Thirunavukkarasu Sathish1, Koon K Teo1, Philip Britz-McKibbin2, Biban Gill2, Shofiqul Islam1, Guillaume Paré3, Sumathy Rangarajan1, MyLinh Duong1, Fernando Lanas4, Patricio Lopez-Jaramillo5, Prem K Mony6, Lakshmi Pinnaka7, Vellappillil Raman Kutty8, Andres Orlandini9, Alvaro Avezum10, Andreas Wielgosz11, Paul Poirier12, Khalid F Alhabib13, Ahmet Temizhan14, Jephat Chifamba15, Karen Yeates16, Iolanthé M Kruger17, Rasha Khatib18, Rita Yusuf19, Annika Rosengren20, Katarzyna Zatonska21, Romaina Iqbal22, Weida Lui23, Xinyue Lang23, Sidong Li23, Bo Hu23, Antonio L Dans24, Afzal Hussein Yusufali25, Ahmad Bahonar26, Martin J O'Donnell1, Martin McKee27, Salim Yusuf28. 1. Population Health Research Institute, McMaster University and Hamilton Health Sciences, Hamilton, ON, Canada. 2. Department of Chemistry and Chemical Biology, McMaster University, Hamilton, ON, Canada. 3. Population Health Research Institute, McMaster University and Hamilton Health Sciences, Hamilton, ON, Canada; Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada. 4. Internal Medicine Department, Universidad de La Frontera, Temuco, Chile. 5. Masira Research Institute, Medical School, Universidad de Santander, Bucaramanga, Colombia. 6. Division of Epidemiology & Population Health, St John's Medical College & Research Institute, Bangalore, India. 7. Department of Community Medicine & School of Public Health, Post Graduate Institute of Medical Education & Research, Chandigarh, India. 8. Health Action by People, Thiruvananthapuram, Kerala, India. 9. ECLA Foundation, Instituto Cardiovascular de Rosario, Rosario, Argentina. 10. International Research Center, Hospital Alemão Oswaldo Cruz, São Paulo, Brazil. 11. Department of Medicine, University of Ottawa, Ottawa, ON, Canada. 12. Faculty of Pharmacy, Institut universitaire de cardiologie et de pneumologie de Québec, Université Laval, Queébec, QC, Canada. 13. Department of Cardiac Sciences, King Fahad Cardiac Center, College of Medicine, King Saud University, Riyadh, Saudi Arabia. 14. Cardiology Department, Ankara City Hospital, Ankara, Turkey. 15. Department of Physiology, University of Zimbabwe College of Health Sciences, Harare, Zimbabwe. 16. Department of Medicine, Queen's University, Kingston, ON, Canada. 17. Africa Unit for Transdisciplinary Health Research, North-West University, Potchefstroom, South Africa. 18. Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA. 19. Department of Life Sciences, Independent University Bangladesh, Dhaka, Bangladesh. 20. Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden; Region Västra Götaland, Sahlgrenska University Hospital, Gothenburg, Sweden. 21. Department of Social Medicine, Wroclaw Medical University, Wroclaw, Poland. 22. Department of Community Health Sciences, Aga Khan University, Karachi, Pakistan. 23. Medical Research and Biometrics Center, Fuwai Hospital, National Center for Cardiovascular Diseases, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China. 24. Department of Medicine, University of the Philippines College of Medicine, Manila, Philippines. 25. Hatta Hospital, Dubai Medical University, Dubai Health Authority, Dubai, United Arab Emirates. 26. Isfahan Cardiovascular Research Center, Cardiovascular Research Institute, Isfahan University of Medical Sciences, Isfahan, Iran. 27. Department of Health Services Research and Policy, London School of Hygiene & Tropical Medicine, London, UK. 28. Population Health Research Institute, McMaster University and Hamilton Health Sciences, Hamilton, ON, Canada. Electronic address: yusufs@mcmaster.ca.
Abstract
BACKGROUND: Separate studies suggest that the risks from smoking might vary between high-income (HICs), middle-income (MICs), and low-income (LICs) countries, but this has not yet been systematically examined within a single study using standardised approaches. We examined the variations in risks from smoking across different country income groups and some of their potential reasons. METHODS: We analysed data from 134 909 participants from 21 countries followed up for a median of 11·3 years in the Prospective Urban Rural Epidemiology (PURE) cohort study; 9711 participants with myocardial infarction and 11 362 controls from 52 countries in the INTERHEART case-control study; and 11 580 participants with stroke and 11 331 controls from 32 countries in the INTERSTROKE case-control study. In PURE, all-cause mortality, major cardiovascular disease, cancers, respiratory diseases, and their composite were the primary outcomes for this analysis. Biochemical verification of urinary total nicotine equivalent was done in a substudy of 1000 participants in PURE. FINDINGS: In PURE, the adjusted hazard ratio (HR) for the composite outcome in current smokers (vs never smokers) was higher in HICs (HR 1·87, 95% CI 1·65-2·12) than in MICs (1·41, 1·34-1·49) and LICs (1·35, 1·25-1·46; interaction p<0·0001). Similar patterns were observed for each component of the composite outcome in PURE, myocardial infarction in INTERHEART, and stroke in INTERSTROKE. The median levels of tar, nicotine, and carbon monoxide displayed on the cigarette packs from PURE HICs were higher than those on the packs from MICs. In PURE, the proportion of never smokers reporting high second-hand smoke exposure (≥1 times/day) was 6·3% in HICs, 23·2% in MICs, and 14·0% in LICs. The adjusted geometric mean total nicotine equivalent was higher among current smokers in HICs (47·2 μM) than in MICs (31·1 μM) and LICs (25·2 μM; ANCOVA p<0·0001). By contrast, it was higher among never smokers in LICs (18·8 μM) and MICs (11·3 μM) than in HICs (5·0 μM; ANCOVA p=0·0001). INTERPRETATION: The variations in risks from smoking between country income groups are probably related to the higher exposure of tobacco-derived toxicants among smokers in HICs and higher rates of high second-hand smoke exposure among never smokers in MICs and LICs. FUNDING: Full funding sources are listed at the end of the paper (see Acknowledgments).
BACKGROUND: Separate studies suggest that the risks from smoking might vary between high-income (HICs), middle-income (MICs), and low-income (LICs) countries, but this has not yet been systematically examined within a single study using standardised approaches. We examined the variations in risks from smoking across different country income groups and some of their potential reasons. METHODS: We analysed data from 134 909 participants from 21 countries followed up for a median of 11·3 years in the Prospective Urban Rural Epidemiology (PURE) cohort study; 9711 participants with myocardial infarction and 11 362 controls from 52 countries in the INTERHEART case-control study; and 11 580 participants with stroke and 11 331 controls from 32 countries in the INTERSTROKE case-control study. In PURE, all-cause mortality, major cardiovascular disease, cancers, respiratory diseases, and their composite were the primary outcomes for this analysis. Biochemical verification of urinary total nicotine equivalent was done in a substudy of 1000 participants in PURE. FINDINGS: In PURE, the adjusted hazard ratio (HR) for the composite outcome in current smokers (vs never smokers) was higher in HICs (HR 1·87, 95% CI 1·65-2·12) than in MICs (1·41, 1·34-1·49) and LICs (1·35, 1·25-1·46; interaction p<0·0001). Similar patterns were observed for each component of the composite outcome in PURE, myocardial infarction in INTERHEART, and stroke in INTERSTROKE. The median levels of tar, nicotine, and carbon monoxide displayed on the cigarette packs from PURE HICs were higher than those on the packs from MICs. In PURE, the proportion of never smokers reporting high second-hand smoke exposure (≥1 times/day) was 6·3% in HICs, 23·2% in MICs, and 14·0% in LICs. The adjusted geometric mean total nicotine equivalent was higher among current smokers in HICs (47·2 μM) than in MICs (31·1 μM) and LICs (25·2 μM; ANCOVA p<0·0001). By contrast, it was higher among never smokers in LICs (18·8 μM) and MICs (11·3 μM) than in HICs (5·0 μM; ANCOVA p=0·0001). INTERPRETATION: The variations in risks from smoking between country income groups are probably related to the higher exposure of tobacco-derived toxicants among smokers in HICs and higher rates of high second-hand smoke exposure among never smokers in MICs and LICs. FUNDING: Full funding sources are listed at the end of the paper (see Acknowledgments).