Nicotine takes much longer than previously thought to reach peak levels in the brains of cigarette smokers, says a new study by Duke University Medical Center researchers.

Previously it was thought by scientists that it takes only seven minutes for nicotine inhaled in a puff of cigarette smoke to be taken up by the brain, and that each puff produced a spike of nicotine.

For the first time, Duke's researchers using PET imaging demonstrated that cigarette smokers actually experience a steady rise of brain nicotine levels during the course of smoking a whole cigarette.

The findings could lead to more effective treatments for smoking addiction, said the researchers.

Jed Rose, director of the Duke Center for Nicotine and Smoking Cessation Research, said," Previously it was thought that the puff-by-puff spikes of nicotine reaching the brain explained why cigarettes are so much more addictive than other forms of nicotine delivery, like the patch or gum."

Rose further added," Our work now calls into question whether addiction has to do with the puff-by-puff delivery of nicotine. It may actually depend in part on the overall rate at which nicotine reaches and accumulates in the brain, as well as the unique habit and sensory cues associated with smoking."

But when the researchers compared 13 dependent smokers to 10 non-dependent smokers, they were surprised to find the dependent smokers had a slower rate of nicotine accumulation in the brain.

Rose said," This slower rate resulted from nicotine staying longer in the lungs of dependent smokers, which may be a result of the chronic effects of smoke on the lungs." (With Inputs from Agencies)