Hodgkin Lymphoma has a seasonal pattern of incidence and mortality that depends on latitude

Seasonal variations in incidence and mortality after a Hodgkin lymphoma (HL) diagnosis have been previously described with partly conflicting results. The goal of this analysis is to provide a comprehensive analysis of these seasonal variations. In total, 41,405 HL cases diagnosed between 1973 and 2012 in the 18 Surveillance, Epidemiology, and End Results registries were included. Cosinor analysis and Cox proportional-hazards models were employed to analyze seasonality of incidence and mortality, respectively. HL shows a sinusoid seasonal incidence pattern (p < 0.001). Estimated incidence in March is 15.4% [95%-CI: 10.8-20.0] higher than in September. This sinusoid pattern is more pronounced at higher latitudes (p = 0.023). The risk of dying within the first three years after a HL diagnosis in winter is significantly increased compared to a HL diagnosis in summer at higher latitudes (HR = 1.082 [95%-CI: 1.009-1.161], p = 0.027). Furthermore, increasing northern latitude increases the additional mortality risk conferred by a diagnosis in winter (p(interaction)0.033). The seasonality patterns presented here provide epidemiological evidence that Vitamin D might play a protective role in HL. Further evidence on the direct association between Vitamin D levels and the clinical course of HL needs to be collected to advance the understanding of the role of Vitamin D in HL.