Geographic distribution and demographic correlates of colorectal cancer mortality in Sydney, New South Wales.

Colorectal cancer (CC) has the highest incidence of any internal malignancy in Australia and is a major cause of death. A knowledge of the geographic distribution of CC will aid in the identification of high risk groups for whom diagnostic and treatment facilities should be provided and may give clues to aetiological factors. Total CC deaths and age-standardized mortality ratios for Local Government Areas in Sydney, Australia were mapped and the relationships between mortality and selected demographic measures were examined. Several statistically significant zero-order correlation coefficients were found but multiple regression analysis showed a dominant independent negative effect of distance from the centre of the city on CC mortality. No substantial independent effects of demographic variables were observed. The existence of presently unmeasured environmental aetiological factors is postulated.