Having to walk further from home to get to a tobacco shop increases the odds that smokers will quit, according a large study in Finland.

Researchers found that every 500-meter (about one third of a mile) increase in distance to the nearest tobacco shop increased an individual's odds of quitting by 20 percent to 60 percent.

"We anticipated that distance to a tobacco shop may play a role in smoking habits," said senior author Dr. Mika Kivimaki of University College London and the Finnish Institute of Occupational Health in Helsinki. "But it was a surprise that the association was so strong."

The researchers combined the results of two previous studies that together included more than 20,000 smokers and former smokers. Participants completed smoking behavior surveys twice, three to nine years apart, and the researchers geocoded their residential addresses and locations of the nearest tobacco outlet.

At the beginning of the two studies, participants included 6,259 current smokers in one study and 1,090 in the other. By the second wave of surveys, 28 percent and 39 percent, respectively, had quit smoking.

Between surveys, 39 percent of study participants had also changed residential address.

Those who moved at least 500 meters further from a tobacco outlet were about 16 percent more likely to quit than people who remained at the same distance from the nearest shop.

More on this...

On the individual level, a person who moved 500 meters further away during the study was 57 percent more likely to quit after the move, even when the researchers accounted for marriage, health status and changes in financial situation that might affect risk for smoking relapse.

Of those who were former smokers at the beginning of the study period, about 7 percent had relapsed by the second surveys, though relapse was not associated with distance to a tobacco outlet, according to the results in JAMA Internal Medicine.

"We know that most smokers would like to stop smoking, but this is difficult because cigarettes include addictive substances," Kivimaki told Reuters Health by email. "Perhaps, a longer distance to a tobacco shop makes the decision to quit smoking a bit easier."

Moving further from a tobacco source, or removing the nearest source, ups the odds of quitting, and policymakers might be able to harness this association, he said.

"Our findings are consistent with a more general principle, 'Make the healthier choice the easier choice,'" Kivimaki said. "Reduced availability of tobacco products, which was supported by our findings, complements public health policies that aim to create environments that facilitate integration of physical activity into daily lives and legislation that support healthful diet choices."

But it's unclear whether the results apply to workplaces as well, or only to residential areas, he said.

"We can now conclude that tobacco outlets and the heavy dose of tobacco marketing they dump into their communities cause smoking - more precisely, they inhibit quitting among smokers," Dr. Cheryl Bettigole and Dr. Thomas A. Farley of the Philadelphia Department of Public Health write in a commentary published with the findings.

Globally and in some areas of the U.S., policies attempt to address the community risk factor of smoking retail outlets, they note. San Francisco limits the number of tobacco licenses granted per supervisorial district and New Orleans limits tobacco retailers near schools, they write.