Yes, You Can Catch Obesity From Your Coworkers

SMITH BRAIN TRUST — Can you catch bad health habits from your peers? How about from your subordinates or even your boss? Yes, according to new work from the Robert H. Smith School, at the University of Maryland.

Researchers have long sought to measure the degree to which health-related traits like obesity, smoking and depression are "contagious," but they have always faced one particularly daunting challenge: How do you know whether a social bond led someone to smoke, for instance, or whether two people became friends because of shared interests and traits (including smoking or the inclination to smoke)? That difficulty hangs over all work on this subject.

In an attempt to settle the question, Maj. Vickee Wolcott, who completed a Ph.D. from the Smith School in August, took advantage of a unique aspect of military life. Soldiers are re-assigned to new units every few years, plunging them into new social worlds they did not choose. By examining a dataset that included the anonymized health records of 820,000 active-duty soldiers, from 2011 through 2014, she demonstrated that the health cultures of soldiers' new units influenced their weight, their drinking and their smoking.

The Army's strict hierarchy also allowed Wolcott to isolate the effects on behavior of peers, subordinates and superiors. "That's not something that has been done before in the literature," Wolcott says, "even though outside the Army there are lots of contexts in which you might see these different levels of influence." Think of the civilian workplace, for example, or schools and colleges — where teachers influence students, and vice versa.

Obesity, smoking and alcohol are significant problems within the Army (and, naturally, outside it). In 2014, 24 percent of soldiers were classified as obese, 36 percent used tobacco, and 17 percent met the definition of alcohol abusers.

The study, part of Wolcott's dissertation, identified a social-influence component for all three health issues, but the strength of social influence varied, as did the direction of influence. In general, peers — unsurprisingly — had stronger influences on behavior than superiors or subordinates. Of the traits studied, "obesity spreads most easily within and between rank groups," Wolcott writes.

Junior soldiers (enlisted men and women) saw their odds of obesity rise 1.4 percent for every percentage-point increase in junior-soldier obesity rates. The behavior of superiors also shaped that of junior soldiers. Junior soldiers' odds of obesity increased 1.2 percent for every percentage-point increase in the obesity rates of mid-level soldiers. Those odds rose .3 percent for every percentage-point increase in the obesity rate of senior soliders (that is, high-ranking officers and non-commissioned officers).

Mid-level soldiers had a greater risk of obesity, as well, if their peers or their superiors were obese. And senior-level soldiers were influenced by the people they oversaw.

Tobacco use was contagious, although social transmission was less intense than was the case for alcohol. Tobacco use spread "moderately through peers and less through subordinates and leaders," Wolcott writes.

Meanwhile, alcohol abuse spread among peers and down from senior leaders. It did not spread upward, from lower-level soldiers.

Wolcott also studied one positive health trait: quitting smoking. It was socially transmitted among peers at the junior and middle levels. It did not seem to spread to new senior soldiers.

An Army officer who has been served in Afghanistan, Wolcott is now an assistant professor at the Army-Baylor University Graduate Program in Health and Business Administration at Joint Base San Antonio, Fort Sam Houston, Texas. She has been assigned to various bases during her twelve-year military career, and says the finding are consistent with intuition. "You get a feeling that there are different health cultures that have been perpetuated over time," she says. But even she was surprised that she was able to delineate the influence of those cultures so precisely.

She hopes the research alerts soldiers — civilians, too — to the fact that their health is influenced by social environments, so they take precautionary measures. Wolcott also hope to parse the data further in order to alert the Army to bases that have particularly poor health cultures.

Wolcott's advisers were Gordon Gao and Ritu Agarwal, co-directors of the Center for Health Information and Decision Systems (CHIDS).

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"Precipitating Health Behavior Change: The Role of Technology and the Social Environment" was accepted as a Ph.D. dissertation at the Robert H. Smith School of Business in August 2015.

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