Being sociable is good for your heart, researchers have suggested.
Men need social contact to stay healthy, say researchers
The US study found men who do not have many close links with friends and family have higher levels of a blood molecule which indicates inflammation.
The data is being presented to a meeting of the American Heart Association.
UK heart experts said people who were socially isolated may be less active and more likely to smoke, both factors which increase heart risk.
Inflammation appears to play a role in causing atherosclerosis by allowing white blood cells to attach themselves to the side of the blood vessel wall.
This means fatty deposits can stick to the blood vessel wall more easily.
Researchers studied 3,267 men and women with an average age of 62, from across America who were taking part in the Framingham Heart Study.
They underwent medical examinations between 1998 and 2001 where researchers measured blood concentrations of four inflammatory markers including the molecule interleukin-6 (IL-6).
Participants were also asked about their marital status, the number of relatives or close friends in whom they could confide in, whether they had any involvement in religious meetings or services and participation in groups such as day centres.
From this information, the researchers assigned a social network rating of one (social isolation), to four (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.
The researchers said the difference between men with the lowest and highest rating was statistically significant.
Researchers say IL-6, and so inflammation, may be elevated in socially isolated men because they are more prone to living less healthily and that socially isolated people are more often depressed and under stress than those who are more outgoing.
However the researchers said no difference was seen between socially isolated or connected women.
Researchers say this may be because they asked about the quantity rather than the quality of relationships, which they suggest may be the crucial factor for women.
There was also no link found between other markers of inflammation in the blood and whether or not someone was sociable.
Eric Loucks, from Harvard School of Public Health in Boston, who took part in the research, said: "Our analyses suggest that it may be good for the heart to be connected.
"In general, it seems to be good for health to have close friends and family, to be connected to community groups or religious organisations, and to have a close partner."
Cathy Ross, a cardiac nurse at the British Heart Foundation, said: "The results of this study further support the evidence that raised inflammatory markers may indicate an increased risk of developing coronary heart disease.
"It identified raised markers in those who are socially isolated and linked the fact that the individuals in this group may be less active and more likely to smoke. Both of these are significant risk factors for CHD.
"Rehabilitation programmes and support groups, such as those run by the BHF, have been shown to support patients and their families, increase their confidence and reduce the incidence of isolation."