Lumping or splitting: seeking the preferred areal unit for health geography studies

BACKGROUND: Findings are compared on geographic variation of incident and late-stage cancers across Connecticut using different areal units for analysis. RESULTS: Few differences in results were found for analyses across areal units. Global clustering of incident prostate and breast cancer cases was apparent regardless of the level of geography used. The test for local clustering found approximately the same locales, populations at risk and estimated effects. However, some discrepancies were uncovered. CONCLUSION: In the absence of conditions calling for surveillance of small area cancer clusters ('hot spots'), the rationale for accepting the burdens of preparing data at levels of geography finer than the census tract may not be compelling.