Using a UK database of electronic medical records, he and his colleagues identified 367 children and adults diagnosed with Crohn's disease and 591 diagnosed with ulcerative colitis between 2005 and 2008. The researchers matched each of those people to five IBD-free individuals the same age and sex.
They then used air-quality data from government monitors to assess the average yearly levels of three air pollutants in the study subjects' residential areas.
The pollutants included nitrogen dioxide, which is produced largely by vehicles and is highest in urban, high-traffic areas; sulfur dioxide, which is produced through industrial processes, including the burning of coal and oil; and particulate matter, fine particles emitted via car exhaust, as well as power plants and other industrial sources.
Overall, Kaplan's team found no association between IBD and the three air pollutants across the study group as a whole.
However, young people — those age 23 or younger — were about twice as likely to be diagnosed with Crohn's disease if they lived in a region in the top 60 percent of nitrogen dioxide levels, versus the bottom 20 percent.
Similarly, people age 25 or younger were twice as likely to have ulcerative colitis if they lived in areas with higher sulfur dioxide levels. However, there was no evidence of a “dose-response” relationship — that is, the risk of ulcerative colitis climbing steadily as sulfur dioxide levels rose.
That lack of a dose-response, Kaplan told Reuters Health, “makes us a little more cautious about that finding.”
Indeed, he urged caution in interpreting the findings as a whole. While he and his colleagues tried to account for other factors — such as study subjects' smoking habits and socioeconomic status — they cannot rule out the possibility that something other than air pollution itself accounts for their findings.
“This is an interesting association,” Kaplan said. But, he added, the findings do not prove cause-and-effect.
As for why air pollution would affect IBD risk, Kaplan said he could only speculate, based on research into other health conditions, including heart and lung disease. Studies indicate that air pollutants can trigger inflammation in the body; that, Kaplan explained, raises the possibility that in genetically predisposed people, air pollution may trigger an inflammatory response in the intestines that leads to IBD.
Since the current study found a relationship between pollutants and IBD only in young people, the findings also raise the question of whether children and teenagers are particularly susceptible to any effects of air pollution on the risk of the digestive disorders.
Much more research is needed, Kaplan said — both larger population studies and research in animals to see how exposure to various air pollutants might affect intestinal health.
He added that no one is proposing that air pollution is the environmental cause of IBD; if it does turn out to be a factor, he said, it will likely be one of many players.
But if air pollution is confirmed as a risk factor, there would be important implications, Kaplan said, since air quality is something that can be modified.
The team set out to examine levels of depression and anxiety between adults with celiac disease following a gluten-free diet and in control subjects drawn from the general population.
For their study, the team used the Hospital Anxiety and Depression Scale to measure levels of anxiety, depression, and likely anxiety or depressive disorder, in 441 adult patients with celiac disease recruited by the German Celiac Society. They then conducted the same assessments on 235 comparable patients with inflammatory bowel disease (IBD), either in remission or with slight disease activity. They did the same for the cross-sample control group of 441 adults from the general population.
The team used regression analysis to test possible demographic and disease-related predictors of anxiety and depression in celiac disease. Demographic predictors included age, sex, social class, and family status. Disease-related predictors included Latency to diagnosis, duration of GFD, compliance with GFD, thyroid disease.
The team found that female gender (P = 0.01) was the main predictor (R(2) = 0.07) of anxiety levels in patients with celiac disease. Female patients had a higher risk for a probable anxiety disorder (OR = 3.6, 95% CI: 1.3-9.4, P = 0.01) Patients who lived alone (OR = 0.5, 95% CI: 0.2-0.9, P = 0.05) enjoyed a lower risk of anxiety disorder. None of the demographic and medical variables for which the team screened predicted either depression levels or risk for a probable depressive disorders.
Patients with celiac disease showed anxiety levels of 6.6 +/- 3.4, and those with IBD, anxiety levels of 6.9 +/- 3.7, both higher than the general population's level of 4.6 +/- 3.3 – (both P < 0.001). Depression levels were similar for people with celiac disease (4.2 +/- 3.4), IBD (4.6 +/- 3.4) and the general population (4.2 +/- 3.8) (P = 0.3). Rates of likely anxiety disorders in people with celiac disease were 16.8%, and 14.0% for IBD, both higher than the rates of 5.7% in the general population (P < 0.001). All three groups showed similar rates of probable depressive disorder (P = 0.1).
Their results provide strong indications that adult women with celiac disease on a gluten-free diet suffer higher rates of anxiety than persons of the general population. They encourage clinicians to provide anxiety screens for adult women with celiac disease on a gluten-free diet.
For the first time, in a large prospective study, researchers have identified an association between high protein intake and a significantly increased risk of inflammatory bowel disease (IBD). While doctors have long suspected that diet contributes to IBD, little has been assessed, and the studies conducted have been retrospective, which are less informative because they rely on the study participants' ability to recall what they have consumed in the past. This study examined the effects of different sources and amounts of protein.
Using participants in France's E3N cohort study, researchers led by Prevost Jantchou, MD, of the Center for Research in Epidemiology and Population and colleagues identified 77 women ages 40 to 65 with validated cases of IBD. In each case, the onset of IBD occurred after the first dietary questionnaire was administered, thereby assuring that they could be studied prospectively.
Dr. Jantchou examined participants' macronutrient (protein, fat and carbohydrate) intake, and determined that more than two-thirds of them had elevated levels of protein intake. Participants were divided into three groups based on their mean protein intake: the lowest intake group had a mean daily protein intake of 1.08 grams/kg of body weight; the middle group had 1.52 grams/kg; and the highest group had 2.07 grams/kg. The FDA recommends a daily intake of 0.8 grams of protein per kilogram of body weight.
When examining the effects of specific types of protein, Jantchou found that animal protein represented a threefold risk of developing IBD in the highest group compared to the lowest group. Specifically, animal protein from meat and fish, not dairy, created an increased risk, while vegetable protein created no increased risk of developing IBD.
Researchers found that the increased risk from animal protein intake were the same for Crohn's disease and ulcerative colitis. They also found that smoking and hormonal therapy, two factors known to be related to the risk of IBD, did not change their results.
“Our findings represent a tremendous step forward in our understanding of inflammatory bowel disease,” said Dr. Jantchou. “For years we've known there was a connection between diet and IBD, and we now know specifically which aspect of diet is related to disease occurrence. The next step is to look at the effect of animal protein in patients already diagnosed with IBD to be able to give them better dietary advice.”