Asian nations in early tobacco epidemic – Study

Asian countries are in the early stages of a tobacco smoking epidemic with habits mirroring those of the United States from past decades, setting the stage for a spike in future deaths from smoking-related diseases, writes Tom Wilemon for Vanderbilt University.

That’s the conclusion of researchers from Vanderbilt-Ingram Cancer Center and the Vanderbilt Epidemiology Center after analysing 20 prospective cohort studies from mainland China, Japan, South Korea, Singapore, Taiwan and India.

Using long-term follow-up data from those cohorts, the study – published in JAMA Network Open– is the largest investigation in Asian countries of birth cohort-specific and county- or region-specific smoking patterns and their association with deaths.

Future deaths are likely to echo the pattern that occurred in the United States as the popularity of smoking increased during and after World War II, which resulted in lung cancer mortality peaking around 1990, said Wei Zheng, MD, PhD, Anne Potter Wilson Professor of Medicine.

“There is about a 30-year gap or incubation period for the mortality to occur,” said Zheng, the study’s senior author. “Smoking takes about 20 or 30 years to have this full effect on lung cancer mortality.”

Tobacco control interventions may be having an effect on the smoking epidemic in some countries or areas because male smokers in the most recent birth cohort tended to quit smoking at younger ages.

“Asian countries that are richer, like Japan, South Korea and urban China, are doing a better job with this than rural China, India and other places,” said Danxia Yu, PhD, who is co-first author of the study along with Jae Jeong Yang, PhD, a visiting research fellow from the Seoul National University, South Korea.

Call for immediate action

The study calls for immediate actions for all Asian countries to implement comprehensive tobacco control policies, including raising tobacco taxes, implementing laws for smoke-free areas, banning tobacco advertising, requiring warning labels for tobacco products and providing help with quitting.

Older generations of Asians tended to start smoking later in life and smoke less than people in the United States did in past decades, Zheng said, but that behaviour pattern is changing.

“Younger people in more recent cohorts started smoking at a younger age, and they smoked a lot more,” Zheng said. “The deaths due to tobacco smoking also increased with this cohort.”

The researchers classified the birth cohorts by decades, ranging from pre-1910 to 1950 or later. Smoking accounted for 12.5% of all-cause mortality in the pre-1920 birth cohort, 21.1% in the 1920s cohort and 29.3% for the cohort born in 1930 or later. Lung cancer deaths attributable to smoking, which were 56.6% among men in the pre-1920s cohort, increased to 68.4% for men born in 1930 or later.

The researchers also studied cohorts with more recent data for men and women born in later decades to analyze smoking habits.

The rate for men in mainland China who have ever smoked has increased. Among Chinese men born in 1950 or later, 79.4% of those living in urban areas had smoked, and 74.3% of those in rural areas had. Traditionally, Japanese men have had the highest rate of having ever smoked.

Women in Asia have a much lower rate for smoking. The average percentage of women smokers for all 20 cohort studies was 7.8% compared to 65.4% for men.

Asia will face a growing burden of smoking-related health problems unless urgent tobacco control policies are implemented, the authors concluded.

Tobacco Smoking and Mortality in AsiaA Pooled Meta-analysis

JAMA Network Open. 2019; 2(3): e191474. 29 March 2019

doi:10.1001/jamanetworkopen.2019.1474

Jae Jeong Yang, PhD¹; Danxia Yu, PhD¹; Wanqing Wen, MD¹; et alXiao-Ou Shu, PhD¹; Eiko Saito, PhD²; Shafiur Rahman, MSc³; Prakash C. Gupta, PhD⁴; Jiang He, PhD⁵; Shoichiro Tsugane, PhD⁶; Yong-Bing Xiang, MD⁷; Yu-Tang Gao, MD⁷; Woon-Puay Koh, PhD^8,9; Akiko Tamakoshi, PhD¹⁰; Fujiko Irie, PhD¹¹; Atsuko Sadakane, PhD¹²; Ichiro Tsuji, PhD¹³; Seiki Kanemura, PhD¹³; Keitaro Matsuo, PhD^14,15; Chisato Nagata, PhD¹⁶; Chien-Jen Chen, ScD¹⁷; Jian-Min Yuan, PhD¹⁸; Myung-Hee Shin, PhD¹⁹; Sue K. Park, PhD^20,21,22; Wen-Harn Pan, PhD²³; You-Lin Qiao, PhD²⁴; Mangesh S. Pednekar, PhD⁴; Dongfeng Gu, PhD²⁵; Norie Sawada, PhD⁶; Hong-Lan Li, MD⁷; Jing Gao, MD⁷; Hui Cai, PhD¹; Eric Grant, PhD¹²; Yasutake Tomata, PhD¹³; Yumi Sugawara, PhD¹³; Hidemi Ito, PhD^14,15; Keiko Wada, PhD¹⁶; Chen-Yang Shen, PhD^26,27; Renwei Wang, MD¹⁸; Yoon-Ok Ahn, PhD²⁰; San-Lin You, PhD²⁸; Keun-Young Yoo, PhD^20,29; Habibul Ashan, MD^30,31,32; Kee Seng Chia, MD⁹; Paolo Boffetta, MD³³; Manami Inoue, PhD⁶; Daehee Kang, PhD^20,21,22; John D. Potter, PhD^34,35,36; Wei Zheng, MD, PhD¹

Question

How are secular trends of tobacco smoking associated with mortality across countries or regions by birth cohorts in Asia?

Findings

This pooled meta-analysis of 1 002 258 participants in 20 prospective cohort studies shows that smoking-attributable mortality continued to increase among Asian men in successive birth cohorts, with the tobacco smoking epidemic worsening in the past few decades.

Meaning

Tobacco smoking will remain a significant public health problem in most Asian countries, stressing the need to implement and enhance comprehensive tobacco-control programs in Asia.

Abstract

Understanding birth cohort-specific tobacco smoking patterns and their association with total and cause-specific mortality is important for projecting future deaths due to tobacco smoking across Asian populations.

Objectives

To assess secular trends of tobacco smoking by countries or regions and birth cohorts and evaluate the consequent mortality in Asian populations.

Design, setting and participant

This pooled meta-analysis was based on individual participant data from 20 prospective cohort studies participating in the Asia Cohort Consortium.

Between September 1, 2017, and March 31, 2018, a total of 1 002 258 Asian individuals 35 years or older were analyzed using Cox proportional hazards regression analysis and random-effects meta-analysis.

The pooled results were presented for mainland China; Japan; Korea, Singapore, and Taiwan; and India.

Exposures

Tobacco use status, age at starting smoking, number of cigarettes smoked per day, and age at quitting smoking.

Main outcomes and measures

Country or region and birth cohort–specific mortality and the population attributable risk for deaths from all causes and from lung cancer.

Results

Of 1 002 258 participants (51.1% women and 48.9% men; mean [SD] age at baseline, 54.6 [10.4] years), 144 366 deaths (9158 deaths from lung cancer) were ascertained during a mean (SD) follow-up of 11.7 (5.3) years.

Smoking prevalence for men steadily increased in China and India, whereas it plateaued in Japan and Korea, Singapore, and Taiwan.

Among Asian male smokers, the mean age at starting smoking decreased in successive birth cohorts, while the mean number of cigarettes smoked per day increased. These changes were associated with an increasing relative risk of death in association with current smoking in successive birth cohorts of pre-1920, 1920s, and 1930 or later, with hazard ratios for all-cause mortality of 1.26 (95% CI, 1.17-1.37) for the pre-1920 birth cohort, 1.47 (95% CI, 1.35-1.61) for the 1920s birth cohort, and 1.70 (95% CI, 1.57-1.84) for the cohort born in 1930 or later.

The hazard ratios for lung cancer mortality were 3.38 (95% CI, 2.25-5.07) for the pre-1920 birth cohort, 4.74 (95% CI, 3.56-6.32) for the 1920s birth cohort, and 4.80 (95% CI, 3.71-6.19) for the cohort born in 1930 or later. Tobacco smoking accounted for 12.5% (95% CI, 8.4%-16.3%) of all-cause mortality in the pre-1920 birth cohort, 21.1% (95% CI, 17.3%-24.9%) of all-cause mortality in the 1920s birth cohort, and 29.3% (95% CI, 26.0%-32.3%) of all-cause mortality for the cohort born in 1930 or later.

Tobacco smoking among men accounted for 56.6% (95% CI, 44.7%-66.3%) of lung cancer mortality in the pre-1920 birth cohort, 66.6% (95% CI, 58.3%-73.5%) of lung cancer mortality in the 1920s birth cohort, and 68.4% (95% CI, 61.3%-74.4%) of lung cancer mortality for the cohort born in 1930 or later.

For women, tobacco smoking patterns and lung cancer mortality varied substantially by countries and regions.

Conclusions and relevance

In this study, mortality associated with tobacco smoking continued to increase among Asian men in recent birth cohorts, indicating that tobacco smoking will remain a major public health problem in most Asian countries in the coming decades. Implementing comprehensive tobacco-control programs is warranted to end the tobacco epidemic.

[link url="http://news.vumc.org/2019/04/18/asian-nations-in-early-tobacco-epidemic/"]Asian nations in early tobacco epidemic: study[/link]

[link url="https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2729479"]Tobacco Smoking and Mortality in AsiaA Pooled Meta-analysis[/link]