US scientists have developed a strategy to reduce smokers' nicotine dependence while continuing smoking.

In the study, funded by the US National Cancer Institute, 20 healthy adult smokers smoked their usual brand for a week and then followed six weeks of smoking cigarettes with progressively decreased nicotine content. One fourth of the smokers quit smoking completely while the study was in progress.

At the end of this period, the rest were free to return to their usual commercial cigarette brand, and most of them did. When tested one month later, they were smoking about 40 per cent fewer cigarettes a day, with a comparable reduction in nicotine intake.

Health experts have been concerned that reducing the nicotine content of cigarettes would lead to smoking more cigarettes, but the new research on reduced-nicotine content cigarettes strongly counters that premise.

Scientists say cigarettes marketed as ‘low-nicotine' do not work because they have high nicotine content and are "engineered" - made with highly porous paper and have ventilation holes above the filter - to deliver more nicotine when the smoker takes more frequent and bigger puffs.

The research was carried out by scientists at University College of San Francisco and San Francisco General Hospital Medical Center and was reported in the November 14 issue of the journal Cancer Epidemiology, Biomarkers and Prevention.

"Legislation giving the US's Food and Drug Administration the power to regulate tobacco products is being considered. This would empower the FDA to develop and enforce standards to make cigarettes less harmful - including the reduction of the nicotine yields," said study author Dr Neal Benowitz.