The human heart in conflict with itself and the loneliness of the soul have served as inspiration for various forms of artistic expression throughout the ages. Regarding the latter condition, in popular music a top song in 1969 by the group Three Dog Night was titled, “One Is The Loneliest Number.” That particular numeral posits that an aspect of loneliness is a subjective feeling of being isolated and alone. In a related vein, social isolation is an objective state of having few relationships or infrequent contact with others. Meanwhile, along with many other nations, the United States is undergoing a profound demographic shift in which the size of the population 65 years of age and older, both numerically and proportionately, is increasing at a more accelerated rate than it is for younger age groups.
The National Academies of Science, Engineering, and Medicine published a report in 2020 on social isolation and loneliness among older adults, indicating that approximately 24% of community-dwelling Americans aged 65 and older are considered to be socially isolated. A significant proportion of adults in this country report feeling lonely, that is, 35% aged 45 and older and 43% aged 60 and older. Current evidence suggests that many older adults are socially isolated or lonely (or both) in ways that place their health at risk. Moreover, social isolation significantly increases an individual’s risk of mortality from all causes, a risk that may rival the risks of smoking, obesity, and lack of suitable physical activity. Additionally, loneliness has been associated with higher rates of clinically significant depression, anxiety, suicidal ideation, a 59% increased risk of functional decline, and a 45% increased risk of death. Poor social relationships (characterized by social isolation or loneliness) also have been associated with a 29% increased risk of incident coronary heart disease and a 32% increased risk of stroke.
While acknowledging that loneliness is associated with increased morbidity and mortality, an article published in the October 2021 issue of the journal Neuropsychopharmacology indicates that a deeper understanding of the neurobiological mechanisms that underly loneliness is needed to identify potential intervention targets. Identifying such mechanisms is critical for understanding how loneliness contributes to poor mental and physical health, and for conceptualizing potential pharmacological and neurostimulation targets. This first systemic review of the neurobiology of loneliness shows that despite some mixed evidence, the condition is associated with structural and functional differences in the prefrontal cortex, insula, hippocampus, amygdala, and posterior superior temporal cortex, as well as attentional and visual networks.
Apart from the impact on patients, loneliness also can have a major effect on the health care delivery system as measured by an increased use of inpatient care, more visits to providers, increased re-hospitalizations, and longer lengths of stay. A challenge for providers is to develop effective methods to identify social isolation and loneliness in health care settings and use the findings to target appropriate clinical and public health interventions to individual patients, and to target high-need regions and populations served by a practice or health care system.