Category Archives: smoking

Having few friends predicts early death as much as smoking or alcoholism

“Low social interaction as high a risk factor for early death as smoking 15 cigarettes daily or being an alcoholic, and twice the risk factor of obesity.”

Julianne Holt-Lunstad, a psychologist at BYU, published a recent meta-analysis with Timothy Smith and J. Bradley Layton (that culls from learning across 148 longitudinal health studies covering over 300,000 individuals). They showed that increased involvement in social networks on average reduces one’s chance of mortality over the period of any particular study by 50+%, a greater effect than either stopping smoking or eliminating one’s obesity/physical inactivity.

The study “Social Relationships and Mortality Risk: A Meta-analytic Review” appears in the journal PLoS Medicine.  They controlled for baseline health status,  and found consistent results for friendships with family, friends, neighbors and colleagues across age, gender, initial health status, cause of death, and follow-up period.

The life-protective benefits of friendship were strongest for complex measures of social integration and lowest for simple measures of residential status (e.g., living alone versus with others) .  In studies that had greater dimensions of social involvement (whether one was in a network, the kinds of social support one got, etc.), the life-protecting benefits of friendships were higher, likely corresponding to the multiple pathways through which friendships provide benefits.

Low social interaction, according to the authors, was as high a risk factor for early death as smoking 15 cigarettes a day or being an alcoholic.  Low social interaction was a higher risk factor than not exercising and twice as high a risk factor for early death as obesity.

Co-author Tim Smith noted: “We take relationships for granted as humans – we’re like fish that don’t notice the water….That constant interaction is not only beneficial psychologically but directly to our physical health.”

The longitudinal studies they analyzed tracked health outcomes and social interaction for a period of seven and a half years on average.

The 50% increased survival rate is quite likely an underestimate: these longitudinal studies don’t track relationship quality but only one’s inclusion in a social network, so they include negative relationships as well. Survival benefits of friendships are likely to be much higher if one could isolate only positive and healthy social relationships.

Holt-Lunstad speculated that the pathways of social relationships to improved longevity stem range from  “a calming touch to finding meaning in life.” She believes that those who are socially connected take greater responsibility for others’ and their own lives and take fewer risks.

Here is key Figure 6 from their study:

Unlike some other work, such as Eric Klinenberg’s Heat Wave, where shut-in elderly were especially at risk of death in Chicago’s 1995 heat wave, the findings of Holt-Lunstad are generalizable to all age groups.

Quit your habit in groups and be more popular, say scientists

Nick Christakis and James Fowler made headlines recently for their study on obesity contagion (See Can your friends affect your weight?).

Now they’re back with analogous research that shows that you are far more likely to be able to quit smoking if you do it in groups (where those around you are also quitting). It’s scientifically-proven, but something that practitioners have known for a while: why do you think Jenny Craig has dieters work in groups, or why all the self-help groups (Alcoholics Anonymous and others of that ilk) use group norms to reinforce changes in behavior.

Study co-author Fowler notes that in tracking individuals and social groups (through the Framingham Heart Study) over 30-years, the average size of each cluster of smokers was of similar size, but Fowler notes: “It’s just that there are fewer and fewer of these clusters as time goes on.”

The social contagion of quitting smoking can extend to people that the quitter didn’t know. For example if Anne quits smoking, and Anne is friends with Barb and Barb is friends with Clarissa, Clarissa’s chance of quitting increases by 30%, even if Anne and Clarissa don’t know each other.

Christakis notes that smokers have moved more to the periphery of social networks, where they often were more at the center of these social networks several decades ago. While this doesn’t say that teen non-smokers will necessarily be more popular, it does suggest over their lifespan that non-smoking is more likely to be associated with popularity than smoking.

The obesity study appears in the May 22 issue of the New England Journal of Medicine.

See also, Clive Thompson, “Is Happiness Catching?” (NYT Sunday Magazine, 9/13/09)

The Smoking Gun: Friends influence your smoking and quitting

New research by Professor Edward Glaeser (director of Harvard Kennedy School’s Taubman Center for State and Local Government) and David Cutler (economics professor at Harvard) shows that people are more likely to smoke when surrounded by smokers.  But positively, it shows a multiplier effect of smoking bans: those who quit smoking in turn influence their friends and spouses to stop smoking.

More specifically, “individuals whose spouse faced a workplace smoking ban were less likely to smoke themselves. The estimates suggest a 40 percent reduction in the probability of being an individual smoking if a spouse quits,” the authors write.   Cutler and Glaeser think that policy makers should consider these multiplier benefits when they are considering enacting smoking bans.

For more detail you can read their Kennedy School Working Paper, “Social Interactions and Smoking.”

I posted earlier on research on the sociological dynamics of obesity, depression, and some prior evidence on smoking (read further down in this link).

Can your friends affect your weight?

Nicholas Christakis (at the Harvard School of Public Health) (together with James Fowler at U. Cal. San Diego) has done very interesting research with the landmark Framingham Heart Study looking at the likelihood of obesity. They find, after tracking some 12,000 individuals through the 32-year long study (1971-2003), that even controlling for all the genetic markers for obesity (like parents’ obesity) and weight at the study’s baseline, having fat friends increases the chance that you will be fat.  [The Framingham study participants could list only up to 3 friends, so the friends being discussed here are closer, stronger friends, rather than weaker ties.]

Having an obese friend increased one’s likelihood of obesity by 57%, with a smaller effect for siblings and spouses. This risk of developing obesity rose to 171% for the closest mutual friendships. Having very large neighbors had no effect on obesity if those neighbors weren’t friends of the individual in question.

The study found that the network impact of friends on obesity could be seen in as small as 2-4 year increments.

Christakis discounted other likely factors such as environmental (since it didn’t matter how close geographically ones’ friends were, making it less likely that they are both responding to something in the neighborhood, for example).  They did code the data for density of fast food restaurants and it did not make this effect go away.  [The fact that long-distance close friends influence obesity as much as nearby close friends is very surprising;  for sure, if respondents are still listing this long-distance friend as one of their three closest friends, they must have stayed in regular contact, but I would have thought that obese friends made respondents feel more comforable being obese partly by physically seeing an obese friend, and this is presumably less common with geographically distant friends.

And Christakis thinks the mechanism is “induction”; having an overweight person list YOU as their friend doesn’t increase your likelihood of being obese, but your listing an overweight person as YOUR friend does.  The impact of these friendships decreases with social distance (in other words, your friends affect your weight more than your friends’ friends, which is more consequential than the weight of your friends’ friends’ friends, etc.) but they still have an impact out to three degrees of separation.  And same sex friends influence your weight gain more than opposite sex friends.

Christakis thinks that people with heavier friends either come to think of themselves as less fat or else it validates their obesity in a way that wouldn’t be the case if their friends were thinner.  (But the study showed that it wasn’t the simple story of a change in physical exercise or eating habits from these friends.)  And there is homophily in obesity — in other words, fat people are more likely to choose overweight friends and thin people are more likely to pick thin friends.  And if overweight people have thin friends or vice-versa, these relationships tend to be less stable over time (the thin people are more likely to drop their overweight friends or become more obese).

The New York Times notes that: “Science has shown that individuals have genetically determined ranges of weights, spanning perhaps 30 or so pounds for each person. But that leaves a large role for the environment in determining whether a person’s weight is near the top of his or her range or near the bottom. As people have gotten fatter, it appears that many are edging toward the top of their ranges. The question has been why. ” (“Find Yourself Packing It On? Blame Friends, NYT, 7/26/07).  The study suggests that social contagion of obesity through networks may be the explanation.

Christakis thinks that the role of social networks may be one of the explanations for the increasing obesity in America (along with other factors like exercise, change in eating habits like supersizing of food and more fast food and soft drinks, etc.).  The social networks may have changed norms and made weight gains more acceptable, even outside of any change in behavior.    Moreover Christakis thinks that we might be able to use the structure of social networks to fight obesity, by for example fighting obesity in groups rather than with individuals.  If there can be a social contagion of obesity, how might we start a social contagion of weighing less?  Co-author James Fowler noted that having a friend that was able to lower his or her weight down made it easier for one to lose weight; that’s why weight loss programs often function using groups, to reinforce the attempted change in behavior. But this question of spurring a social contagion for good is exactly the kind of question that Malcolm Gladwell in The Tipping Point considers.

Christakis and colleagues have also found similar network properties in this study to the spread of smoking, but the cessation of smoking was not a factor in individuals gaining weight or not.

Finally Christakis thinks that we may undervalue health interventions since we look only at the impact of the intervention on one individual rather than examining the multipliers on this investment through his/her social network.

The authors note that there are many social and health benefits of  friendship so their study is not a reason not to develop friends with anyone.

Follow-up posts on this study available here, and here.

The Christakis et al article is published today in the New England Journal of Medicine and a summary of some of the findings is available in this Harvard Gazette story.

There’s a neat visual representation of the obesity spreading through the social networks over time in this video.

See also, Clive Thompson, “Is Happiness Catching?” (NYT Sunday Magazine, 9/13/09)