The Buddy System: How Medical Data Revealed Secret to Health and Happiness
A revolution in the science of social networks began with a stash of old papers found in a storeroom in Framingham, Massachusetts. They were the personal records of 5,124 male and female subjects from the Framingham Heart Study. Started in 1948, the ongoing project has revealed many of the risk factors associated with cardiovascular disease, including smoking and hypertension.
In 2003, Nicholas Christakis, a social scientist and internist at Harvard, and James Fowler, a political scientist at UC San Diego, began searching through the Framingham data. But they didn't care about LDL cholesterol or enlarged left ventricles. Rather, they were drawn to a clerical quirk: The original Framingham researchers noted each participant's close friends, colleagues, and family members.
"They asked for follow-up purposes," Christakis says. "If someone moved away, the researchers would call their friends and try to track them down."
Christakis and Fowler realized that this obsolete list of references could be transformed into a detailed map of human relationships. Because two-thirds of all Framingham adults participated in the first phase of the study, and their children and children's children in subsequent phases, almost the entire social network of the community was chronicled on these handwritten sheets. It took almost five years to extract the data—the handwriting was often illegible—but the scientists eventually constructed a detailed atlas of associations in which every connection was quantified.
The two researchers thought the Framingham social network might demonstrate how relationships directly influence behavior and thus health and happiness. Since the study had tracked its subjects' weight for decades, Christakis and Fowler first analyzed obesity. Clicking through the years, they watched the condition spread to nearly 40 percent of the population. Fowler shows me an animation of their study—30 years of data reduced to 108 seconds of shifting circles and lines. Each circle represents an individual. Size is proportional to body mass index; yellow indicates obesity. "This woman is about to get big," Fowler says. "And look at this cluster. They all gain weight at about the same time."
In 1948, fewer than 10 percent of Framingham residents were obese. By 1985, 18 percent were, and today about 40 percent are. What changed? Social norms of diet and physical appearance. "A bunch of people discovered fast food at the same time," social scientist Christakis says. "Then the network took over."
*Circle size corresponds to body mass index
Images based on graphics created by James Fowler and Nicholas Christakis