Feeling lonely may hurt your heart in more ways than one.

A University of Chicago study of 229 men and women between the ages of 50 and 68 showed that those who said they lacked companionship were more likely to have elevated blood pressure, a risk factor for heart disease.

People who felt the loneliest had systolic blood pressures (the top number) 10 to 30 mm Hg higher than those who felt the least lonely. Though the extent of the rise in blood pressure increased with age, the link between loneliness and blood pressure remained after accounting for age, weight, smoking, depression, and other risk factors for hypertension.

The authors of the study point out that the magnitude of the effects of loneliness on blood pressure was as great as the reduction in blood pressure expected to result from weight loss or increased exercise.

There's more news linking loneliness and the risk of cardiovascular disease. A Harvard study has shown an association between loneliness among men and an increase in a type of inflammation linked to cardiovascular disease. In addition, a Duke study has found that socially isolated patients with heart disease have a higher risk of death.

These findings are especially significant now, as the U.S. population is aging and more people are living alone. Some research suggests that a feeling of isolation and a lack of companionship may affect more than 11 million elderly Americans as friends and family move, become ill, or die.

I agree with the authors of the Chicago study, who suggest paying more attention to family and friends and getting involved in volunteer work and other activities that make you feel useful.