Incidence of non-Hodgkin's lymphoma and Hodgkin's disease in Sardinia, Italy: 1974-1993

Abstract

BACKGROUND AND OBJECTIVES: The reasons for the worldwide increase in non-Hodgkin's lymphoma (NHL) are not clearly understood. We investigated whether an increasing trend over time has also occurred in the Italian region of Sardinia, the population of which exhibits peculiar genetic features, due to millenary isolation and pressure from 2,500 years of malarial endemism. We also investigated the geographic variation in NHL risk within the region. DESIGN AND METHODS: We designed a descriptive epidemiology study of NHL among the Sardinian population by following up the incidence of this disease in the period 1974-1993. We calculated the standardized incidence rate (SIR) of NHL by year for the total population and by gender. The time trend of Hodgkin's disease (HD) was also evaluated as a comparison term and for validation purposes. We also mapped NHL risk in the 361 administrative units (communes) of the region. RESULTS: NHL incidence in the Sardinian population over the whole study period was 7.5 x 10(-5) year(-1) (men: 8.2; women: 6.7), and increased from 4.1 in 1974 to 9.1 in 1993. The increasing trend was consistent by gender, and mostly affected subjects aged 55 years or older. Nodal and extra-nodal forms of NHL shared the same pattern of increasing incidence. Excluding the few NHL cases related to AIDS did not change the results. No such pattern was observed for HD incidence. The NHL incidence rate (age > or = 25 years) ranged from 0.0-60.0 x 10(-5) year-1 across communes. Areas at risk were located mainly in the northern part of the region, but risk among men was also elevated in the major urban area in southern Sardinia. INTERPRETATION AND CONCLUSIONS: Our study shows that NHL incidence increased 2.2-fold in Sardinia from 1974 to 1993, a finding which is consistent with other world-wide report. The risk has risen in a few areas, mainly in central and northern Sardinia and in the major urban areas. Analytic studies are under way to investigate a broad range of risk factors, including viral, occupational, and environmental factors, that might account for our results.