"Based on these findings, it should be as important to encourage adolescents and young adults to build broad social relationships and social skills for interacting with others as it is to eat healthy and be physically active," said Kathleen Mullan Harris, James Haar Distinguished Professor at UNC-Chapel Hill and faculty fellow at the Carolina Population Center (CPC).

The study, published in the Proceedings of the National Academy of Sciences, builds on previous research that shows that aging adults live longer if they have more social connections. It not only provides new insights into the biological mechanisms that prolong life but also shows how social relationships reduce health risk in each stage of life.

Specifically, the team found that the sheer size of a person's social network was important for health in early and late adulthood. In adolescence, that is, social isolation increased risk of inflammation by the same amount as physical inactivity while social integration protected against abdominal obesity. In old age, social isolation was actually more harmful to health than diabetes on developing and controlling hypertension.

In middle adulthood, it wasn't the number of social connections that mattered, but what those connections provided in terms of social support or strain. "The relationship between health and the degree to which people are integrated in large social networks is strongest at the beginning and at the end of life, and not so important in middle adulthood, when the quality, not the quantity, of social relationships matters," Harris said.

Harris and her team drew on data from four nationally representative surveys of the U.S. population that, together, covered the lifespan from adolescence to old age. They evaluated three dimensions of social relationships: social integration, social support and social strain. They then studied how individual's social relationships were associated with four markers shown to be key markers for mortality risk: blood pressure, waist circumference, body mass index and circulating levels of C-reactive protein, which is a measure of systemic inflammation.

One of the four nationally representative surveys was part of The National Longitudinal Study of Adolescent to Adult Health, or Add Health, the largest, most comprehensive data researchers use to study how social relationships, behavior, environment and biology interact to shape health in adolescence and influence well-being throughout adulthood.

"We studied the interplay between social relationships, behavioral factors and physiological dysregulation that, over time, lead to chronic diseases of aging -- cancer being a prominent example," Yang Claire Yang, a professor at UNC-Chapel Hill, CPC fellow and a member of the Lineberger Comprehensive Cancer Center. "Our analysis makes it clear that doctors, clinicians, and other health workers should redouble their efforts to help the public understand how important strong social bonds are throughout the course of all of our lives."

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Materials provided by University of North Carolina at Chapel Hill. Note: Content may be edited for style and length.

Journal Reference:

1. Yang Claire Yang, Courtney Boen, Karen Gerken, Ting Li, Kristen Schorpp, Kathleen Mullan Harris. Social relationships and physiological determinants of longevity across the human life span. Proceedings of the National Academy of Sciences, 2016; 201511085 DOI: 10.1073/pnas.1511085112