Spatial Association between Gastric Cancer Mortality and Goiter in Sardinia

Background: Gastric cancer (GC) is the third leading cause of cancer mortality worldwide. The incidence of GC varies between countries according to exposure to different risk factors. Hypothyroidism has been suggested as a potential GC risk factor. In Sardinia, Italy, the prevalence of endemic goiter is high and GC mortality is unevenly distributed. This ecological study aimed to investigate GC mortality and its relationship with hypothyroidism, adjusting for potential confounders.
Methods: The spatial association between GC mortality and goiter (a proxy of hypothyroidism), diet, stature and pastoralism (a proxy of Helicobacter pylori infection), available at the aggregated level, was modelled in the island's 377 municipalities, separately by sex, using geographically weighted regression (GWR).
Results: The GC standardized mortality ratio ranged from 0.0 to 10.4 across municipalities. A hotspot of GC mortality was detected in the central mountainous area of Sardinia among males, positively associated with goiter (GWR estimate 0.213 ± 0.122), and the practice of sheep‒rearing (GWR estimate 0.127 ± 0.080), whereas a negative association with the diet score (GWR estimate 0.032 ± 0.034), and null for stature were found. No significant associations were found in females.
Conclusion: Within the limitations of ecological studies goiter prevalence was an independent predictor of GC mortality in males.