John Cacioppo, a professor of psychology at the University of Chicago, and colleagues said the impact of loneliness on premature death was nearly as strong as the impact of disadvantaged socioeconomic status, which they found increases the chances of dying early by 19 percent.
The issue was discussed Sunday at the annual meeting of the American Association for the Advancement of Science in Chicago.
A 2010 meta-analysis showed loneliness has twice the impact on early death as does obesity, Cacioppo said.
Researchers looked at dramatic differences in the rate of decline in physical and mental health as people aged. They also examined the role of satisfying relationships on older people to develop their resilience -- the ability to bounce back after adversity and grow from stresses in life.
The consequences to health were dramatic. Feeling isolated from others can disrupt sleep, elevate blood pressure, increase morning rises in the stress hormone cortisol, alter gene expression in immune cells and increase depression and lower overall subjective well-being, Cacioppo said.
Cacioppo said older people can avoid the consequences of loneliness by staying in touch with former co-workers, taking part in family traditions and sharing good times with family and friends -- all ways to connect others about whom they care and who care about them.
"Retiring to Florida to live in a warmer climate among strangers isn't necessarily a good idea if it means you are disconnected from the people who mean the most to you," Cacioppo said in a statement released by the University of Chicago.
Population changes make understanding the role of loneliness and health all the more important, he explained.
Cacioppo and his colleagues identified three core dimensions to healthy relationships -- intimate connectedness, which comes from having someone in your life you feel affirms who you are; relational connectedness, which comes from having face-to-face contacts that are mutually rewarding; and collective connectedness, which comes from feeling that you're part of a group or collective beyond individual existence.
It is not solitude or physical isolation itself, but rather the subjective sense of isolation that is so profoundly disruptive, Cacioppo said.
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