Susan Charles, associate dean of graduate programs in the School of Social Ecology at the University of California, Irvine, has been awarded a $2,550,958 grant from the National Institute on Aging.
The grant will fund Charles's project, “Linking Daily Dynamics of Social Connection to Physical and Cognitive Functioning,” which aims to investigate how the daily fluctuations of feeling socially connected or disconnected shape long-term physical and mental health. This research seeks to change how loneliness and social isolation are addressed by doctors, therapists, and public health officials.
While decades of research confirm the health benefits of close relationships, Charles argues that previous scientific understanding has been limited by viewing social connection as a fixed trait. She notes that social connection varies daily, similar to other emotional experiences. This means a person feeling connected on one day might feel isolated on another.
Charles believes these daily fluctuations are key to understanding how social life affects health. She illustrates this by pointing to ordinary decisions, such as calling a friend or attending a social function despite being tired. These, she says, may not seem like health decisions but significantly influence well-being. The effects are both immediate, like a shared laugh easing distress, and cumulative. For example, regular neighbor dinners promote physical activity and mental engagement, like tracking information and retrieving memories. Charles states that "consistent positive social connection enhance health, affecting myriad health outcomes from physical symptoms to gene expression."
To test these ideas, Charles's team will utilize the Midlife in the United States study (MIDUS), a comprehensive longitudinal dataset. The project will draw on two longitudinal daily diary datasets spanning nearly 20 years. One dataset includes participants who completed nightly phone interviews for a week across three waves in 2002, 2014, and 2023. A second dataset captures two waves of daily diary data, beginning in 2012 and 2023, spanning about a decade.
Together, the study tracks over 2,900 adults, with ages ranging from 24 to 97. In addition to the daily diary interviews, participants underwent extensive surveys, cognitive assessments, and some provided biological samples and completed physical fitness tasks. Charles noted that examining these different facets together provides an unprecedented view into how daily lives unfold and relate to various measures of cognitive, physical, and mental health.
The research team plans to examine biological markers such as cortisol, known as the “stress hormone,” which is linked to cognitive decline and poor physical health when levels are chronically high. They will also analyze inflammatory markers, gene expression profiles, and biomarkers related to biological age acceleration, which measure how quickly a person’s cells are aging compared to their chronological age.
Charles hopes to connect the social world to a phenomenon called “inflammaging,” an age-related increase in chronic low-grade inflammation that contributes to conditions like cardiovascular disease, diabetes, certain dementias, and arthritis. The team will examine biomarkers related to poorer health—including chronic inflammation, high cortisol levels, and gene expression associated with inflammation and viral load—and study their relationship to the consistency and levels of daily social connection.
If daily patterns of social connection can be shown to influence these biological markers, the implications for preventive medicine could be substantial. The study's broad age range, from young adults to nonagenarians, allows for an examination of how the relationship between social connection and health changes as the body becomes more vulnerable. Charles emphasized that while social connections are vital for all ages, the study is particularly interested in how these patterns change in later life and how their relationship with health may vary in individuals with less robust physical systems.
Amidst the United States Surgeon General's declaration of loneliness as a public health epidemic, Charles views her study as a way to reframe the conversation. Instead of merely warning about the risks of social isolation, she aims to acknowledge the power of positive social connections and identify the specific contexts and circumstances under which they enhance health. Her goal is simple yet potentially transformative: to ensure that "social connection should be listed as a daily health behavior for everyone."
