Could a smaller social circle be the key to longevity?
Research shows that many animals, including humans, tend to withdraw as they age, a behavioral pattern known as social aging — and isolation seems to have an evolutionary advantage.
A new study from the University of Exeter’s Centre for Research in Animal Behavior found that our closest primate relatives are less likely to get sick when they limit social interaction.
The research team analyzed a group of adult female rhesus macaques to better understand the relationship between aging, sociability, and illness. Using social network models, they measured “social centrality,” an aggregate of total social partners and time spent socializing.
They combined their data on social centrality with a simulation model for infectious disease to determine if reduced connectivity could decrease infection risk, specifically under conditions that mimicked age-related declines in immunity.
Researchers found that older macaques with limited social interaction reduced their risk of catching an infectious disease from within the group, demonstrating a “protective effect” of aging.
Study co-author Erin Siracusa, a researcher from the University of Exeter’s Centre for Research in Animal Behavior, notes, “Our findings suggest a powerful reason why many animals, including humans, might reduce their social connections as they age.”
Immunity is weakened in older adults, increasing the risk of contracting an infectious disease. Yet, the macaques study found that older macaques had lower infection rates than their younger counterparts.
“This cost-benefit ratio can change across individuals’ lifespans, which may drive changes in social behavior,” says Siracusa. “Older individuals may be more susceptible to diseases — but once we accounted for that in our data, we found that older macaques suffered lower infection costs than their younger counterparts.”
Study authors note that their results operate on the assumption that infection risk increases with interaction time, but some infections require only a very brief interaction to spread.
The tendency to withdraw is mirrored in the human population.
A 2022 poll of 2,000 Americans aged 55 and older found that 75% of the aging population admitted their social circle has shrunk as they’ve gotten older, and nearly half of respondents (48%) shared that they’ve stopped being friends with at least three people in the last two years.
While smaller social circles may prevent illness, isolation is associated with myriad health problems. The World Health Organization has declared loneliness a “pressing health threat,” with risks as deadly as smoking up to 15 cigarettes a day.
Studies have shown that perennially being by oneself carries the risk of anxiety, depression, poor immune function, cardiovascular issues, and even brain shrinkage.
Thus, limiting but not eliminating social interaction seems to be the sweet spot for survival.
