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Review
. 2015 Oct 10;386(10002):1447-56.
doi: 10.1016/S0140-6736(15)00340-2.

Contrasting Male and Female Trends in Tobacco-Attributed Mortality in China: Evidence From Successive Nationwide Prospective Cohort Studies

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Review

Contrasting Male and Female Trends in Tobacco-Attributed Mortality in China: Evidence From Successive Nationwide Prospective Cohort Studies

Zhengming Chen et al. Lancet. .
Free PMC article

Abstract

Background: Chinese men now smoke more than a third of the world's cigarettes, following a large increase in urban then rural usage. Conversely, Chinese women now smoke far less than in previous generations. We assess the oppositely changing effects of tobacco on male and female mortality.

Methods: Two nationwide prospective studies 15 years apart recruited 220,000 men in about 1991 at ages 40-79 years (first study) and 210,000 men and 300,000 women in about 2006 at ages 35-74 years (second study), with follow-up during 1991-99 (mid-year 1995) and 2006-14 (mid-year 2010), respectively. Cox regression yielded sex-specific adjusted mortality rate ratios (RRs) comparing smokers (including any who had stopped because of illness, but not the other ex-smokers, who are described as having stopped by choice) versus never-smokers.

Findings: Two-thirds of the men smoked; there was little dependence of male smoking prevalence on age, but many smokers had not smoked cigarettes throughout adult life. Comparing men born before and since 1950, in the older generation, the age at which smoking had started was later and, particularly in rural areas, lifelong exclusive cigarette use was less common than in the younger generation. Comparing male mortality RRs in the first study (mid-year 1995) versus those in the second study (mid-year 2010), the proportional excess risk among smokers (RR-1) approximately doubled over this 15-year period (urban: RR 1·32 [95% CI 1·24-1·41] vs 1·65 [1·53-1·79]; rural: RR 1·13 [1·09-1·17] vs 1·22 [1·16-1·29]), as did the smoking-attributed fraction of deaths at ages 40-79 years (urban: 17% vs 26%; rural: 9% vs 14%). In the second study, urban male smokers who had started before age 20 years (which is now typical among both urban and rural young men) had twice the never-smoker mortality rate (RR 1·98, 1·79-2·19, approaching Western RRs), with substantial excess mortality from chronic obstructive pulmonary disease (COPD RR 9·09, 5·11-16·15), lung cancer (RR 3·78, 2·78-5·14), and ischaemic stroke or ischaemic heart disease (combined RR 2·03, 1·66-2·47). Ex-smokers who had stopped by choice (only 3% of ever-smokers in 1991, but 9% in 2006) had little smoking-attributed risk more than 10 years after stopping. Among Chinese women, however, there has been a tenfold intergenerational reduction in smoking uptake rates. In the second study, among women born in the 1930s, 1940s, 1950s, and since 1960 the proportions who had smoked were, respectively, 10%, 5%, 2%, and 1% (3097/30,943, 3265/62,246, 2339/97,344, and 1068/111,933). The smoker versus non-smoker RR of 1·51 (1·40-1·63) for all female mortality at ages 40-79 years accounted for 5%, 3%, 1%, and <1%, respectively, of all the female deaths in these four successive birth cohorts. In 2010, smoking caused about 1 million (840,000 male, 130,000 female) deaths in China.

Interpretation: Smoking will cause about 20% of all adult male deaths in China during the 2010s. The tobacco-attributed proportion is increasing in men, but low, and decreasing, in women. Although overall adult mortality rates are falling, as the adult population of China grows and the proportion of male deaths due to smoking increases, the annual number of deaths in China that are caused by tobacco will rise from about 1 million in 2010 to 2 million in 2030 and 3 million in 2050, unless there is widespread cessation.

Funding: Wellcome Trust, MRC, BHF, CR-UK, Kadoorie Charitable Foundation, Chinese MoST and NSFC.

Figures

Figure 1
Figure 1
Chinese female smoking uptake rate by year of birth and locality 300 000 women seen in ten study areas in about 2006, with birth years grouped as: before 1935, 1935–44, 1945–54, 1955–64, and 1965 or later. The two areas where many older women smoked are in Harbin (urban northeast China) and Sichuan (rural southwest China). Taking all ten areas together, the prevalences of ever-smoking among women born in the 1930s, 1940s, 1950s, 1960s, and 1970s were, respectively, 10%, 5%, 2%, 1%, and <1% (3097/30 943, 3265/62 246, 2339/97 344, 926/94 772, and 142/17 161).
Figure 2
Figure 2
Urban and rural Chinese male smoking patterns, by year of birth—prevalence, consumption, age started, and tobacco type smoked initially 210 000 men seen in about 2006 (at the 2004–08 baseline survey for the second prospective study). Prevalence of smoking (A); amount smoked per day when last smoked (B); Mean age started smoking regularly (C); and percentage of all smokers who used cigarettes when first started (D). To avoid reverse causality biasing the apparent effects of smoking and of cessation, in panel (A) and in the main analyses, the few men who had stopped smoking because they were ill are combined with the continuing smokers, leaving the ex-smokers who had stopped by choice. The overall proportions of men who had stopped because they were ill were 2·16%, 2·47%, 2·19%, 1·08% and 0·12% for those born during the 1930s, 1940s, 1950s, 1960s, and 1970s respectively.
Figure 3
Figure 3
All-cause smoker versus never-smoker mortality rate ratio (RR) among urban and rural Chinese men in two prospective studies, by time period (about 1995 or about 2010) and by age started smoking regularly Each study followed about 200 000 men. Each group-specific CI (including that for never-smokers, given by the width of the shaded strip) reflects the variance of the log risk in that one group, so comparisons of RRs use variances from more than one group.
Figure 4
Figure 4
Ex-smoker versus never-smoker all-cause mortality rate ratio (RR), by years stopped smoking and reason stopped, for men in the second study Each group-specific CI (including that for never-smokers, given by the width of the shaded strip) reflects the variance of the log risk in that 1 group, so comparisons use variances from more than one group.

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