Why you should get a partner: Scientists reveal being lonely increases chances of dying early

Lonely people are more likely to die early due to their immune system being weaker, a new study has found.

People who do not have frequent interaction with others are 14 per cent more likely to die early as they appear to have much lower levels of white blood cells in their body.

The cells are the human body's way of battling diseases and illnesses and researchers stressed their findings were independent of other factors such as depression, stress and social support.

Research shows loneliness leads to fight-or-flight signalling occurring in the body, which can lead to a drop in white blood cells for over a year weakening the immune system.

University of Chicago scientists examined gene expression in leukocytes, there are cells responsible for protecting us against bacteria and viruses.

Their previous study found a link between loneliness and a phenomenon called 'conserved transcriptional response to adversity' (CTRA).

CTRA describes the effect of lonely people tending to have a weaker immune system response than those with a healthy social life.

This occurs when the number of genes involved in inflammation increases and the amount of genes involved in antiviral responses falls.

The PNAS study reconfirmed these findings, but also revealed that loneliness could predict future CTRA gene expression over a year later.

The researchers also found that loneliness and leukocyte gene expression appeared to provoke each other over time.

Next, research on monkeys found that the lonely primates showed higher CTRA activity.

But on a cellular level, they also found higher levels of the fight-or-flight neuro transmitter, norepinephrine.

Research conducted previously has revealed norepinephrine can provoke stem cells in the bone marrow to produce more of a particular kind of immune cell - an immature monocyte.

These particular cells have high levels of inflammatory gene expression and low levels of antiviral gene.

Further tests found both lonesome humans and solitary monkeys had high levels of monocytes in their blood samples.

Finally the researchers tracked the HIV version of monkeys (simian immunodeficiency virus) in isolated primates.

They found the altered antiviral gene expression in "lonely like" monkeys allowed the condition to grow faster in both blood and brain.

Professor John Cacioppo said: "Taken together, these findings support a mechanistic model in which loneliness results in fight-or-flight stress signalling, which increases the production of immature monocytes, leading to up-regulation of inflammatory genes and impaired anti-viral responses.

"The 'danger signals' activated in the brain by loneliness ultimately affect the production of white blood cells.

"The resulting shift in monocyte output may both propagate loneliness and contribute to its associated health risks."