Is Exercise Contagious? Peer Effects in a global Health Behavior

We leveraged exogenous variation in weather patterns across geographies to identify social contagion in exercise behaviors across a global social network. We estimated these contagion effects by combining daily global weather data, which creates exogenous variation in running behaviors among friends, with data on the network ties and daily exercise patterns of ~1.1 million individuals who ran over 350 million kilometers in a global social network over five years. Our analysis showed that exercise is socially contagious and that its contagiousness varies with the relative activity levels of and gender relationships between friends. Less active runners influence more active runners, while the reverse is not true. Both men and women influence men, while only women influence other women. While the Embeddedness and Structural Diversity theories of social contagion explained the influence effects we observed, the Complex Contagion theory did not. These results suggest that interventions should account for social contagion to spread behavior change more effectively.

Short Bio:
Christos Nicolaides is the James McDonnell Postdoctoral Fellow in complex systems at the Information Technology group at MIT Sloan School of Management and a member of the Initiative in Digital Economy (IDE) at MIT. His research interest includes social influence in complex networks, digital media, and the design of effective digital strategy. He currently works on a large-scale research project in collaboration with global exercise tracking company to identify how social influence impacts the fitness habits of individuals. Before joining at Sloan School, Christos completed his PhD degree at the Civil and Environmental Engineering department at MIT, where he worked on understanding human mobility as well as the mechanisms of disease spreading in social and transportation networks. He holds a bachelor degree in Physics and a master degree in Applied Mathematics from Imperial College London. He is the leading author of 5 journal and 8 conference publications and he is the recipient of multiple academic awards and one principal investigation grant.