Even occasional smoking—as few as six to 10 cigarettes per month—is associated with a higher risk of death than never having smoked, Healio reports.

This finding from a new study published in JAMA Network Open, the paper’s authors stress, points to the importance of quitting smoking entirely, not just cutting back. While reducing smoking to below a pack a day is indeed associated with a lower risk of death, only full cessation of cigarette use is likely to mitigate smokers’ smoking-driven excess risk of death over the years until it hits a level nearly comparable to that of those who have never smoked.

The study authors analyzed data from the National Institutes of Health Tobacco Use Supplement to the Current Population Survey, which was conducted during multiple years between 1992 and 2011. They tied these data to responses from participants in the National Longitudinal Mortality Survey.

All told, the research cohort included 505,500 people, including smokers and nonsmokers, between ages 18 and 103. Among them, 47,000 people died.

The daily smokers in the cohort smoked a median of 600 cigarettes monthly, while nondaily smokers who had cut down from smoking daily had a median of 75 cigarettes each month, and those who had always smoked nondaily smoked a median of 40 cigarettes per month.

Compared with people who had never smoked, those who currently smoked daily were 2.32 times more likely to die of any cause, and those who were lifelong nondaily smokers were 1.82 times more likely to die. This finding held despite the 15-fold difference in the monthly number of cigarettes between the two groups.

All it took was six to 10 cigarettes per day for the researchers to detect an increase in the overall risk of death among the nondaily smoking cohort members compared with never smokers. The more cigarettes people smoked, the greater the excess death risk, they found.

The risk of death was lower among those who reduced from smoking daily to doing so nondaily, compared with the death rate among their counterparts who were still smoking daily.

Additionally, 10 years after daily smokers switched to nondaily use of cigarettes, their risk of death declined such that, at a 1.73-fold increased risk of death compared with never smokers, their excess risk of death was on par with that of lifelong nondaily smokers.

That said, those who went from smoking daily to not at all had only a 1.18-fold increased risk of death compared with never smokers 10 years after downshifting their cigarette habit.

Smoking at any level was associated with an especially large increase in the risk of various smoking-related cancers. In particular, the risk of lung cancer was 5.64-fold higher in lifelong nondaily smokers, 10.22-fold higher in people who went from smoking daily to nondaily smoking and 13.96-fold higher in daily smokers, compared with nonsmokers.

“Although reducing smoking from daily to nondaily was associated with decreased mortality risk, cessation was associated with far greater benefit,” the study authors concluded. “Lifelong nondaily smokers have higher mortality risks than never smokers, even among those smoking six to 10 cigarettes per month. Thus, all smokers should quit, regardless of how infrequently they smoke.”

To read the Healio article, click here.

To read the study, click here.