For anyone who thinks that the “I only smoke when I drink” strategy will help them avoid the pitfalls of their pack-a-day friends, we have some bad news. According to new research, heavy cigarette smokers who quit actually have a lower risk of developing smoking-related diseases than those who are light smokers over a longer period of time — even if heavy smokers happen to have smoked more cigarettes overall.

The findings, presented Tuesday at the American Thoracic Society International Conference in San Diego, come from data gathered in the Coronary Artery Risk Development in Young Adults (CARDIA) study, in which 3,140 participants had their lung function measured intermittently over 30 years.

Study participants enrolled in four different cities: Birmingham, Chicago, Minneapolis, and Oakland. At the start of the study, the average participant age was 25 and nearly half were African American. About 57 percent were female. At the beginning of the study, about half of the participants “endorsed lifetime smoking.”

Comparing Lung Functions

Data attained from spirometry and chest CT scans at the beginning of the study, as well as two, five, 10, 20, and 30 years after enrolling, allowed researchers to observe how different levels of smoking affect lung health, said lead author Amanda Mathew, PhD, research assistant professor at Northwestern University Feinberg School of Medicine.

“Participants were asked about their smoking each year, which minimized recall bias and allowed us to model changes in smoking habits over time,” she said.

Predictably, stable, heavy smokers experienced the largest decline in lung function. Compared to non smokers, heavy smokers were nearly eight times at risk of obstructive lung disease and more than twenty times more likely to get emphysema.

What They Found

But the study’s findings about low-rate smokers are what really stand out. It appears that heavy smokers that quit showed less decline in air capacity in the lungs — measured as FEV1 — than stable, low rate smokers, as well as lower odds of emphysema. This was despite them having on average smoked more cigarettes at year 25 in the study than low-rate smokers. Low-rate smokers were defined as those who smoked less than 10 cigarettes a day, on average.

“Smoking duration was a better predictor of emphysema risk than smoking intensity, demonstrating the detrimental health effects of long-term smoking regardless of smoking amount,” the study notes.

The study speaks to the importance of quitting cold turkey. With enough time behind them, former heavy smokers appear to be better of than those who still choose to light up, if only a few times a day.

“There is no safe threshold of smoking on lung health,” Matthew says. “Cutting down can be a great first step, but quitting for good is the most effective way to reduce lung disease risk.”