Marked regional variations in the prevalence of inflammatory bowel disease in a limited geographical region are not associated with compounds in the drinking water

Abstract

Objective: The incidence of autoimmune diseases, especially inflammatory bowel disease (IBD), has increased substantially. Globally, there are vast differences varying from 0.2/10⁵ in some Asian countries to over 80/10⁵ in the Faroe Islands. Environmental factors have been suggested as triggers. The aim was to investigate the incidence and prevalence of IBD in the 33 municipalities in the county Scania in Southern Sweden, an area comprising 100 × 100 km with 1,274,069 inhabitants. Furthermore, we wanted to explore whether compounds in the drinking water could contribute to IBD; one report from Norway has suggested that iron in drinking water could contribute to UC.

Methods: Patients with CD and UC were identified through the ICD-10 diagnosis database during the period 2000–2013. Water analyses for pH, alkaline, nitrate, sulphate, iron, magnesium and calcium were based on established methods and compared with the prevalence of IBD using Student’s t-test.

Results: A total number of 8925 patients were identified. The incidence for CD and UC were high (mean 16.4/10⁵, range 13.6–17.9 and 25.3/10⁵, range 21.3–28.0, respectively). The prevalence varied substantially (p < .0001 for both; CD mean 0.30%, range 0.15–0.42 and UC mean 0.42%, range 0.32–0.56). No correlation between IBD and the chemical compounds in the drinking water could be shown.

Conclusions: The incidence rates of both CD and UC were high. The prevalence varied from 200% to 300% between the municipalities, despite the limited geographical area indicating that local conditions are of importance. However, chemical compounds in the water were not associated with this variation.

Keywords:

• Crohn’s disease
• drinking water
• epidemiology
• prevalence
• ulcerative colitis

Acknowledgements

The author thanks the Health navigator for preparing patient data, Anna Åkesson for valuable statistical advice and calculations, Elin Meigård for technical support and all other persons we have been in contact with in the municipalities of Skåne for supporting this study. Furthermore, this investigation would not have been possible without helpful guidance and information about water and analyses provided by Peter Dahlqvist and Lena Maxe at SGU, Britt-Marie Pott and Christina Hansson at Sydvatten, Mikael Areskoug at VASYD and Lilian Rundström at NSVA.

Disclosure statement

No potential conflict of interest was reported by the authors.