Cigarette smokers die on average 10 years earlier than non-smokers but kicking the habit, even at 50 years old, can halve the risk, according to half a century of research reported on June 22, 2004. Findings from a 50-year study into the dangers of smoking showed that if people quit by the age of 30 they can avoid nearly all of the risk of dying prematurely. A smoker is shown in London on the 'World No Tobacco Day', May 31. Photo by David Bebber/Reuters

词汇：

average adj.一般的，通常的，平均的

halve vt.平分，减半

prematurely adv.过早地，早熟地

'World No Tobacco Day' 世界无烟日