Regional variations in oral cancer incidence in Ireland

Oral cancer has anecdotally been held to have a regional distribution in Ireland, with higher incidence rates in western areas. The first all-Ireland data sets on oral cancer incidence rates were recently published by cancer registries in Northern Ireland and the Republic of Ireland, for the years 1994-1998 and 1994-1997 respectively. The objective of this study was to analyse these rates according to the 12 health administrative regions on the island of Ireland. All rates were standardised to the world population using standard methodology, and were examined separately for lip, intra-oral, salivary and pharyngeal cancers for men and for women. Rates were mapped to highlight any regional variations. In general, the anecdotal evidence for higher incidences in the west of Ireland has not been borne out, except for lip cancers in men, which in turn is reflected in the slight western preponderance in the distribution of all oral cancers. The incidences of intra-oral cancers in both men and women were highest in the regions that include the two large conurbations (Belfast and Dublin). We conclude that the anecdotal evidence for a higher incidence of oral cancer in the west of Ireland was probably based on the distorting effect of the high incidences of lip cancer in men in these regions.