HIGH SMOKING, LOW MORTALITY: UNPACKING THE PARADOX OF COPD OUTCOMES IN JAPAN AND THE UNITED KINGDOM

Abstract

Chronic Obstructive Pulmonary Disease (COPD) is a significant cause of mortality and morbidity worldwide with tobacco exposure being a major risk factor. However, Japan demonstrates a significantly lower COPD mortality despite historically higher tobacco consumption than the United Kingdom creating a paradoxical mortality pattern. This study aims to explore this pattern by: (1) comparing the COPD mortality rates, (2) cigarette sales trends, (3) gender differences in smoking prevalences, (4) comparing dietary factors (5) comparing genetic factors, and (6) comparing the diagnosis methods of COPD of the two countries in order to determine the biological, behavioural and health-system contributors to this paradox. A narrative literature review was conducted using PubMed, Scopus and open-access databases, with priority given to national-level epidemiological data with standardised diagnostic criteria for COPD. Demographic and environmental indicators, such as age-standardised COPD mortality, cigarette sales, sex-specific smoking prevalence and dietary composition were acquired from Our World In Data and open-access repositories. Japan demonstrated consistently lower chronic respiratory disease mortality despite significantly higher tobacco consumption per adult in the form of cigarette sales. Sex-specific smoking patterns differed greatly, with Japan showing a much wider male-to-female smoking disparity whereas proportions were significantly more balanced between men and women in the UK. Japan’s dietary pattern followed a more plant and fish-based profile compared with the UK, alongside lower total consumption of meat and saturated fat. Japan also had a higher frequency of loss-of-function CYP2A6 *4 affecting nicotine metabolism and COPD outcomes, although the exact prevalence in the UK cannot be currently quantified from current data. Japan exhibited significant underdiagnosis of COPD compared to the UK, potentially influencing the accuracy of reported COPD incidence and mortality. Therefore, despite higher rates of smoking since 1971, COPD mortality rate has been historically lower in Japan than the United Kingdom. Further investigation into the factors leading to this paradox could help improve national strategies for COPD risk reduction.