Abstract
Current researches proposed the incident patterns and the related overweight risk factor for colon and oesophagus cancers. The incidence of these cancers was mapped using many methods such as stratified by sex or in general. This research models the geographical variation in the incidence of these two related cancers to investigate the relative importance of an overweight risk factor in Libya. Data on the incidence of colon cancer and oesophagus cancer between 2015 and 2020 were obtained from the African Oncology Institute, Sabratha, Libya. These data were recorded as new observations in 22 districts yearly. The Bayesian multivariate model or Bayesian shared component model for several diseases was applied to analyse the spatial variation of incidence rates jointly. In this research. the analysis shows that the joint method gives a better relative risk estimates compared with using the BYM model and mixture model. Between 2015 to 2020, the joint incidence rates of the two cancers were relatively high (0.5-1.5) in Libya. The multiple map explained that the western and southern parts of the country were at higher risk than other parts. The component representing overweigh had medium effect of colon and esophagus cancers. This incidence risk pattern has been obtained for the men but that for women have been a little different. Using a shared component model for joint modelling of incidence rates leads to more precise estimates than models of individual disease. A common risk factor (i.e., overweight) is important and needs more attention in the allocation and delivery of public health policies