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Title: Emerging tobacco hazards in China

Authors: Niu S, Yang G, Chen Z, Wang J, Wang G, He X, et al.

Reference: British Medical Journal. 1998; 317:1423-1424.

Reviewer: Joaquin Barnoya 

Problem addressed: The recent substantial increase in cigarette consumption by Chinese men will eventually cause a substantial increase in mortality.

Purpose of study: To monitor the long term evolution of the increase in tobacco-related mortality

Study design: Representative, prospective

Methods: In 1987, the Chinese Academy of Preventive Medicine interviewed 224,500 men more than 40 years old on smoking, drinking and medical history (80% of a representative population). Of those interviewed, 30% were urban (the same proportion as in China as a whole). Mortality was prospectively monitored through medical records. By January 1996, only 2% were untraced and 6% had died, with neoplastic, respiratory, vascular and other causes equally common.

Results: By 1990, 73% smoked (68% urban and 75% rural); 1% were former smokers (Many having stopped because they were ill); of the smokers, 55% used only cigarettes and 30% had begun before the age of 20.  At the end of 5 year follow up the overall mortality of smokers was significantly higher than that of never smokers. Relative risk was 1.19 (95% CI 1.13-1.25 P < .00001) and was highest among men who had begun smoking before age 20.  The excess mortality chiefly involved neoplastics (RR 1.26; 95% CI 1.13-1.55 p< 0.0001), respiratory (RR 1.38; 95% CI 1.25-1.55 p< 0.0001), and vascular (RR 1.13; 95% CI 1.07-1.20 p<0.01).  If these associations with smoking are largely causal, then tobacco causes 12% of all male adult deaths.

Discussion: This prospective study is consistent with smaller prospective studies and with retrospective studies in showing that smoking is already an important cause of death in China, involving mainly neoplastic, respiratory and vascular disease. By 1990 smoking was already casing 12% of Chinese adult male deaths, that would corresponds to 0.7 million male tobacco related deaths for the year 2000. This health effect reflects the consequences of past smoking patterns, the future health effects of current smoking patterns will be much larger.

By now, in China the all cause mortality ratio for smokers starting before the age 20 is already 1.34, indicating that even at the current death rates about 1 smoker in 4 would be killed by tobacco. This risk shows that in the past Chinese men may not have smoked persistently. In urban areas the risk ratio for those who began before age 20 the risk ratio is already approaching 2, suggesting that about half will be killed by tobacco.

As the main increase in cigarette consumption in China took place recently (mean cigarette consumption 1 in 1952 to 10 in 1992), at these smoking patterns Chinese tobacco mortality will increase substantially. Of all male deaths at ages 35-69 the proportion attributed to tobacco will rise from 12% in 1990 to about 33% in 2030 because in both urban and rural areas two thirds of young men become cigarettes smokers and cessation is rare. This epidemic will be monitored by the long term continuation of this study. Reviewers Comments

-It is interesting that the incidence of deaths due to respiratory disease is virtually the same as vascular diseases in the population studied. As other cardiovascular risk factors become more prevalent, the detrimental effect of tobacco on cardiovascular health will be compounded.

-The alarming rate of cigarette consumption reported in this prospective study is above the peak consumption seen in the United States in the past. We can only hope that China has reached its peak consumption and that coordinated efforts will address this public health problem with support of the legal, social and scientific community.

-As primordial prevention is enhanced to control the scrooge of tobacco use in China and other unhealthy lifestyles, health services development should be aimed to deal with the burden of tobacco related diseases foreseen for the future.