Scientists haven’t identified all the many causes of Crohn’s disease, but they’ve found certain groups of people who seem to be at higher risk.
Over 3 million people in the U.S. have Crohn’s disease. The condition can affect any part of the digestive tract – the organs that break down and process your food, from the mouth to the anus. It includes symptoms such as diarrhea, abdominal pain, and weight loss. Crohn’s disease is one of two inflammatory bowel diseases (IBDs), the other being ulcerative colitis (UC), which tends to affect the large intestine or colon.
Here’s what we know about who gets Crohn’s disease.
You’re most likely to be diagnosed in your teens and 20s. About one-sixth of people show symptoms before the age of 15.
Some studies have suggested that there is a second surge in Crohn’s onset and diagnosis when you reach 60 or so, but this is controversial.
“Some of this may be detection in the sense that people at that age have colonoscopy, CT scan, and MRIs done,” says James Lewis, MD, professor of medicine and epidemiology, Perelman School of Medicine at the University of Pennsylvania.
No one knows exactly why the majority of Crohn’s cases turn up so early in life, but it could be due to a combination of environmental exposures, such as dietary changes that trigger susceptible, or easily influenced, genes, Lewis says.
Where You Live
The U.S. and Canada, United Kingdom, Northern and Western Europe as well as Australia and New Zealand, have the highest rates of Crohn’s disease.
That said, more and more people in Asia, South America, and Africa are now also developing the condition. Immigrants moving from developing regions to the more industrialized world have higher rates of Crohn’s disease than their peers who don’t relocate.
The high rates of Crohn’s in industrialized areas may be related to lifestyle factors including diet, lack of sunlight leading to vitamin D deficiency, and environmental toxins from pollution.
Crohn’s disease also seems to be concentrated in urban areas. “It’s hard to know whether it’s access to care and testing versus actual prevalence of disease,” Lewis says.
Slightly more women than men are diagnosed with Crohn’s in the industrialized world, while the opposite is true in the developing world.
“We don’t think of it as a disease of women versus men,” says Lewis, who is also chief scientist for the IBD Plexus Research Program at the Crohn’s & Colitis Foundation.
Crohn’s disease is more common in white people than African American or Hispanic people, although it can affect all racial and ethnic groups.
Again, chances are that this is related to lifestyle and environmental issues rather than genetics.
The exception may be Ashkenazi Jews, who have a higher rate of Crohn’s disease. “This may be more of a genetic increased risk,” Lewis says.
Your Use of Drugs
Nonsteroidal anti-inflammatory drug (NSAIDs) and antibiotic use over long periods of time may also increase the risk of developing Crohn’s disease, although this is far from certain. Oral contraceptives -- birth control -- and hormone replacement therapy have been linked with the development of IBD but, again, this is not yet confirmed.
NSAIDs like aspirin can cause intestinal ulcers which look like Crohn’s disease. They can also result in symptoms that mimic Crohn’s.
Both NSAIDs and antibiotics do seem to contribute to flares. “We recommend sticking with acetaminophen (Tylenol),” Lewis says.
You’ve Had Previous Gastrointestinal Infections
Having an intestinal infection that causes diarrhea is associated with a later risk of developing IBD.
One large study published in 2009 observed that people who had had a confirmed Salmonella or Campylobacter infection were almost three times as likely to develop IBD over a 15-year period compared with people who had never had one of these infections. The risk was doubled in the first year post-infection. Salmonella and Camplyobacter are both bacterial infections that can be spread by contaminated food.
“We don’t know if it’s casual, but you can hypothesize that one’s intestinal microbiome never fully recovered and set them up for that; or you already were predisposed,” Lewis says. In other words, the infections may kick off an immune response that alters the composition of gut organisms.
If You Smoke
Smoking is the most clear-cut environmental risk factor for developing Crohn’s disease, Lewis says. If you’re a current or former smoker, you may have as much as double the risk of developing Crohn’s compared with people who have never smoked. Smoking is also related to having more flares and needing more intensive treatment.
Again, researchers have not teased out the exact reasons for the connection but it may have to do with stress caused by toxic chemicals, production of more gastric acid in the stomach, and reduced blood flow to the intestine.
Eating Processed Foods
Although less studied than smoking, diet may also be a culprit in developing Crohn’s disease. “The overall research suggests that greater consumption of a ‘healthy diet,’ such as fruits and vegetables and less consumption of red and processed meat seems to be associated with a lower risk of Crohn’s disease,” Lewis says.
Ultraprocessed foods, like breakfast cereal, may be a particular villain while fiber can cut the risk.
This may explain why industrialized nations top the list of Crohn’s incidence, given that highly processed diets are more plentiful in Western regions.
Having a Family History of Crohn’s
Research has shown that if you have a parent, sibling, or child who has Crohn’s disease, you’re more likely to develop the condition as well. Still, this accounts for no more than about 25% of patients with IBD.
So far, researchers have pinpointed about 200 genes that contribute to a small portion of all Crohn’s disease cases. Environmental triggers seem to play an outsize role.
“Genetics at most account for 50% of the risk, so we know that this is a combination of being genetically predisposed and having appropriate exposures in the environment,” Lewis says.
Having an Appendectomy
Although earlier research had linked appendectomies with development of Crohn’s disease, there’s no wide agreement that this is actually the case. It’s possible that Crohn’s came first, with Crohn’s symptoms contributing to the need for an appendectomy, Lewis says. Or symptoms of Crohn’s were mistaken for appendicitis.