WASHINGTON, D.C., May 1 -- Being social has its rewards.
Men who are socially isolated have elevated levels of a blood marker for inflammation that's linked to cardiovascular disease, according to data from the Framingham Heart Study presented today at the American Heart Association's 45th Annual Conference on Cardiovascular Disease Epidemiology and Prevention.
"Our analyses suggest that it may be good for the heart to be connected," said Eric B. Loucks, Ph.D., an instructor in the department of society, human development and health at Harvard School of Public Health in Boston. "In general, it seems to be good for health to have close friends and family, to be connected to community groups or religious organizations, and to have a close partner."
Loucks' team studied 3,267 Framingham Heart Study participants, with an average age of 62 years, who underwent physical exams between 1998 and 2001. The researchers measured blood concentrations of four inflammatory markers including interleukin-6 (IL-6).
The researchers asked the participants five questions about their social network:
- marital status;
- number of relatives in whom they can confide private matters;
- number of close friends in whom they can confide private matters;
- involvement in religious meetings or services; and
- participation in groups such as senior centers.
They then assigned a social network index of 1 to 4, based on participants' response, with the lowest number corresponding to social isolation and the highest to high social connection.
After considering major known risk factors for heart disease, men with the lowest level of social involvement had the highest levels of IL-6, the study showed. Specifically, the average concentration of IL-6 in the blood of men with a social network index of 1 was 3.85 picograms per milliliter, compared with 3.52 picograms per milliliter in men with a social network index of 4. "This was a statistically significant difference," Loucks said.
No such link was found in women, however. Researchers noted that the study counted the number of relationships, but did not assess the quality of relationships. For example, were these relationships supportive for the study participants, or did they often cause stress and conflict? Future studies on the quality of relationships will provide knowledge on the effect of social relationships on inflammatory markers in women.
Also, researchers found no association between social involvement and three other markers of inflammation in the blood: C-reactive protein, soluble intercellular adhesion molecule-1 and monocyte chemoattractant protein-1. "These observations need further study," Loucks said.
Studies indicate that inflammation plays a role in causing atherosclerosis. "It seems to allow white blood cells to tether to and become engulfed in the side of the blood vessel wall," Loucks said. "This allows lipids to be deposited in the blood vessel wall more easily, causing atherosclerosis."
Researchers say IL-6 -- and by extension, inflammation -- may be elevated for two reasons in men who are socially isolated. First, social isolation may influence health behaviors such as smoking and physical activity, which in turn affect IL-6 levels. Second, socially isolated people are often depressed and under more stress than their more outgoing counterparts (studies show that even acute stress can increase levels of IL-6).
Co-authors include Lisa M. Sullivan, Ph.D.; Ralph B. D'Agostino, Ph.D.; Martin G. Larson, Sc.D.; Lisa F Berkman, Ph.D.; and Emelia J. Benjamin, M.D., Sc.M.
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