Smoking causes nearly 56 percent of lung cancer in men, a medical team in Seoul said in its report on Thursday.

The study which observed about 14,600 males in Seoul for the last 16 years also revealed that smoking increased the risk of lung cancer by fourfold in comparison to those who didn’t smoke at all.

Based on the percentage of male smokers in the Korean population, which is 41 percent, the team estimated that smoking may have caused 55.6 percent of lung cancer cases in men.

“These results highlight the need for an intervention program for quitting smoking in Korea,” said Seoul National University Medical School professor Ahn Yoon-ok who led the study.

Interestingly, the study showed that the prevalence of lung cancer in Korean smokers has remained unchanged, regardless of the number of observation years. The lung cancer risk in male smokers showed a similar fourfold increase, compared to lifelong non-smokers, in follow-up studies conducted for eight years and 16 years.

The team compared its study with a 50-year follow-up study of smoking and lung cancer in Britain that showed a 25-fold increase in lung cancer risk in men, compared to non-smokers.

Results from both studies differ due to differences in observation period but also because lung cancer risk is higher in non-smokers in Korea than those in the United Kingdom, the team said.

“This supports the idea that non-smokers in Korea suffer greatly from second-hand smoke. Korea needs to launch a systematic long-term study of smoking and lung cancer like Britain to investigate this,” said Bae Jong-myeon, professor at Jeju University Medical School.

South Korea’s smoking rate ranked second among 35 OECD-member countries in 2009.

A separate study showed that 1 in 4 smokers in Korea is a heavy smoker, defined as someone who smokes at least 15 cigarettes a day and who feels no need to quit smoking.

According to the Ministry of Health and Welfare, chances of becoming a heavy smoker were high among those who started to smoke before they reached 19, those who consume alcohol more often and those who were not exposed to any anti-smoking programs.

In a survey of 1,241 smokers conducted in 2010, 25.5 percent of respondents said they smoke at least 15 cigarettes a day. They answered that they have not tried to quit smoking in the last 12 months and have no intention to stop smoking in next six months.

Among those who belonged to the heavy-smoker category, 41.6 percent said they started to smoke when they were 19 or younger. The average starting age was 19.8 for heavy-smokers, while other respondents who smoke less said they started to smoke at 21.1 on average.

In a related move, the World Health Organization called for countries to ban all forms of tobacco advertising, promotion and sponsorship to help reduce the number of tobacco users, particularly young people.

One-third of young people’s experimenting with tobacco happens “as a result of exposure to tobacco advertising, promotion and sponsorship,” the WHO said in a statement published Thursday on its website. May 31 has been named “No Tobacco Day” by the United Nations’ health arm.

About 78 percent of teenagers aged 13-15 years are regularly exposed to some form of tobacco promotion worldwide, it added.

“Tobacco use ranks right at the very top of the list of universal threats to health, yet is entirely preventable,” WHO Director-General Margaret Chan said in the statement. “Governments must make it their top priority to stop the tobacco industry’s shameless manipulation of young people and women, in particular, to recruit the next generation of nicotine addicts,” she added.

By Cho Chung-un (christory@heraldcorp.com)