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Smoking cessation and mortality among middle-aged and elderly Chinese in Singapore: the Singapore Chinese Health Study
  1. Sin How Lim1,
  2. Bee Choo Tai1,
  3. Jian-Min Yuan2,3,4,
  4. Mimi C Yu2,3,
  5. Woon-Puay Koh1
  1. 1Saw Swee Hock School of Public Health, National University of Singapore, Singapore, Singapore
  2. 2Division of Cancer Control and Population Sciences, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania, USA
  3. 3Department of Epidemiology, University of Pittsburgh Graduate School of Public Health, Pittsburgh, Pennsylvania, USA
  4. 4The Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota, USA
  1. Correspondence to Dr Woon-Puay Koh, Saw Swee Hock School of Public Health, National University of Singapore, MD3, 16 Medical Drive, Singapore 117597, Singapore; woon_puay_koh{at}nuhs.edu.sg

Abstract

Objective This study determines if recent smoking cessation, compared with long-term cessation, can reduce mortality risk associated with smoking.

Methods Data from the Singapore Chinese Health Study, a cohort study of middle-aged and elderly Chinese in Singapore, were analysed (n=48 251). Smoking status was evaluated at recruitment between 1993 and 1998 and reassessed between 1999 and 2004. Participants were classified as never-smokers, long-term quitters (quit before recruitment, mean 17.0 years), new quitters (quit between recruitment and second interview, mean 4.3 years) and current smokers. Mortality was ascertained by linkage with the nationwide death registry.

Results After a mean follow-up of 8.1 years, 6003 deaths had occurred by 31 December 2009. Compared with current smokers, the adjusted HR (95% CI) for total mortality was 0.84 (0.76 to 0.94) for new quitters, 0.61 (0.56 to 0.67) for long-term quitters and 0.49 (0.46 to 0.53) for never-smokers. New quitters had 24% reduction in lung cancer mortality (HR: 0.76, 95% CI 0.57 to 1.00) and long-term quitters had 56% reduction (HR: 0.44, 95% CI 0.35 to 0.57). Risk for coronary heart disease mortality was reduced in new quitters (HR: 0.84, 95% CI 0.66 to 1.08) and long-term quitters (HR: 0.63, 95% CI 0.52 to 0.77), although the result for new quitters was of borderline significance due to relatively small number of cardiovascular deaths. Risk for chronic pulmonary disease mortality was reduced in long-term quitters but increased in new quitters.

Conclusion Significant reduction in risk of total mortality, specifically for lung cancer mortality, can be achieved within 5 years of smoking cessation.

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Footnotes

  • Funding This study is supported by the National Institutes of Health (grant numbers R01-CA55069, R35-CA53890, R01-CA80205 and R01-CA144034).

  • Competing interests None.

  • Ethics approval The Institutional Review Boards at the National University of Singapore and the University of Minnesota.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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