| Summary: | Background: Although some classic risk factors of NPC such as salted fish, tobacco and vegetable consumption were established a few decades ago, no convincing evidence that the decreasing trend in NPC incidence and mortality rates seen in most parts of the world could be explained by the changes of these consumption. As different histological types and age groups may have distinct risk factor profile in NPC development, it is important to look at incidence and mortality trends across different jurisdictions before any further individual studies are carried out worldwide.
Objectives: With the focus on both high and low risk areas, this study aimed to 1) examine the descriptive epidemiology of NPC, including the secular trends of age-standardised incidence rate (ASIR), age-standardised mortality rate (ASMR) and age-specific incidence and mortality rate by sex; 2) perform an ecologic analysis between ASIR, ASMR and classical exposures. This included a multi-jurisdiction comparison between ASIR, ASMR and salted fish, cigarette and vegetable consumption per capita and 3) investigate the secular trend of ASIR and ASMR by sex, age and histologic subtype.
Methods: NPC ASMR was obtained from the WHO cancer mortality database and ASIR, age-subtype specific incidence and mortality rates were provided by various cancer registries. All age and subtype specific rates were plotted in every 5 calendar years. Per capita consumption of salted fish, tobacco and vegetables in 8 regions (Hong Kong, China, Finland, Japan, Portugal, Singapore, United Kingdom and United States) were obtained from the Food and Agriculture Organization of the United Nation (FAO) and from different corresponding governmental departments. Pearson correlation coefficients and multivariate regression analysis were performed to examine both crude and adjusted associations.
Results: There were markedly decreasing trends of NPC ASIR and ASMR in most of the high risk areas over the past three decades, while only some declines in incidence and mortality rates was observed in low risk areas. No association was found between salted fish, vegetable consumption and ASMR or ASIR in any region, except in Hong Kong where lag year cigarette consumption in males was correlated with ASIR (Pearson r for 10 lag year = 0.680; 15 lag year = 0.739 and 20 lag year = 0.747, all p<0.05). Multivariate regression analysis did not show association with any of the consumption in Japan, Portugal, the US and the UK. An earlier age of onset around 45-50 was observed with non-keratinizing carcinoma as the dominant subtype in high risk areas, while in low risk area the peak age was not seen until after 60 years old with most of the cases being keratinizing NPC. Conclusions: There were distinct differences in risk profile between NPC age-standardised and age-subtype specific rates between high and low risk areas. With the general secular trends of NPC incidence and mortality rates by age and tumour type being revealed in this study, further exploration in other jurisdictions with different potential risk or protective factor is warranted. === published_or_final_version === Public Health === Master === Master of Philosophy
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