Background: There is increasing experimental evidence that hypoxia induces inflammation
in the gastrointestinal tract. Hypoxia-inducible transcription factor (HIF)-1α influences
adaptive immunity and has been shown to induce barrier-protective genes in the case of
experimentally-induced colitis. The clinical impact of hypoxia in patients with inflammatory
bowel disease (IBD) is so far poorly investigated. Aim: We wanted to evaluate if flights and
journeys to regions ≥2000 meter above sea level are associated with the occurrence of flares
in IBD patients in the following 4 weeks. Methods: A questionnaire was completed by
inpatients and outpatients of the IBD clinics of three tertiary referral centers presenting with
an IBD flare in the period from Sept 1st 2009 to August 31st 2010. Patients were inquired
about their habits in the 4 weeks prior to the flare. Patients with flares were matched with
an IBD group in remission during the observation period (according to age, gender, smoking
habits, and medication). Results: A total of 103 IBD patients were included (43 Crohn's
disease (CD), whereof 65% female, 60 ulcerative colitis, whereof 47% female, mean age
39.3±14.6 years for CD and 43.1±14.2 years for UC). Fifty-two patients with flares were
matched to 51 patients without flare. Overall, IBD-patients with flares had significantly more
frequently a flight and/or journey to regions ≥ 2000 meters above sea level in the observation
period compared to the patients in remission (21/52 (40.4%) vs. 8/51 (15.7%), p=0.005).
There was a statistically significant correlation between the occurrence of a flare and a flight
and/or journey to regions ≥ 2000 meters above sea level among CD patients with flares as
compared to CD patients in remission (8/21 (38.1%) vs. 2/22 (9.1%), p=0.024). A trend
for more frequent flights and high-altitude journeys was observed in UC patients with flares
(13/31 (41.9%) vs. 6/29 (20.7%), p=0.077). Mean flight duration was 5.8±4.3 hours. The
groups were controlled for the following factors (always flare group cited first): age (39.6±13.4
vs. 43.5±14.6, p=0.102), smoking (16/52 vs. 10/51, p=0.120), regular sports activities (32/
52 vs. 33/51, p=0.739), treatment with antibiotics in the 4 weeks before flare (8/52 vs. 7/
51, p=0.811), NSAID intake (12/52 vs. 7/51, p=0.221), frequency of chronic obstructive
pulmonary disease (both groups 0) and oxygen therapy (both groups 0). Conclusion: IBD
patients with a flare had significantly more frequent flights and/or high-altitude journeys
within four weeks prior to the IBD flare compared to the group that was in remission. We
conclude that flights and stays in high altitude are a risk factor for IBD flares.