Risk factors for Crohn's disease

Crohn’s disease is most common in Western Europe and North America, where it affects 100 to 150 in every 100,000 people. Small studies show that it’s relatively uncommon in Africa. However, it’s speculated that, as urbanisation becomes more popular, the incidence will rise.

It isn’t known how many people suffer from Crohn’s disease in South Africa.

Characteristics:

• Crohn’s disease appears to be slightly more common in women than in men.
  
• There is a trend for the frequency to increase with greater distance from the equator. 
  
• The disease is much less common in Asia, Africa and South America. 
  
• Worldwide, those of Eastern European (Ashkenazi) Jewish origin have a five-fold higher risk of being diagnosed with Crohn’s disease.  
  
• Crohn's disease can occur at any age. However, most people develop the condition when they’re young (before 30 years of age).
  
• Crohn’s disease may be hereditary. If you have a close relative (parent, sibling or child) who suffers from the disease, you’re more likely to develop it. As many as 1 in 5 people with Crohn's disease have a family member with the disease.
  
• Research shows that if you live in an urbanised area or industrialised country, you may have a greater risk of developing Crohn's disease. 
  
• People living in northern climates seem to be at greater risk.
  
• In South Africa, researched showed that Cape Coloured people were significantly more likely to develop complicated Crohn’s disease over time when compared to Caucasians. 
  
• Flare-ups are more likely to occur in spring and summer.

Non-modifiable risk factor: genetics 
Research has shown that coeliac disease and Crohn's disease share several genetic risk factors, as people with coeliac disease have an increased risk of developing Crohn's disease. A study has pinpointed two new, shared genetic risk loci – that is, specific locations of genes or DNA sequence on a chromosome.

Researchers have also found two shared risk loci that had previously been independently identified for each disease. In other words, there seems to be an inherited component to Crohn's disease risk. 

Modifiable risk factor: cigarette smoking
If you’ve been diagnosed with Crohn’s disease, you’ll be advised to quit smoking immediately if you do. Smoking is a strong risk factor for developing Crohn's disease and speeds up its progression.

Research also shows that people with Crohn’s disease who smoke are more likely to require surgery. 

Reviewed by Kim Hofmann, registered dietitian, BSc Medical (Honours) Nutrition and Dietetics, BSc (Honours) Psychology. December 2017.