|Smokers Flock Together and Quit Together
Social Networks Exert Key Influences on Decision to Quit Smoking
When smokers kick the habit, odds are they are not alone in making
the move. Instead, the decision to quit smoking often cascades
through social networks, with entire clusters of spouses, friends,
siblings and co-workers giving up the habit roughly in tandem,
according to a new study supported in part by the National Institutes
of Health (NIH).
Researchers analyzing changes in smoking behavior over the past
three decades within a large social network found smokers quit
in groups and not as isolated individuals. Those who continued
to smoke also formed clusters that, over time, shifted from the
center of the social network, where social connections are more
numerous, to the periphery of the group. The report, appearing
in the May 22, 2008, New England Journal of Medicine and
funded primarily by the National Institute on Aging (NIA), part
of the NIH, could play a role in developing clinical and public
health interventions to reduce and prevent smoking. The smoking
analysis was also supported by the Robert Wood Johnson Foundation.
Researchers Nicholas A. Christakis, M.D., Ph.D., of Harvard Medical
School, and James Fowler, Ph.D., of the University of California,
San Diego, based their analysis on a social network of 12,067 people
participating in the Framingham Heart Study (FHS). The FHS, a community-based
study sponsored for 60 years by the NIH's National Heart,
Lung and Blood Institute (NHLBI), collects comprehensive measures
of cardiovascular health and risk factors among three generations
of participants who are connected as family, friends and co-workers.
Christakis and Fowler analyzed data collected on the network’s
smoking behaviors between 1971 and 2003. The group ranged in age
from 21 to 70; individuals smoking one or more cigarettes a day
were deemed smokers.
The researchers found that smoking rates among the FHS participants
mirrored the national downward trend of the past three decades.
In 1971, there were many more smokers and they tended to mix equally
with nonsmokers. But by 2000, along with a drop in smoking rates,
there was also a change in their social lives. Smokers and nonsmokers
tended to form separate clusters, and gradually, the smokers were
marginalized on the fringes of the social network.
"While smoking has declined significantly over the past 30
years in America, it remains a leading cause of preventable death," said
NIA Director Richard J. Hodes, M.D. "This study tells us that
social relationships have a critical impact on health behaviors
and decisions, and that people are strongly influenced by those
in their social sphere."
The researchers found the closer the relationship between contacts,
the greater the influence when one person quit smoking. For example:
- When a husband or wife quit, it decreased the chance of their
spouse smoking by 67 percent.
- When a sibling quit, it reduced the chance of smoking by 25 percent
among their brothers and sisters.
- A friend quitting decreased the chance of smoking by 36 percent
among their friends.
- In small firms, a co-worker quitting could decrease smoking
among peers by 34 percent. In larger firms,
the influence was insignificant.
- Neighbors did not seem to be influenced by each other’s smoking
"Interestingly, geography did not appear to play a role because
smoking behaviors spread between contacts living miles apart and
in separate households," said Christakis. "Rather, the
closeness of the relationship in the network was key to the spread
of smoking behaviors."
Fowler and Christakis also found specific patterns in the spread
of behaviors. For example, the higher the educational levels among
the contacts, the greater the influence on smoking behavior. Among
friends who both had at least one year of college, a decision by
one friend to quit smoking decreased the chance of the other smoking
by 61 percent. However, no such influence was found in pairs of
friends with a high school education or less. The more highly educated
smokers also appeared to pay a greater social price for smoking,
as reflected in the fact that they became less central to the network
than did the less educated.
"This study has an essential public health message — that
no one is an island — our health is partially determined
by our social networks and those around us," said Richard
Suzman, Ph.D., director of the NIA’s Division of Behavioral and
Social Research. "The decision to quit smoking cascaded throughout
the web, indicating that some form of collective decision-making
was taking place. 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."
Christakis and Fowler have previously studied the effect of social
networks on the spread of obesity. To learn more about this research,
The NIA leads the federal effort supporting and conducting research
on aging and the medical, social and behavioral issues of older people.
For more information on research and aging, go to www.nia.nih.gov.
The NHLBI conducts and supports research related to heart, blood
vessel, lung and blood diseases, and sleep disorders. To learn
more about this research and related national health education
campaigns, including a Chronic Obstructive Pulmonary Disease (COPD)
awareness campaign, go to www.nhlbi.nih.gov.
The National Institutes of Health (NIH) — The Nation's
Medical Research Agency — includes 27 Institutes and
Centers and is a component of the U.S. Department of Health and
Human Services. It is the primary federal agency for conducting
and supporting basic, clinical and translational medical research,
and it investigates the causes, treatments, and cures for both
common and rare diseases. For more information about NIH and
its programs, visit www.nih.gov.