New Delhi, Oct. 26: People who stop smoking before the age of 40 may on average gain an extra 10 years of life expectancy, according to a study that researchers say has relevance to India where people typically quit only after falling ill.
A British study described as the world’s largest to assess the hazards of smoking and the benefits of quitting has shown that quitting before 40 can help avoid excess mortality observed among people who continue to smoke.
The study which tracked more than 11.8 lakh women has shown that the mortality risks in smokers increase steeply with the number of cigarettes smoked per day — and only eight cigarettes a day appears to double the excess risk of death compared to non-smokers.
The findings of the study will appear on Saturday in The Lancet, a medical journal. While the study is based exclusively on a large population of women, researchers say the results have implications for both men and women because the hazards of smoking are gender-neutral — the same for both men and women.
“Our results have relevance to India where smoking cessation rates are very low — almost no one stops smoking in India,” Richard Peto, professor of epidemiology at the University of Oxford and lead author of the study told The Telegraph.
An independent study led by a Canada-based Indian-origin researcher Prabhat Jha had shown four years ago that only 2 per cent of adults have quit smoking in India, and often after they had fallen sick. In contrast, Peto said, two-thirds of smokers have quit in the UK.
Many studies have earlier quantified the mortality risks associated with smoking, but the new British study is being described as the first to observe the “full eventual hazards or smoking” and the “full benefits of cessation” among women.
The full hazards and benefits “can be seen only as the generation born in the 1940s in the UK or the US is followed into the 21st century,” said Kirstin Pirie, a study team member at the University of Oxford. The study examined the health of women born in the 1940s some of whom were among the first generation in which women began to smoke substantial numbers of cigarettes in early adult life.
Among the 11.8 lakh women in the study, 20 per cent were smokers, 28 per cent were former smokers, and 52 per cent had never smoked. “Even women who smoked fewer than 10 cigarettes a day had double the overall mortality rate of non-smokers,” said Pirie.
The excess mortality among smokers was mainly from diseases such as lung cancer, chronic lung disease, heart disease, stroke and other respiratory illnesses known to be influenced by smoking, the researchers wrote in their paper.
Women who had stopped smoking in their late-20s or early-30s, decades later, still had “measurably higher” lung cancer mortality than did non-smokers, but by quitting they appeared to avoid about 97 per cent of the excess overall mortality. And women who quit while in their mid-40s or early-50s had substantially higher residual risk of lung cancer, but they too avoided 90 per cent excess risk of overall mortality compared to those who didn’t quit.
Peto says the findings have lessons for India which has high rates of smoking-related deaths among middle-aged people. “If Indian men and women stop smoking before 40, and preferably well before 40, then they will gain an extra 10 years of life expectancy,” Peto said in a statement. “Stopping earlier is even better,” he said.
Peto had co-authored and collaborated in a 2008 study that showed that India would have a million deaths each year from smoking-related causes each year during the 2010s. About 7 lakh of these deaths are among people between 30 and 60 years of age.
“We just don’t have enough numbers of people who’ve quit in India,” said Peto. “It would be a good day when we’re able to study the benefits of cessation of smoking in India.”
Medical epidemiologists say the long-term hazards of smoking in men have already been demonstrated. In most countries, men began to smoke long before women, which is why the long-term hazard of smoking and the benefits of quitting become apparent first in men then in women.