How far away from 45 are you? If you are a smoker, the answer to that question could mean the difference between life and death.

A study of hundreds of thousands of people in NSW has for the first time definitively answered the question of just how much damage smoking is doing to our health, with the data revealing it is likely to kill two-thirds of regular smokers - even higher than previously thought. That means 1.8 million Australian smokers are currently living with an axe over their head.

"Some kind of click": Steve Taylor, 23, recently gave up smoking. Credit:James Brickwood

The study has led public health experts to call for urgent re-investment in Australia's anti-smoking programs, and a ban on all tobacco company lobbying and PR.

But there is light at the end of the tunnel for smokers - it appears that as long as they quit before they turn 45 they have a good chance of recovering from much of the damage tobacco is doing to their bodies.