If the trend is mirrored in China, half of an estimated 200 million men who smoke could die from tobacco-related diseases in the next three decades.

BBC: China's smoking timebomb

However, those who gave up by the age of 30 almost completely avoided the risks of dying early from tobacco-related diseases with those stopping by 40 died a year younger.

BBC: Female smoking death risk 'has soared'

According to research in more than one million women, those who give up smoking by the age of 30 will almost completely avoid the risks of dying early from tobacco-related diseases.

BBC: Smoking 'poses bigger risk to women'