Summary: Social isolation has a direct causal impact on how quickly cognitive function declines in later life, independent of whether someone feels lonely. By analyzing more than 137,000 cognitive tests from over 30,000 older adults, the study found that reduced social contact consistently predicted faster decline across every demographic group.
Loneliness and isolation each influence health, but only isolation reliably caused cognitive deterioration. With rates of Alzheimer’s already high and no cure available, the findings highlight that strengthening social connection is not only emotionally beneficial but neurologically protective.
Key Facts:
- Isolation as a Cause: Objective social isolation—not just loneliness—directly accelerates cognitive decline.
- Consistent Across Groups: The effect appeared across gender, race, ethnicity, and education levels.
- Large-Scale Evidence: Findings were based on over 137,000 cognitive assessments collected over 14 years.
Source: University of St. Andrews
New research from the University of St Andrews has discovered a direct causal effect between social isolation and a faster decline in later- life cognitive function. Pathological cognitive decline is most often driven by Alzheimer’s and related dementias
The study, published today (16 December 2025) in The Journals of Gerontology, Series B: Psychological Sciences and Social Sciences found a consistent pattern of higher social isolation causing faster cognitive decline whether or not people identify as lonely.
Social isolation is objectively measured as, for example, sociability, membership in community organisations, and religious participation, whereas loneliness is a subjective report of how often people feel lonely.
Whilst social isolation and loneliness are often thought of as associated, they appear to have independent effects on cognitive function.
The School of Geography and Sustainable Development at St Andrews, alongside researchers from the Max Planck Institute for Demographic Research in Germany and Emory University in the US, analysed data from the US Health and Retirement study, looking at 137, 653 cognitive function tests taken between 2004 and 2018 by over 30 000 individuals.
They found that reducing social isolation has a protective effect on cognitive function for all subpopulations regardless of gender, race, ethnicity and educational level with only minor differences among social categories.
There has been a great deal of interest in the health effects of social isolation and loneliness, especially focussed on adolescents and older adults. Prior to Covid 19, about a quarter of older individuals (65 and over) identified as being socially isolated, spurring concerns about health implications. Likewise, loneliness has been recognised as a major public health issue in high income countries including the US, UK, Sweden, Australia, Germany and Japan.
In the US, Alzheimer’s disease already afflicts an estimated 6.9 million people, with around 1 in every 11 of over 65s effected in the UK. With no known cure, prevention is all important.
Lead author of the paper, Dr Jo Hale from the University of St Andrews, said: “Around the holidays, many of us think a lot about how important it is to be surrounded by family and friends. From Pagan winter holidays to classic Christmas tales, we’re reminded that social engagement is good for our mental health.
“This research shows that it’s also important for our cognitive health. As Alzheimer’s is a leading cause of death for older adults in the UK/US, constructing the scaffolding to allow for regular social interaction, especially for those who mayn’t have family or friends nearby, should be a public health priority.”
Key Questions Answered:
A: The study shows a direct causal link: higher isolation predicts faster decline regardless of subjective loneliness.
A: No. Loneliness is subjective and emotional, while isolation is behavioral; only isolation reliably drove cognitive decline.
A: Every subgroup studied—across all demographic lines—showed cognitive protection when isolation was reduced.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this social isolation and cognition research news
Author: Ruth Sanderson
Source: University of St Andrews
Contact: Ruth Sanderson – University of St Andrews
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Disentangling social isolation, loneliness, and later-life function for older adults in the United States: Evidence from causal inference modeling” by Jo Hale et al. The Journals of Gerontology Series B
Abstract
Disentangling social isolation, loneliness, and later-life function for older adults in the United States: Evidence from causal inference modeling
Objectives
Older adults are at high risk of the negative health impacts of social isolation and loneliness. One of those possible negative health impacts is Alzheimer’s disease, a leading cause of death for adults in the United States and many high-income countries.
Taking a life course perspective, we explore whether there is a direct causal effect of social isolation on later-life trajectories of cognitive function, the extent to which any effect of social isolation on cognitive impairment operates indirectly through loneliness, who may be most vulnerable, and the potential efficacy of a statistical intervention for those living alone.
Methods
We use a counterfactual approach, the g-formula, with the U.S. Health and Retirement Study, analyzing data from 30,421 individuals with 137,653 observations across 2004-2018.
Results
We find a consistent pattern of social isolation having a detrimental direct causal effect on cognitive function, with only 6% of this effect operating through loneliness. Reducing social isolation has a protective effect on cognitive function for all subpopulations regardless of gender, race/ethnicity, and educational level, with only minor differences among social categories.
Our statistical intervention shows that targeting social isolation in those living alone may be one viable public health strategy for protecting against cognitive decline.
Discussion
Our results suggest that addressing social isolation—and, by extension, its effects on health—requires both a broad understanding of its heterogenous impacts on the general population and a nuanced approach to targeting public health interventions where they can be most effective.
