Being the life and soul of the party may cut your chances of a fatal heart or stroke
A 30-year study by Chicago Northwestern University suggested shy or antisocial men were 50% more likely to die this way, compared with outgoing men.
The Annals of Epidemiology study supports other work suggesting a link between personality and health.
A British expert said lower social status may be the root cause of both shyness and poor health.
The researchers tracked the health of more than 2,000 middle-aged men over three decades, until 60% of their subjects had died.
The death certificates were matched with psychological questionnaires filled in at the start of the study to reveal the personality type of the man in question.
The shyest group of men were 50% more likely to have died from heart attack or stroke than the group of most sociable men.
When other information about the mens' lifestyles was analysed, no link to other known risk factors, such as smoking, drinking or obesity came to light - apparently ruling out the theory that shy or unsocial men might be dying because of unhealthy, couch potato behaviour.
The researchers suggested that either that shy men are more stressed by new situations, or that the setting of their personality type is in some way linked to the part of the the brain that controls the smooth operation of the heart.
Decades of research suggest there is only one personality type which is not linked to an increase risk of serious disease.
Easy going people - so-called type "B" personalities - appear to be the healthiest.
Type "A" personalities - driven workaholics prone to stress and anger, are more likely to suffer high blood pressure and heart disease, while Type "C" people, who suppress their feelings, have been connected to an increased risk of cancer.
Other research projects have connected Type "D" people, pessimists with low self-confidence, with heart attack or stroke.
Dr Eric Brunner, an epidemiologist at University College London, said that similar work carried out by him and his colleagues suggested a connection between social status and poor health.
He said it was possible that feeling socially inferior - which could contribute to a shy personality - could introduce unhealthy changes in lifestyle and behaviour, or even disrupt the balance of the body's hormones.
"What we shouldn't say to people is that if you're shy, you're going to die of a heart attack.
"This research is interesting, and may be showing one of the pathways by which lower social status is connected to disease.
"It suggests that social anxiety is very important - one of the reasons that a hierarchy exists is because people feel that they participate to a greater or lesser extent in the activities of the society in which we live."
Shy men 'more prone to heart attacks'
Shy men '50% more likely to die of heart disease'
Are you the shy, retiring type? Watch your heart