Time and space co-ordinates of Hodgkin's lymphoma in Sardinia, Italy

Background: The epidemiological investigation of Hodgkin's lymphoma (HL) among the genetically peculiar population of the Italian island of Sardinia might provide interesting etiological clues. Methods: We used the database of 1974–2003 incident cases of hematological malignancies in Sardinia and Bayesian methods to explore the time trend and geographic spread of HL incidence by sex, and age whether ≤44 or ≥45 years. We also tested its association with several socio-economic and environmental risk factors. Results: The age- and sex-standardized (world population) incidence rate of HL was 2.6 per 100,000 (95% CI, 2.5–2.8). Over the study period, HL incidence increased linearly in both sexes and among those aged ≤44 years but not above that age. Cases clustered among young women in a central-western area covering four bordering administrative units (13 cases vs. 5.7 expected, P = 0.002). The posterior probability of excess HL cases aged ≤44 years was elevated only in a commune in the suburban area of the region's capital. Cases aged ≥45 years were uniformly spread over the region. Among the risk factors we explored, urban residence was associated with an elevated and goat farming with a decreased risk of HL occurrence. We did not observe a link with socio-economic deprivation, environmental exposures, or multiple sclerosis. The geographic spread of COVID-19 was also unrelated to past HL incidence. Conclusions: Our results prompt further in-depth investigation into the previously undetected cluster and the nature of the observed associations.