The team found that cognitive performance worsened for older adults on days that they felt lonelier than usual as well as on the following day. They also found that when cognitive performance declined, loneliness increased a short time later. However, experiences of loneliness over the course of a single day did not relate to changes in cognitive performance.

Their findings were published in The Journals of Gerontology Series B.

“These results suggest there may be a vicious cycle between loneliness and cognitive decline over the short term,” said Jee eun Kang, postdoctoral scholar in the Penn State Center for Healthy Aging and lead author of this study. “Loneliness one day may decrease cognitive performance the next day. Then, experiencing decreased cognitive performance can lead to increased loneliness a few hours later, which may create the long-term relationship between cognitive decline and loneliness.”

The researchers studied data from 313 adults in the Einstein Aging Study collected between 2017 and 2020. Participants were between 70 and 90 years of age and lived in the Bronx, New York City, in the community rather than in eldercare facilities. Each participant recorded their momentary feelings of loneliness and completed cognitive tests on a smart phone five times a day for 14 days. Their daily scores of loneliness and cognitive performance were averaged across all measurements taken throughout the day.

“This type of data — where people use cellphones to report their experiences and feelings during the course of their daily lives — provides a rich way to understand people’s natural day-to-day experience,” said Martin Sliwinski, professor of human development and family studies, director of the Center for Healthy Aging and senior author of the study. “If participants had come into a laboratory, their social contact and thoughts would be affected in ways that could influence their loneliness or cognitive performance, either positively or negatively.”

Although the size of the relationships between loneliness and cognitive decline measured from one day to the next or within a single day were small, the researchers said that is to be expected.

“These results suggest that those tiny differences in loneliness or mental ability may add up,” said Jennifer Graham-Engeland, professor of biobehavioral health, associate director of the Center for Healthy Aging and co-author of this study.

Some researchers have proposed that loneliness may be an evolutionary cue intended to motivate humans to repair or replace their social relationships, according to the researchers. When people experience loneliness, it may act as a stressor, explaining the association with decreased cognitive performance.

“Our data suggest that when older adults do not feel sharp, they may avoid social contact — but that could worsen the problem,” Kang said. “If older adults feel lonely, they should take action early to prevent chronic loneliness. For example, they could reach out to a friend or neighbor or even just make small talk with people they encounter that day.”

Meanwhile, younger people can help by reaching out to older adults on a regular basis, according to Kang.

“Loneliness is dynamic, not stable,” she said. “Your grandma may not be a lonely person, but — like most people — she probably feels lonely sometimes. Anytime you reach out to older adults and engage with them, you are supporting their cognitive and emotional health that day and over the course of their lives.”

The researchers noted that this study is aligned with the priorities of the Penn State Social Science Research Institute’s Geroscience and Dementia Prevention Consortium, which Sliwinski directs.

“In the consortium, we seek to understand how modifiable risk factors like loneliness contribute to cognitive decline and neurodegeneration,” Sliwinski said. “This study is one of many at Penn State aiming to help older adults retain their cognitive function.”

Lynn Martire, professor of human development and family studies, and David Almeida, professor of human development and family studies, also contributed to this research.

The National Institutes of Health funded this study.