Spatial distribution and disease ecology of gastric cancer in western Honduras.

摘要

Gastric cancer, etiologically linked to infection with Helicobacter pylori, is the leading infectious-related cancer and the second most common cause of cancer mortality worldwide. Previous research has shown that gastric cancer rates are higher at high altitudes; however causal factors remain poorly understood. This research examines the relationship between altitude and gastric cancer risk, and explores potential explanatory covariates related to human behavior that may help explain the spatial patterns of gastric cancer incidence. Using a case control study of gastric cancer cases in western Honduras from 2002-2012, clusters of high-incidence areas are identified. Binomial multilevel likelihood models are constructed to better understand how altitude affects gastric cancer risk and to explore how individual-level behaviors drive disease incidence patterns. While simple models often assume all individuals are identical, multilevel models incorporate individual and group-level heterogeneity in characteristics that may be related to disease dynamics. Results indicate that age-standardized rates (n=594) are twice as high for males than females (15.07 for males and 6.59 for females), and that high rates are significantly clustered at the municipio (local administrative unit) level. Altitude was an insignificant predictor of gastric cancer when measured both as a continuous (p=0.197) and categorical variable (high/low; p=0.192). The results of the multilevel modeling of individual-level behaviors reveal that use of refrigeration as an adult is associated with a decrease in gastric cancer risk (beta = -0.9883, p=6.51e-08). The finding that altitude does not affect gastric cancer risk within the study area suggests the possibility that the study area does not contain enough altitudinal heterogeneity to accurately characterize the relationship between altitude and gastric cancer rates. The finding that use of refrigeration as an adult is protective against gastric cancer suggests that access to refrigeration may decrease dependency on salted and preserved meats and increase access to fruits and vegetables, two established factors related to gastric cancer risk. During the past two decades it has been well-established that infection with H. pylori is linked to increased gastric cancer risk. However, the finding that individual-level behavior impacts disease risk supports the theory that to understand disease dynamics, host-pathogen interactions must be considered within the context of their disease ecology.