Joint Spatio-temporal Shared Component Model with an Application in Iran Cancer Data

Abstract

Background: Among the proposals for joint disease mapping, the shared component model has become more<br />popular. Another advance to strengthen inference of disease data is the extension of purely spatial models to include<br />time aspect. We aim to combine the idea of multivariate shared components with spatio-temporal modelling in a joint<br />disease mapping model and apply it for incidence rates of seven prevalent cancers in Iran which together account for<br />approximately 50% of all cancers. Methods: In the proposed model, each component is shared by different subsets<br />of diseases, spatial and temporal trends are considered for each component, and the relative weight of these trends for<br />each component for each relevant disease can be estimated. Results: For esophagus and stomach cancers the Northern<br />provinces was the area of high risk. For colorectal cancer Gilan, Semnan, Fars, Isfahan, Yazd and East-Azerbaijan<br />were the highest risk provinces. For bladder and lung cancer, the northwest were the highest risk area. For prostate and<br />breast cancers, Isfahan, Yazd, Fars, Tehran, Semnan, Mazandaran and Khorasane-Razavi were the highest risk part.<br />The smoking component, shared by esophagus, stomach, bladder and lung, had more effect in Gilan, Mazandaran,<br />Chaharmahal and Bakhtiari, Kohgilouyeh and Boyerahmad, Ardebil and Tehran provinces, in turn. For overweight<br />and obesity component, shared by esophagus, colorectal, prostate and breast cancers the largest effect was found for<br />Tehran, Khorasane-Razavi, Semnan, Yazd, Isfahan, Fars, Mazandaran and Gilan, in turn. For low physical activity<br />component, shared by colorectal and breast cancers North-Khorasan, Ardebil, Golestan, Ilam, Khorasane-Razavi and<br />South-Khorasan had the largest effects, in turn. The smoking component is significantly more important for stomach<br />than for esophagus, bladder and lung. The overweight and obesity had significantly more effect for colorectal than of<br />esophagus cancer. Conclusions: The presented model is a valuable model to model geographical and temporal variation<br />among diseases and has some interesting potential features and benefits over other joint models.