A new study confirms that it is never too late to stop smoking - and the earlier you give up, the longer you are likely to live.
Scientists found that current smokers aged 70 and over were three times more likely to die over a period of six years than people who never smoked.
Quitting at different points in time between the ages of 30 and 69 progressively reduced the chances of dying.
Just 12.1% of the "never-smokers" in the study group died, compared with 33.1% of current smokers.
Of the former smokers, 16.2%, 19.7%, 23.9%, and 27.9% of those who quit in their 30s, 40s, 50s and 60s, respectively, died.
The US researchers reviewed data on more than 160,000 men and women participating in the NIH-AARP study, a large American investigation into health and diet.
Lead scientist Dr Sarah Nash, from the National Cancer Institute (NIH) in Bethesda, US, said: "These data show that age at smoking initiation and cessation, both key components of smoking duration, are important predictors of mortality in US adults aged 70 years and older.
"In the NIH-AARP study population, younger age at initiation was associated with increased risk of mortality, highlighting the importance of youth and early-adult smoking on lifetime mortality risk, even among people who live to age 70 years.
"In addition, former smokers were at substantially reduced risk of mortality after age 70 years relative to current smokers, even those who quit in their 60s. These finding show that smoking cessation should be emphasised to all smokers, regardless of age."
Of the total study population, almost 16% died during an average follow-up period of 6.4 years.
Almost 56% were former smokers and 6% were current smokers. Men were less likely than women to be never-smokers, and tended to have started smoking younger.
Causes of smoking-related death included lung, bladder, bowel, liver, pancreatic and stomach cancers, heart disease, stroke, diabetes and respiratory conditions such as pneumonia and chronic obstructive pulmonary disease (COPD).
The findings are reported in the American Journal of Preventive Medicine.
Tobacco companies lose latest UK court battle over plain packaging rules
Meanwhile, tobacco giants have lost the latest round of their legal battle against the UK government's new plain-packaging rules.
In May, they suffered what anti-smoking campaigners described as a "crushing defeat" at the High Court.
The day before new regulations come into force, a judge in London had declared that they were "valid and lawful in all respects".
Mr Justice Green rejected a judicial review action brought against Health Secretary Jeremy Hunt.
Leading companies then took their case on to the Court of Appeal.
But today, three judges in London rejected their challenge against the High Court's decision.
A number of companies, including British American Tobacco, Imperial Tobacco and Japan Tobacco International, challenged the legality of the "standardised packaging" regulations.
They argued that the Standardised Packaging of Tobacco Products Regulations 2015 would destroy valuable property rights and render products indistinguishable from each other.
Dismissing the appeal, Lord Justice Lewison, Lord Justice Beatson and Sir Stephen Richards ruled that the Health Secretary had "lawfully exercised his powers".
Deborah Arnott, chief executive of health charity Ash, said: "This is a victory for public health and another crushing defeat for the tobacco industry.
"This ruling should also encourage other countries to press ahead with standardised packaging, now that the industry's arguments have yet again been shown to be without foundation."
Ireland aims to have similar packaging rules in place in 2017.
