Alarge U.S. study has found that the mortality rate of a person who quits smoking before age 35 was on par with "never smokers."

The study, published Monday in the journal JAMA Network Open, used data from the U.S. National Health Interview Survey and the National Death Index.

"Among men and women from diverse racial and ethnic groups, current smoking was associated with at least twice the all-cause mortality rate of never smoking," the study authors wrote in the paper.

"Quitting smoking, particularly at younger ages, was associated with substantial reductions in the relative excess mortality associated with continued smoking," the authors further stated.

However, those who quit smoking at a later age showed their mortality rate decline.

The study found people, who gave up smoking between ages 35 and 44, had a 21% higher death rate from any cause than never smokers. A 47% higher all-cause mortality rate than never-smokers was observed in those who quit between ages 45 and 54.

Never smokers are those people who have smoked less than 100 cigarettes in their life.

This is the third such study to find that age 35 is the appropriate age to quit smoking, John P. Pierce, a professor emeritus in the Department of Family Medicine and Public Health at the University of California, San Diego, and who was not involved in the study, wrote in a commentary of the study.

"It has been known for a long time that the earlier a smoker quits, the better," Pierce wrote. "However, it is now possible to be more specific with respect to the age that a smoker quits."

The survey data had more than 550,000 adult participants, between 25 and 84 years old, who filled out the questionnaires between January 1997 and December 2018.

The lot included current smokers, former smokers, and never-smokers.

From the data from the National Death Index, the researchers found nearly 75,000 of the study subjects had died by the end of 2019.

The group with the worst outcome, the study found, was non-Hispanic white smokers, who had the highest all-cause mortality rate -- about three times higher compared to never smokers.

On the other hand, non-white smokers, both Hispanic and non-Hispanic people, showed slightly lower mortality rates, which were about double that of never smokers.

The lower mortality rate accorded to this group might be due to fewer cigarettes smoked per day, on average. They also start smoking at older ages and are less likely to smoke daily, compared with white subjects.

"These results remind us that reducing smoking intensity (cigarettes per day) should be one of the goals for tobacco control programs," Pierce commented.

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