thesis

Bayesian spatio-temporal modelling of tobacco-related cancer data in Switzerland

Abstract

Tobacco use is the leading cause of preventable death worldwide. Each year the tobacco epidemic accounts for 6 million deaths and costs hundreds of billions of dollars to the economy. Cigarette smoking accounts for more deaths than AIDS, murder, legal and illegal drugs, road accidents and suicide combined. Around 85–90% of all lung cancer deaths are estimated to be attributed to active or passive smoking. In Switzerland, lung cancer is the first cause of cancer mortality in men and second in women (after breast cancer). Gender-specific smoking patterns differ essentially in time as well as in space. In the 19th and the beginning of the following century, smoking was restricted to the male population, finding its peak in the 1970s in most European countries. In the past, the image of female tobacco use experienced an essential turn. In the middle of the 20th century the smoking prevalence among women increased due to the changes in gender roles and the subsequent effect on female smoking reputation. Before, female smoking had not been socially accepted. After strong gender-related developments, female smoking was associated with independence, emancipation and freedom. This movement was exploited to a great extent by the tobacco industry by adjusting their marketing strategies regarding this new target audience. In many developed countries the gap between gender and smoking prevalence is closing since the last decades, as males are smoking less, while female tobacco smoking is increasing steadily. Information on spatial as well as temporal patterns and trends of a disease are essential for health planning and intervention purposes. The Swiss Federal Office of Public Health (FOPH) has launched the National Programme Tobacco 2008–2012 aiming to reduce the proportion of smokers, targeting a decline of tobacco-related morbidity and mortality in the country as a final result. Cancer mapping visualizes geographical and temporal patterns and trends. Maps of estimated mortality serve as helpful tools to identify high risk areas and therefore enable focused intervention planning at a higher geographical scale than the national one. Disease maps of crude rates can be non-informative and might even lead to misinterpretation, as rare diseases or small populations might dominate the map and result in large variability in the estimated rates. Distinction between chance and real difference of the obtained variability is challenging. Spatial modelling of the rates enables the assessment of covariate effects to explain observed patterns and highlight them by obtaining smooth maps. Bayesian methods are the state-of-the-art modelling approach for spatio-temporal analysis. They allow flexible modelling and inference and provide computational advantages via the implementation of Markov chain Monte Carlo (MCMC). Model formulations improve the estimates sparse, unstable rates by borrowing strength from their neighbours. In addition, they allow risk factor analysis which takes into account potential spatial correlation. Apart flexible modelling, Bayesian inference provide computational advantages via the implementation of Markov chain Monte Carlo simulation methods. This thesis aimed (i) to assess geographical differences and trends of age- and gender-specific lung and all tobacco-related cancer mortality in Switzerland; (ii) to project tobacco-related cancer mortality in Switzerland at different geographical levels accounting for spatial variation; (iii) to develop Bayesian age-period-cohort (APC) models for projecting cancer mortality data; (iv) to develop Bayesian back-calculation models to estimate age- and gender-specific incidence from sparse mortality data; and (v) to develop models to indirectly approximate gender-specific smoking patterns in space and time by unadjusted and adjusted lung cancer mortality rates with non-smoking risk factors

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