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6-10-08

Smokers band together and quit together

When smokers kick the habit, chances are they're in good company. A new study finds that changes in smoking behavior often spread through social networks, with spouses, friends, siblings and co-workers deciding to light up or stub out their cigarettes for good around the same time. A better understanding of how social networks affect smoking behavior may lead to more effective ways to prevent or reduce smoking.

Smoking rates nationwide have dropped significantly over the past four decades. Still, it remains the leading cause of preventable death in the United States. Previous studies have shown that social ties between two people—especially young people—can influence decisions to start or stop smoking. But the effects of more complex and dynamic social groupings have been unclear.

Dr. Nicholas A. Christakis of Harvard Medical School and Dr. James Fowler of the University of California, San Diego, decided to look at smoking patterns and social ties in a broader context. With funding from NIH’s National Institute on Aging (NIA) and the Robert Wood Johnson Foundation, the researchers examined medical records and other data from more than 12,000 adults who had participated in the Framingham Heart Study, a long-term community-based study sponsored by NIH's National Heart, Lung and Blood Institute (NHLBI). Because participants regularly provided updated contact information about their family, friends and coworkers, Christakis and Fowler were able to track changes in social relationships over more than three decades, from 1971 to 2003.

The researchers reported in the May 22, 2008, issue of the New England Journal of Medicine that smoking rates within the study group mirrored the national downward trend of the past few decades. In 1971, more of the study participants were smokers, and they tended to mix equally with nonsmokers. But by 2000, along with a decline in smoking, there was also a change in their social lives. Smokers and nonsmokers tended to form separate clusters. Eventually, the smokers were marginalized on the fringes of the social network, with fewer social ties to others.

The researchers also found that closer relationships seemed to exert a strong influence on smoking, with the greatest effect within married couples. When a husband or wife quit smoking, it reduced the chance of their spouse smoking by about 67 percent. Quitting decreased the likelihood of smoking among friends by about 36 percent, and a similar influence was seen among coworkers at small firms. Siblings seemed to have a slightly smaller influence, with quitting reducing the chance of smoking in a brother or sister by 25 percent.

Last year, Christakis and Fowler reported the results of a similar study that looked at the spread of obesity within this same large social network. Together, the two studies suggest that social ties can have both positive and negative effects on health-related behaviors.

"Our health is partially determined by our social networks and those around us," said Dr. Richard Suzman, director of NIA's Division of Behavioral and Social Research. "The results suggest new and probably more powerful approaches to changing health behaviors, such as smoking, by careful targeting of small peer groups as well as single individuals."

For further information on this and other health topics, visit the web site of the National Institute of Health at www.nih.gov.