Non-Hodgkin's lymphoma in US children: biometeorological approach

Previous studies have shown cyclicity in the incidence of malignant melanoma of the skin (Houghton e.a. 1981, Dimitrov 1998, etc.) and associations of such variations with heliogeophysical activity (HGA). The purpose of this study was to investigate trends and patterns of variations in the incidence of non-Hodgkin's lymphoma (NHL) in US children (1973-1989) and their possible relationships to variations in HGA (Rz-index, aa-index). Linear and non-linear regression, autocorrelation, periodogram regression analysis and phase-correlation analysis were applied. No significant trend in incidence of NHL has been found but high-frequency cyclic patterns of variations were revealed (period T = 4 years, p < 0.05). Similar cyclicity has been described also in HGA (period T = 5 divided by 6 years, p < 0.05). Lag-periods in associations of NHL incidence with Rz-index and aa-index have been described--dT = 6, 8, 10, 12 and 12 years, respectively (p < 0.05). To conclude, maximal rates of NHL incidence are most likely to appear on the descending slopes and about minima of HGA cycles, i.e. out of phase. Our results are consistent with the hypothesis of positive associations between incidence of non-Hodgkin's lymphoma and solar phenomena (Cartwright e.a. 1994, etc.)