An effective prescription drug used to help people quit smoking initially helps women more than men, new research suggests.
The study, from Yale School of Medicine, found that Chantix (varenicline) helped women more than men for the first year of treatment. After a year, however, the anti-smoking medication worked equally well for both men and women.
Longer, healthier lives
"Studies show that women have a harder time quitting smoking than men, even as quitting has shown greater benefits to women's cardiovascular and respiratory health," Sherry McKee, professor of psychiatry and lead researcher of Yale's Specialised Centre of Research, said in a university news release.
Read: 12 tips for cutting down on cigarettes
"With this first comprehensive analysis of sex differences in the effectiveness of this drug, now women and their health care providers can better decide how to successfully quit and live longer, healthier lives," she added.
In the study, McKee's team looked at clinical trial data on more than 6,700 people who used Chantix to try and quit smoking.
The study found that, not adjusting for other factors, Chantix produced similar rates of smoking cessation for men and women a 53 percent quit rate after three months, the researchers said.
The trials were placebo-controlled, however, meaning that some people thought they were taking Chantix but were only taking a "dummy" placebo. According to the researchers, that's important, because many studies suggest that women are less likely than men to quit while taking a placebo, thus skewing the study results.
So, after taking this weaker placebo effect for women into account, McKee's team adjusted the data and found that Chantix was 46 percent more effective in boosting the odds of quitting for women versus men after three months of treatment.
Read: Quitting smoking may boost diabetes risk in older women
And after six months, the drug was still 31 percent more effective at maintaining complete abstinence among women than men, the researchers found.
"While it's clear that sex differences in Chantix efficacy exist, we don't yet know why varenicline is particularly effective for women," McKee said.
It's possible that sex differences in the brain's nicotine receptor system could help explain why Chantix is initially more effective for women, the researchers reasoned.
According to the U.S. Centres for Disease Control and Prevention, cigarette smoking kills more than 480,000 Americans each year, making it the leading preventable cause of sickness and death in the United States.
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Image: Chantix, the anti-tabacco drug from iStock
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