Even older smokers may reduce their risk of death and health complications from cardiovascular disease by quitting, a large international study suggests.

Researchers analyzed data on more than half a million people age 60 and older in 23 countries and found that compared with people who never used cigarettes, current smokers were more than twice as likely to die of cardiovascular causes. But for former smokers, the increased risk of death was only 37 percent.

“We were surprised how clearly and swiftly the risk decreased after quitting smoking,” lead study author Dr. Ute Mons, a scientist at the German Cancer Research Center in Heidelberg, said by email. “The risk reduction is quite comparable to that in younger populations, so the good news is there seems to be no age limit for health benefits from quitting smoking.”

Mons and colleagues reviewed records on smoking habits, as well as medical history and socioeconomic factors for 503,905 participants in previous research projects. The largest study included in their review had 366,919 participants in the U.S.

Among the approximately 475,000 people with records on their cigarette use, 40 percent never smoked, while about 47 percent had quit and 12 percent were current smokers. Overall, 44 percent of participants were women.

For current smokers, the risk of death increased with the amount of cigarette consumption, with the heaviest smokers 2.6 times more likely to die of cardiovascular causes than people who never smoked.

At the same time, smoking cessation lowered the risk of death. Participants who had quit less than five years beforehand had their risk drop by 10 percent. Quitting five to nine years before lowered the risk by 16 percent compared with current smokers. Stopping 10 to 19 years earlier cut risk by 22 percent, while more than 20 years of cessation decreased the risk by 39 percent.

Complications from smoking, including strokes, were also less likely to happen in former smokers than in current smokers, the study team reports in BMJ.

The authors also calculated another way of looking at the benefits of quitting. They found that being a current smoker meant cardiovascular problems would arise an average of six years sooner than for never-smokers. But quitting smoking rolled back that “risk advancement,” giving former smokers back an extra two to 2½ healthy years.

While doctors often advise patients that it’s never too late to quit smoking, previous research hasn’t proven that older smokers can reduce their risk of death from cardiovascular causes by quitting, said Bo Zhang, a scientist at the Ontario Tobacco Research Unit affiliated with the University of Toronto.

“This study definitely adds new evidence about the benefit of smoking cessation among older smokers,” Zhang, who wasn’t involved in the current study, said by email.

One shortcoming of the study, however, is that only a small proportion of participants were over the age of 70 and it’s unclear how many of the former smokers quit after turning 60, Zhang said.

At least one study has looked at what happens when elderly smokers quit and found a benefit, Woon-Puay Koh, an epidemiologist at Duke-NUS Graduate Medical School in Singapore, said by email.

Koh, who wasn’t involved in the current study, said her research team studied a group of elderly Singapore Chinese people who were age 60 on average when they quit smoking and found that after four years, they were 15 percent less likely to die of heart disease than current smokers.

While quitting at any age has numerous health benefits, there are some health problems that older smokers can’t completely reverse with cessation, cautioned Dr. John Laird, head of the vascular care at the University of California Davis Medical Center.

“Some of the damage to the blood vessels caused by smoking will be permanent,” Laird, who wasn’t involved in the study, said by email. “The risk of cardiovascular events for former smokers will never return to the level of a non-smoker.”