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.
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."
Dr. Jo Hale, Study Lead Author, University of St Andrews
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