Study finds loneliness increases dementia risk later in life

Scottish researchers  discovered a direct causal effect between social isolation and a faster decline in cognitive function as we grow older.

Pathological cognitive decline is most often driven by Alzheimer’s and related dementias, say scientists.

The University of St Andrews-led study 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 organizations, 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, researchers say they appear to have independent effects on cognitive function. 

St Andrews researchers, alongside colleagues from the Max Planck Institute for Demographic Research in Germany and Emory University in the US, analyzed data from the US Health and Retirement study, looking at 137,653 cognitive function tests taken between 2004 and 2018 by more than 30 000 people.  

The findings, published in The Journals of Gerontology, Series B: Psychological Sciences and Social Sciences, showed that reducing social isolation has a "protective" effect on cognitive function for all groups regardless of gender, race, ethnicity and educational level with only minor differences among social categories.  

There has been a lot of recent interest in the health effects of social isolation and loneliness, especially focused on teenagers and older adults.

Prior to COVID-19, around one-in-four people aged 65 and over identified as being socially isolated, triggering concerns about the health implications.

Loneliness has been recognized as a major public health issue in high income countries including the UK, United States, Australia, Germany, Japan and Sweden.

Alzheimer’s disease, which has no known cure already afflicts an estimated 6.9 million people in the United States alone, with around one in every 11 over 65s effected in the UK.

Study lead author 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."

Dr. Hale added: "As Alzheimer’s is a leading cause of death for older adults in the UK and US, constructing the scaffolding to allow for regular social interaction, especially for those who may not have family or friends nearby, should be a public health priority.”