The relationship between tobacco smoking, all-cause mortality, and premature death

In a cohort study published in BMC Public Health, researchers investigated smoking behavior and the potential association of tobacco smoke with premature death and all-cause mortality in China. 

They found that smoking status was associated with all-cause mortality and premature death, and pack-years of smoking correlated with premature death. The study emphasizes the adverse effects of smoking on public health in the country and calls for immediate action.

Study: Tobacco smoke and all-cause mortality and premature death in China: a cohort study. Image Credit: sruilk/Shutterstock.com

Background

Tobacco smoke is among the top two risk factors for mortality and caused 5.4 million deaths globally in 2006. As per the World Health Organization, at this rate, tobacco-related illnesses may claim more than eight million lives annually by 2030.

Predictions suggest that unless urgent measures are taken, developing nations may see an alarming 100% rise in tobacco-related deaths.

While the evidence demonstrates a strong association between tobacco smoke, mortality, and premature death in countries including the United States of America and the United Kingdom, there’s a shortage of cohort studies providing such evidence since 2010 in China.

The need for this research is especially critical as China reports the maximal prevalence of the use of tobacco among men, with millions of individuals exposed to passive smoking. Findings of a 15-year-long study suggest an association between smoking history, pack years of smoking, and mortality risk in rural China.

Therefore, researchers in the present study aimed to generate independent evidence starting from 2011 and examined the potential association between long-term smoking, premature death, and all-cause mortality in a nationally representative cohort.

About the study

Data from 16,701 individuals aged above 45 years in China was obtained from the national baseline database of the China Health and Retirement Longitudinal Study (CHARLS). CHARLS was a survey conducted in a nationwide cohort in which participants were followed up in waves (of two years each) until 2018.

Standard questionnaires were used to record the participant’s medical history (for hypertension, cardiovascular disease (CVD), dyslipidemia, and diabetes), ongoing treatment, and demographics. The interview status– dead or alive– was also noted in follow-ups.

The participants' smoking, drinking status, and body mass index (BMI) were noted. Participants were classified as non-smokers, ex-smokers, or smokers, and their smoking duration, pack-years, and age at starting and stopping smoking were recorded.

Deaths before 76.9 years for women and 72.7 years for men were considered premature. The statistical analysis included using Cox’s proportional hazards regression model, hazard ratio (HR), multivariable models, and estimating proportions, means, and p-values.

Results and discussion

A total of 367 deaths were noted in the 2013 follow-up of the study. The smoking prevalence was found to be higher in men (up to 52.68%) as compared to women (up to 9.72%).

Additionally, men showed a longer smoking duration (average 35.2 years), higher cigarette consumption (average 19.6 per day), and began smoking at a younger age (average 22.2 years) than women. Interestingly, the mean age of smoking cessation was found to be similar among men and women.

Baseline characteristics other than drinking status and residence status were similar among smoking and non-smoking men. Smoking women showed a higher prevalence of drinking and a history of cardiovascular conditions but a low prevalence of obesity.

The risk of premature death was found to be 1.6 times higher in current smokers and 2.3 times higher in ex-smokers, including men and women.

Additionally, the all-cause mortality risk was found to be 1.4 times higher in smokers and 1.8 times higher in ex-smokers. All-cause mortality risk was found to be higher in men than in women.

Individuals with ≥30 pack-years of smoking showed an increased risk of premature death as compared to non-smokers.

Although a correlative trend was observed between pack-years and premature death, no significant association was found between all-cause mortality. The age of starting and ceasing smoking did not show an association with premature death or all-cause mortality.

The study's findings are strengthened by its longitudinal design and minimal scope for bias. However, the study's limitations are the small sample size of observed deaths, the use of data only from the 2013 follow-up survey, and, more importantly, the lack of an understanding of the cause of deaths.

Conclusion

In conclusion, the present study provides contemporary evidence on the smoking habits of the Chinese population and reports an increased smoking prevalence among men. The findings confirm the association between tobacco smoking (in smokers as well as ex-smokers), premature death, and all-cause mortality.

The correlative trend observed between the number of pack-years of smoking and premature death highlights the importance of taking urgent steps to curb the detrimental impact of smoking on public health and educate the masses in that direction.

The outcomes of this study could help inform national and global policies that aim to reduce the prevalence of smoking, thereby improving health outcomes for the people of China and the world.

Written by

Dr. Sushama R. Chaphalkar

Dr. Sushama R. Chaphalkar is a senior researcher and academician based in Pune, India. She holds a PhD in Microbiology and comes with vast experience in research and education in Biotechnology. In her illustrious career spanning three decades and a half, she held prominent leadership positions in academia and industry. As the Founder-Director of a renowned Biotechnology institute, she worked extensively on high-end research projects of industrial significance, fostering a stronger bond between industry and academia.