Heliophysical activity and incidence variations of skin malignant melanoma in Czechoslovakia: a regional study.

Cyclic variations in the incidence of skin malignant melanoma during the years 1964-1985 in East Bohemia (excluding the districts of Pardubice and Svitavy), Czechoslovakia have been studied, as linear correlations with solar activity indexes have been revealed. The following statistical methods were applied: periodogram regression analysis, phase-correlation analysis, sigma-method and Student's t-test. The discretization of the data is on the basis of 1 year. Different cycles were found in the incidence variations (T = 7.5 years, T = 11.5 years, etc.), and this has been correlated with the variations of two heliophysical indexes (sigma, W) for the same time period. A few significant statistical relationships have been established with a time difference (lag-period) between the extremes of the data series; the incidence maxima follow the peaks of solar activity and appear about the minima of solar indexes, mainly.