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Cancer incidence on a small island--research opportunities in general practice.

OBJECTIVE
To test the impression of an increased cancer incidence on the island of Pellworm (in the far North of Germany) and to illustrate the feasibility of a general practice-based approach in epidemiological research.


DESIGN
Cancer incidence on Pellworm was prospectively registered in the only general practice on the island from 1986 to 1992. Age-standardized rates and expected rates were calculated on the basis of the Saarland cancer registry, the only registry in Germany. Standardized incidence ratios and 95% confidence intervals (CI) for Poisson-distributed events were also calculated. The cancer data were summed up over a seven-year period.


SETTING
The only general practice on the island of Pellworm, a North Frisian marshland-island.


SUBJECTS
The total practice population between 1986 and 1992 (N = 1172)


RESULTS
The crude annual cancer incidence rate for Pellworm was, according to the impression, unexpectedly high: 634/100 000 for men and 502/100 000 for women. After age standardization, however, this increased rate of cancer incidence was even lower than in the Saarland (ratios: 0.86 for men and 0.95 for women). Only the incidence of neoplasms of the lymphatic and haematopoietic tissue in men exceeded the limits of statistical likelihood (ratio: 3.21; 95% CI: 1.17-7.10).


CONCLUSION
The impression of an increased rate of cancer on Pellworm could not be validated. The overall incidence rate was even lower than expected. Only the rate of leukaemia/lymphoma (men) was significantly higher. Reasons for this result could not be detected by a descriptive approach. General practice is a suitable place for studies in cancer epidemiology, especially in such ideal circumstances as a clearly limited area and complete and reliable documentation.