NEW YORK - Lighting up could be slowing you down in the bedroom.

A US study suggests that men who successfully stopped smoking improved on lab measurements of sexual health more than those who relapsed after a quit-smoking program, showing that smoking may be affecting the sexual health of men who consider themselves perfectly all right in bed, researchers said.

"With younger men, the risks of smoking in that population appear more far off. They think, 'I don't really need to worry about this until much farther down the road," said study author Christopher Harte, from the VA Boston Healthcare System, who published findings in the British Journal of Urology International.

"Regardless of if this really does apply to all men who smoke or not (the goal was) just getting the word out that men could be aware of this finding, so it could influence their decisions to start the quitting process," he told Reuters Health, though he did say the study was still not definitive.

Harte and co-author Cindy Meston from the University of Texas at Austin enrolled 65 men without self-reported impotence in an eight-week quit smoking program using nicotine patches. Before treatment, halfway through and a few weeks after, they brought the men into a locked lab and showed them a racy film.

While they watched, men kept track of how aroused they were and a device measured how much their penis grew or shrank. Separately, they also filled out surveys about their sexual function outside of the lab, including questions about desire and sexual satisfaction.

By the end of the study, there were 20 men that hadn't lit up in at least a week, while 45 men were still smoking.

Quitters saw a greater increase in penile growth, measured by width and not length, compared to non-quitters. By their own scoring, those men also reached their peak level of arousal sooner than men who were still lighting up.

However, men who had dropped the habit didn't report any sexual improvement in "real-life" settings, the researchers said. It's also possible that the improvements they saw in the lab may take time to translate to the bedroom.

"It might take longer for men to actually notice their level of difference subjectively outside of the lab, which is also dependent on their relationship with their sexual partner," Harte said.

While smoking has been linked to a host of other health problems such as cancer and heart disease, the researchers said their finding is a new angle for doctors to use with men who are still reluctant to try quitting.

Previous research has shown that long-term smokers are up to twice as likely to have impotence as non-smokers. Smoking can show blood vessel dilation, which is necessary to get an erection, said Lydia Bazzano, who has studied erectile dysfunction at the Tulane University Health Sciences Center.

Harte said the point of the study may be that the connection doesn't just apply to men with severe erectile dysfunction issues.

"The take-home point is that even men who don't have a clinical diagnosis of (erectile dysfunction) ... may still benefit from quitting smoking," he added.