The study is the first to definitively link social relationships with concrete measures of physical wellbeing such as abdominal obesity, inflammation, and high blood pressure, all of which can lead to long-term health problems, including heart disease, stroke and cancer.
"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, Professor at University of North Carolina (UNC) in US.
The study 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.
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In adolescence, 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.
"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.
The researchers drew on data from four nationally representative surveys of the US population that covered the lifespan from adolescence to old age.
They evaluated three dimensions of social relationships - social integration, social support and social strain.
"We studied the interplay between social relationships, behavioural factors and physiological dysregulation that, over time, lead to chronic diseases of ageing - cancer being a prominent example," said Yang Claire Yang, a professor at UNC.
"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," Yang said.