This report by the National Institute on Aging (part of the US Department of Health and Human Services) looked at the links between social isolation and loneliness and the higher risks that they posed for a variety of physical and mental conditions: high blood pressure, heart disease, obesity, weakened immune systems, anxiety, depression, cognitive decline, Alzheimer’s disease and even death.
The report noted that people who find themselves unexpectedly alone due to the death of a spouse or partner, separation from friends or family, retirement, loss of mobility, and lack of transportation are at particular risk. Conversely, people who engage in meaningful, productive activities with others tend to live longer, boost their mood, and have a sense of purpose. These activities seem to help maintain their well-being and may improve their cognitive function.
Chronic loneliness activates a biological defence mechanism which, according to Steve Cole, Ph.D., director of the Social Genomics Core Laboratory at the University of California, Los Angeles, acts like a fertilizer for other diseases. He noted that “The biology of loneliness can accelerate the build-up of plaque in arteries, help cancer cells grow and spread, and promote inflammation in the brain leading to Alzheimer’s disease. Loneliness promotes several different types of wear and tear on the body.”
People who feel lonely may also have weakened immune cells that have trouble fighting off viruses, which makes them more vulnerable to some infectious diseases. Loneliness may indeed alter the tendency of cells in the immune system to promote inflammation, which is necessary to help our bodies heal from injury
H Eating 23rd April 2019 National Institute on Aging.