If quitting smoking is one of your New Year’s resolutions, you might want to consider cutting back on your drinking, too.

New research has found that heavy drinkers who are trying to stop smoking may find that reducing their alcohol use can also help them quit their daily smoking habit. Heavy drinkers’ nicotine metabolite ratio – a biomarker that indicates how quickly a person’s body metabolizes nicotine – reduced as they cut back on their drinking.

Past research has suggested that people with higher nicotine metabolism ratios are likely to smoke more and that people with higher rates have a harder time quitting. Slowing a person’s nicotine metabolism rate through reduced drinking could provide an edge when trying to stop smoking, which is known to be a difficult task, said Sarah Dermody, an assistant professor at Oregon State University and the study’s lead author.

“It takes a lot of determination to quit smoking, often several attempts,” Dermody said. “This research suggests that drinking is changing the nicotine metabolism as indexed by the nicotine metabolite ratio, and that daily smoking and heavy drinking may best be treated together.”

The study was just published in the journal Nicotine & Tobacco Research.

Dermody, who is based in in the School of Psychological Science in OSU’s College of Liberal Arts, studies risky behaviors such as alcohol and nicotine use with the goal of better understanding factors that contribute to alcohol and nicotine use and how best to intervene with problematic use of these substances.

Use of both alcohol and cigarettes is widespread, with nearly 1 in 5 adults using both. Cigarette use is especially prevalent in heavy drinkers. Drinking is a well-established risk factor for smoking, and smoking is well-established risk factor for drinking.

Dermody and colleagues at the Centre for Addiction and Mental Health in Toronto, Canada, wanted to better understand the links between the two. They studied the nicotine metabolite ratio, an index of nicotine metabolism, in a group of 22 daily smokers who were seeking treatment for alcohol use disorder – the medical term for severe problem drinking – over several weeks.

“What’s really interesting is that the nicotine metabolite ratio is clinically useful,” Dermody said. “People with a higher ratio have a harder time quitting smoking cold turkey. They have are also less likely to successfully quit using nicotine replacement therapy products.”

They found that as the men in the study group reduced their drinking – from an average of 29 drinks per week to 7 – their nicotine metabolite rate also dropped.

The researchers’ findings for men replicated those of an earlier study that found similar effects and provide further evidence of the value of the nicotine metabolite ratio biomarker to inform treatment for smokers trying to quit, Dermody said.

“The nicotine metabolite ratio was thought to be a stable index, but it may not be as stable as we thought,” Dermody said. “From a clinical standpoint, that’s a positive thing, because if someone wants to stop smoking, we may want to encourage them to reduce their drinking to encourage their smoking cessation plan.”

The women in the study did not see reductions in their nicotine metabolite ratio, but the researchers also did not find that the women in the study reduced their drinking significantly during the study period.

“The rate of drinking for women in the study started low and stayed low,” Dermody said. “I anticipate that in a larger generalized study we would not see the difference between men and women like that.”

Dermody is preparing a new study of the links between smoking and drinking. She hopes to recruit heavy drinkers who also smoke to participate in an intervention to reduce their drinking. The study will also examine the effects on smoking to try and replicate the findings in a larger group.

“This research is demonstrating the value in addressing both smoking and drinking together,” she said. “The question now is how best to do that.”