In China, smoking now causes nearly a quarter of all cancers in adult males. The finding comes from a large study published early online in CANCER, a peer-reviewed journal of the American Cancer Society, as part of a Special Issue on Lung Cancer in China. High uptake rates of cigarette smoking in teenaged males and continued use in adulthood foreshadow even greater tobacco-related cancer risks for the nation.
Tobacco-related deaths have been declining steadily in most developed countries; however, China now produces and consumes about 40 percent of the world's cigarettes, with much of the rapid increase taking place since the early 1980s, involving almost exclusively only men.
To get a sense of the current smoking-related cancer risks in China, a research team led jointly by Professor Zhengming Chen, DPhil, of the University of Oxford in the UK and Professor Liming Li, MD, of the Chinese Academy of Medical Sciences in China, analyzed data from a nationwide prospective study called the China Kadoorie Biobank, which recruited 210,259 men and 302,632 women aged 30 to 79 years from 10 areas of China from 2004 to 2008. The study recorded approximately 18,000 new cancers during seven years of follow-up.
Among the major findings:
* Sixty-eight percent of men in the study were smokers, and they had a 44 percent increased risk of developing cancer compared with nonsmokers.
* This excess risk accounted for 23 percent of all cancers that arose between the ages of 40 and 79 years, with significantly elevated risks of cancers of the lung, liver, stomach, esophagus, and a collection of five other minor sites.
* Among ex-smokers (6.7%) who had stopped by choice, there was little excess cancer risk within 15 years after quitting.
* In contrast to men, only three percent of females in the study were smokers, and they experienced a 42 percent increased risk of cancer compared with nonsmokers.
* Smoking causes an estimated 435,000 new cancers (360,000 in men and 75,000 in women) each year in China.
"The tobacco-related cancer risks among men are expected to increase substantially during the next few decades as a delayed effect of the recent rise in cigarette use, unless there is widespread cessation among adult smokers," the authors wrote. The study also noted that the first generation of men in China to experience the full extent of tobacco risks will probably be those who were born during the 1970s or 1980s, who reached adulthood when cigarette consumption was high. By contrast, this is the least exposure for the female generation in China. "If smoking rates remain low in women, tobacco may soon be responsible for most of the difference in life expectancy between men and women in China. Widespread smoking cessation offers China one of the most effective, and cost-effective, strategies for avoiding cancer and premature death over the next few decades" said Professor Zhengming Chen, the lead author and principal investigator of the China Kadoorie Biobank.
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