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 0.2/10 5 in some Asian countries to over 80/10 5 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 Â 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 16.4/10 5 , range 13.6-17.9 and 25.3/10 5 , 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.

A nationwide cohort study of the incidence of inflammatory bowel disease in Sweden from 1990 to 2014

“…We used the 2014 Swedish total population as standard population, while the regional study used the 1999 regional population. Another study found evidence of significant regional differences in prevalence between municipalities in the south of Sweden 32 . We cannot determine if differences between our study and the regional study are caused by different methodology and case definitions or existing regional differences affecting the temporal trends and IRs.…”

“…Another study found evidence of significant regional differences in prevalence between municipalities in the south of Sweden. 32 We cannot determine if differences between our study and the regional study are caused by different methodology and case definitions or existing regional differences affecting the temporal trends and IRs. The contradicting findings indicate a need to further investigate regional differences and underlying reasons for such.…”

The Role of the Urban Exposome in the Increasing Global Rates of Pediatric Inflammatory Bowel Disease

“…A Norwegian study reported higher IBD incidence rates in areas supplied with water that was high in iron (adjusted relative risk [RR] 1.17, 95% CI 1.06-1.30) and with higher pH (adjusted RR 1.02, 95% CI 1.01-1.03) (19). In contrast, a Swedish study found no association between IBD incidence and water composition/ quality (20). Although highly variable, all water measurements in the Swedish study were within ranges specified by the National Food Agency of Sweden while some measurements in the Norwegian study exceeded the limits allowed by the Drinking Water Act.…”

“…The association between drinking water composition and IBD is inconclusive. Two Scandinavian studies, including individuals living in both urban and rural areas, evaluated several components of water composition, including iron, pH, aluminum, coliform bacteria, color, turbulence, alkalinity (HCO 3 ), nitrate (NO 3 ), sulphate (SO 4 ), magnesium, and/or calcium (19,20). A Norwegian study reported higher IBD incidence rates in areas supplied with water that was high in iron (adjusted relative risk [RR] 1.17, 95% CI 1.06–1.30) and with higher pH (adjusted RR 1.02, 95% CI 1.01–1.03) (19).…”