Women who quit smoking by the age of 30 will almost completely avoid the risks of dying early from tobacco-related diseases, according to a study of more than a million women in the UK.
The results, published in the Lancet, showed lifelong smokers died a decade earlier than those who never started.
But those who stopped by 30 lost, on average, a month of life and if they stopped by 40 they died a year younger.
Health experts said this was not a licence for the young to smoke.
The study followed the first generation of women to start smoking during the 1950s and 60s. As women started smoking on a large scale much later than men, the impact of a lifetime of cigarettes has only just been analyzed for women.
“What we’ve shown is that if women smoke like men, they die like men,” said lead researcher Prof. Sir Richard Peto, from Oxford University.
Women who quit smoking by the age of 30 will almost completely avoid the risks of dying early from tobacco-related diseases
He said: “More than half of women who smoke and keep on smoking will get killed by tobacco.
“Stopping works, amazingly well actually. Smoking kills, stopping works and the earlier you stop the better.”
The records from 1.2 million women showed that even those who smoked fewer than 10 cigarettes a day were more likely to die sooner.
Sir Richard Peto said that it was exactly the same picture as for men.
The British Lung Foundation said the prospects for long-term health were much better if people stopped smoking before they were 30, but cautioned that this was not a licence to smoke “as much as you want in your 20s”.
Its chief executive, Dr. Penny Woods, said: “Stopping smoking can also be difficult to do – an estimated 70% of current smokers say they want to quit, so you shouldn’t start and just assume you’ll be able to quit smoking whenever you want to.
“The best thing for your health is to avoid smoking at all.”
Prof. Robert West, from the health behaviour research unit at University College London, said it was important to remember that smoking had more effects on the body than leading to an early death, such as ageing the skin.
“Around your mid-20s your lung function peaks and then declines. For most people that’s fine – by the time you’re into your 60s and 70s it’s still good enough. But if you’ve smoked, and then stopped there is irreversible damage, which combined with age-related decline can significantly affect their quality of life.
“Obviously there is an issue around smoking if they want to get pregnant because it affects fertility and then there are the dangers of smoking during and after pregnancy.”
People dangerously underestimate the health risks linked to smoking cannabis due to lack of awareness, experts have warned.
The British Lung Foundation (BLF) carried out a survey of 1,000 adults and found a third wrongly believed cannabis did not harm health.
And 88% incorrectly thought tobacco cigarettes were more harmful than cannabis ones – when the risk of lung cancer is actually 20 times higher.
The BLF said the lack of awareness was “alarming”.
Latest figures show that 30% of 16-59 year-olds in England and Wales have used cannabis in their lifetimes.
People dangerously underestimate the health risks linked to smoking cannabis due to lack of awareness
A new report from the BLF says there are established scientific links between smoking cannabis and tuberculosis, acute bronchitis and lung cancer.
Cannabis has also been shown to increase chances of developing mental health problems such as schizophrenia.
Part of the reason for this, say the experts, is that people smoking cannabis take deeper puffs and hold them for longer than when smoking tobacco cigarettes.
This means that someone smoking a cannabis cigarette inhales four times as much tar as from a tobacco cigarette, and five times as much carbon monoxide, the BLF says.
Its survey found that young people are particularly unaware of the risks.
Almost 40% of the under-35s surveyed – the age group most likely to have smoked it – thought cannabis was not harmful.
However, each cannabis cigarette they smoke increases their chances of developing lung cancer by as much as an entire packet of 20 tobacco cigarettes, the BLF warned.
BLF chief executive, Dame Helena Shovelton, said: “It is alarming that, while new research continues to reveal the multiple health consequences of smoking cannabis, there is still a dangerous lack of public awareness of quite how harmful this drug can be.
“This is not a niche problem – cannabis is one of the most widely-used recreational drugs in the UK, with almost a third of the population having tried it.
“We therefore need a serious public health campaign – of the kind that has helped raise awareness of the dangers of eating fatty foods or smoking tobacco – to finally dispel the myth that smoking cannabis is somehow a safe pastime.”
The BLF’s report says there should be a public education programme to raise awareness of the impact of smoking cannabis and increased investment in research into the health consequences of its use.