Studies have shown that lonely people are at risk of not being as healthy and their risk of premature death is increased, but the reason for this was unclear. Recently, researchers found out that “loneliness may trigger cellular changes that might lower a person’s ability to fight viral infections.”

141 adults participated in the study, 36 were “chronically lonely”. Researchers were looking at the relationship between patterns of gene expression in white blood cells (which protect the body against viruses and bacteria) with loneliness.

Cells in the “chronically lonely” people showed signs of an increased expression of the genes that are involved with fighting bacterial infections and inflammation, compared with the cells of other participants.

John Cacioppo, a psychologist at the University of Chicago said that gene expression is changing the body to show an inflammatory response. However, this response occurs at the cost of the ability to fight viral infections as it puts the body in a state of preparation for bacterial infection.

This means that lonely people are more protected from bacteria, because the shift occurred and protection against viruses decreased.

This finding suggested that there is a correlation between pro-inflammatory pattern of gene expression and loneliness. The researchers found that one year later “chronically lonely” people were still likely to have the pro-inflammatory pattern of gene expression and those with this pattern at the beginning of the study were still lonely.

Third variables such as depression, degree of social support and stress level would not explain these results.

Another study was made, where researchers found the same pre-inflammatory shift among lonely macaque monkeys. The shift may be related to an output of immature cells monocytes from the immune system, which levels of expression of inflammatory proteins are high and levels of gene expression of antiviral protein are low.

The scientists state that pro-inflammatory changes affected the monkey’s health. The researchers found that virus grew faster in lonely monkeys rather than in the monkeys that were not lonely after those were infected with simian immunodeficiency virus, which is a monkey version of HIV.

Cacioppo said that more advanced disease was shown in lonely monkeys and not in the nonlonely ones.

The scientists want to continue these studies and are planning to find out how loneliness leads to poor health condition and how it can be prevented in elders.