NORTH-SOUTH GRADIENT IN INCIDENCE OF JUVENILE-ONSET IBD IN SCOTLAND
Gastrointestinal Unit, University Department of Medical Sciences, Western General Hospital, Edinburgh, UK
Introduction: The north-south gradient of IBD incidence was first described in Europe but the recent EC-IBD study suggests that the difference is narrowing. We and others have shown a high and rising Scottish incidence of IBD in the <16 age range, and using our unique dataset now aim to assess its variation with latitude.
Methods: The Scottish hospital-discharges-linked database was used to identify 933 patients less than 19 years old who were ICD coded as having had IBD between 1981 and 1995. All case records were reviewed, diagnoses confirmed and postcode at symptom onset noted. Incident cases (580) were those with symptom onset up to 16 years of age within the period 1 January 1981 to 31 December 1995. Incidence rates were calculated per 100 000 population per year for each of the 15 Scottish postcode districts and were standardised to the 1991 census population. The latitude of the principal town in each postcode district was used.
Results: The highest sex standardised incidence was found in the Shetland isles (7.62, latitude 60°, 9'N), this was followed by Orkney/NE Scotland (6.64, latitude 58°, 59') The lowest incidence occurred in the Motherwell district (2.36, latitude 55°48'N). The r2 value for the correlation between latitude and incidence is 0.71.
Conclusion: The high incidence of IBD in NE Scotland is consistent with Kyles' previous data, in addition we have shown a marked north south gradient in the incidence of juvenile-onset IBD in Scotland. The mechanism underlying this geographical pattern remains uncertain.