, 2005.
(3)    JM Polito 2nd, B Childs, ED Mellits, AZ Tokayer, ML Harris, TM Bayless.  Crohn's disease: Influence of age at diagnosis on site and clinical type of disease.  Gastroenterology, 1996.
(4)    S. Walter, O. Hallböök, R. Gotthard, M. Bergmark and R. A Population-based Study on Bowel Habits in a Swedish Community: Prevalence of Faecal Incontinence and Constipation.  Scandinavian Journal of Gastroenterology, 2002.   

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