The Impact of Social Connections on Immunity and Disease Risk

Loneliness and social isolation are not merely emotional challenges but significant risks to physical health. While numerous studies have focused on the psychological benefits of social connections, their physical health implications have been understudied. A study by the University of Cambridge and Fudan University has identified a biological link between social isolation and health.

The Importance of Social Connections

Humanity evolved in communities, where social bonds were essential for survival, resource allocation, safety, and social status. Studies have shown that even today, connections with family and friends are crucial for mental and physical well-being. However, in modern society, even residents of large cities often experience social isolation and a lack of meaningful interaction. A 2021 study revealed that one in three adults globally experiences loneliness.

Social isolation and loneliness are on the rise. The World Health Organization (WHO) has declared this issue a global public health challenge. Factors such as urbanization, remote work, and aging populations exacerbate these problems, costing the global economy billions through healthcare expenses and lost productivity. Loneliness shortens life expectancy and reduces healthy years of life.

A Move Forward

Scientists analyzed proteomes—sets of proteins—from blood samples of over 42,000 adults aged 40–69, collected by the UK Biobank. Social isolation was objectively measured based on living conditions and frequency of social activity, while loneliness was assessed subjectively, based on individuals’ feelings.

The researchers identified 175 proteins associated with social isolation and 26 linked to loneliness, with overlap between the two groups. Many of these proteins are produced in response to inflammation, viral infections, and during immune responses. Additionally, these proteins are linked to cardiovascular diseases, type 2 diabetes, stroke, and premature death.

Social Connections at the Cellular Level

For instance, the protein adrenomedullin (ADM), elevated in lonely individuals, plays a role in regulating stress and social hormones such as oxytocin—the “love hormone.” Oxytocin promotes feelings of satisfaction, closeness, and reduced anxiety. Elevated ADM levels are associated with reduced volumes in brain regions responsible for emotional regulation and an increased risk of premature death.

Another protein, ASGR1, which rises due to social isolation, contributes to higher cholesterol levels and an increased risk of cardiovascular diseases. Other identified proteins are similarly implicated in cardiovascular diseases, a greater risk of stroke, and mortality.

Conclusions

According to Professor Jianfeng Feng of Fudan University, a corresponding author of the study, the human body contains over 100,000 proteins with numerous variations.

The authors highlight that studying the physiology of social relationships is timely and holds vast potential for public health, given the growing number of people experiencing loneliness.

Professor Barbara Sahakian from the Department of Psychiatry at the University of Cambridge notes that their findings underscore the critical importance of social connections for human health.