Once enslaved by cigarettes, actress Pam Oei broke free and is now smoke-free - even refusing roles that require her to puff away.

"I refuse to smoke in a role," said Ms Oei, 37, well-known for being one third of the comedy cabaret act Dim Sum Dollies.

The actress, who is married with no kids and who quit smoking in 2006, has this to say about smoking onscreen or onstage: "It often adds nothing to the character but makes smoking look normal or glamorous.

"If you watch Fight Club, Brad Pitt looks hot and he smokes a lot. It gives the impression that you can smoke too and look just as good."

A smoking cessation therapist as well, Ms Oei wants to dispel such a depiction.

She started smoking when she was 17. She said: "I hung out with some boys who played the guitar and we jammed a lot. All of them smoked.

"After my first puff, I didn't like it but I persevered."

Her story is typical of many young people who start lighting up.

Dr Kenneth Chan, a consultant at the department of respiratory and critical care medicine at Singapore General Hospital, said: "Most people in Singapore start smoking in their adolescent years. Common reasons include peer pressure or having friends who smoke, curiosity, boredom and the desire to relieve stress."

He added: "Having a parent who smokes increases the risk of the child picking up smoking substantially."

The Health Promotion Board's National Health Surveillance Study 2007 found that smoking every day was most prevalent among people between 18 and 29 years of age.

It also found that the proportion of men and women in this age group who smoked had increased, from 18.2 per cent and 6.6 per cent in 2004 respectively, to 25.4 per cent and 9.1 per cent in 2007.

The villain of the piece is nicotine.

The nicotine in the inhaled tobacco smoke goes from the lungs to the bloodstream and then the brain - within seven to 10 seconds.

Dr Chan said once nicotine gets into the brain, it attacks the central nervous system by mimicking a naturally occurring chemical called acetylcholine.

As a result, nerve cells in the front of the brain unwittingly release the neurotransmitter dopamine, which is responsible for feelings of pleasure and well-being.

Mr Eddy Lim, a senior pharmacist at the National University Hospital, said: "Nicotine activates the same reward pathways in the brain, like other abusive drugs, although to a lesser degree.

"While nicotine increases the level of dopamine in the brain, the effects wear off within minutes, so smokers must continue dosing themselves throughout the day to maintain the pleasurable effects of nicotine and to prevent withdrawal symptoms."

There is more bad news if you are a smoker. Nicotine also triggers the release of adrenaline, which causes the heart rate and blood pressure to shoot up.

Mr Lim said: "The smoker then experiences rapid, shallow breathing and finds his heartbeat racing."

Nicotine also inhibits the release of insulin, a hormone responsible for removing excess sugar from a person's blood. A smoker thus has a higher blood sugar content and his appetite is suppressed.

Ms Tan Cin Yee, a senior pharmacist at Tan Tock Seng Hospital, said: "Over time, tolerance to smoking's stimulating effect develops and the smoker needs to puff more to get the same effect."

In a spiral, increasing tolerance and nicotine's efficiency at hijacking the brain's reward pathways egg smokers to keep on puffing away.

On why many smokers continue to light up, a Health Promotion Board spokesman referred to a "triangle of addiction".

He said: "Smokers experience physical addiction because of the nicotine acting on their brains.

"They may also suffer from psychological or emotional dependence where they perceive that cigarettes make them feel better or form a habitual dependence as smoking has become a routine in their lives."

junec@sph.com.sg

This article was first published in Mind Your Body, The Straits Times.