The study, led by the University of California, Davis, used advanced statistical modeling to chart loneliness and social isolation as older adults move through stages of cognitive impairment and mortality. The results suggest that loneliness plays a much stronger role in cognitive impairment and shorter life spans than social isolation on its own.
"Loneliness is a perception," said Tomiko Yoneda, an assistant professor of psychology at UC Davis and the study's lead author. "You could be surrounded by a crowd of people and still feel lonely, whereas isolation is just being alone. Some people might be not lonely at all and be completely content in their solitude."
The study was published in the Journal of Personality and Social Psychology on June 15.
Modeling people's lifetimes
The team's statistical models tested the impacts of loneliness and social isolation, both together and separately, on transitions between various states of cognitive impairment to the end of people's lives.
"This approach is crucial," said Yoneda, "because cognitive impairment increases mortality risk, and both risks increase with age."
Yoneda led the team of 24 researchers who analyzed data from 175,000 participants over the age of 50. Participants reported how frequently they felt lonely as well as how often they had contact with others.
The analysis found that loneliness was consistently associated with a higher risk of cognitive impairment and a shorter life, even after taking social isolation into account. Social isolation on its own was not consistently associated with cognitive decline and had only a weak association with a shorter life.
A 10% increase in reports of feeling lonely was associated with an 8%-9% increased risk of severely impaired cognitive function and of transitioning from no impairment to mildly impaired cognitive function.
Reporting loneliness more frequently was also associated with a 3% lower likelihood of returning from mild cognitive impairment to no impairment. This suggest, researchers said, that alleviating loneliness may be important for recovery. Higher loneliness was the most consistent risk earlier in life even before measurable cognitive decline appeared, researchers said.
"Loneliness may be most prominent in early stages of cognitive impairment, but is also a risk factor after impairment develops," said the study's supervising author Eileen K. Graham , an associate professor of medical social sciences at Northwestern University. "Lonelier individuals may be more likely to progress to more severe stages and less likely to recover."
Reducing loneliness
The researchers said that finding ways to reduce loneliness, which would blunt its effects on cognitive impairment, could reduce the costs associated with care for individuals with dementia and other cognitive ailments.
They also said that individuals worried about cognitive decline can make efforts to strengthen their social connections with the people around them. For instance, hospitals and care organizations can incorporate screening tools that identify loneliness. Communities could create opportunities for older adults to engage with others and build a sense of belonging.
Additional co-authors include Emorie Beck, assistant professor of psychology at UC Davis; as well as researchers representing the University of Southern California, Auburn University, UC Riverside, University College London, Western Virginia University, University of Limerick, Rush University Medical Center, Ohio University Heritage College of Osteopathic Medicine and Cornell University.
The study was funded by the National Institutes of Health.
