by Jake Hawkes, University College London

Credit: CC0 Public Domain

People over 55 who live alone are 30% more likely to develop dementia than those who live with others, according to a new UCL-led study.

The systematic review and meta-analysis, published in Ageing Research Reviews, suggests that social isolation could be a greater risk factor for dementia than previously believed.

Lead author Dr. Roopal Desai (UCL Psychology & Language Sciences) said: "More and more people are living alone, particularly older people, and some studies have also suggested that increasing numbers of people are experiencing loneliness in countries such as the UK. Our findings suggest that low social contact could have serious implications for dementia rates, especially as dementia rates are already rising due to aging populations."

The research team reviewed evidence from 12 studies in seven countries in Europe and Asia, which pulled together data from 21,666 people aged over 55. They used living alone as a proxy measure for social isolation, which can be difficult to quantify.

While only three of the studies had found that living alone was significantly associated with increased risk of dementia, by combining the results from the 12 studies the researchers were able to increase the power of the analysis. As a result they were better able to detect the effect of living alone and subsequent risk of dementia, concluding there was a significant link between the two.

A landmark study published in 2017, led by Professor Gill Livingston (UCL Psychiatry), had previously calculated that if social isolation could be eliminated entirely, then dementia cases could be reduced by 5.9%. This study updates that figure to 8.9%, when using living alone as a proxy measure for social isolation, suggesting that social isolation could be a larger contributor to dementia risk across the population than physical inactivity, hypertension, diabetes or obesity.

Dr. Desai said: "This study doesn't explain why living alone is a risk factor for dementia but there are several plausible explanations. It might be because people who live alone experience more loneliness or more stress, both of which can have adverse physical health effects, or it may be due to a lack of cognitive stimulation which is needed to maintain neural connections."

The research team did not study the reasons for living alone, so it's possible that the dementia risk may have been influenced by other factors such as bereavement among those who have been widowed.

The researchers say that identifying lifestyle factors that affect dementia risk is not only important for prevention, but also for dementia care, as evidence suggests that even after people begin experiencing dementia symptoms, lifestyle changes can still slow the rate of cognitive decline.

Senior author Dr. Georgina Charlesworth (UCL Psychology & Language Sciences) said:

"During the COVID-19 pandemic, self-isolating has been vital to reduce the spread of the virus. The pandemic has raised awareness of how difficult it can be, practically and emotionally, to live alone when it has not been our choice to do so. Finding ways to keep cognitively, socially and physically active is important for our wellbeing, and to reduce dementia risk. Strategies such as social prescribing, where health professionals refer people to community groups, have been disrupted in recent months, with increasing reliance on activities delivered over the internet. While we don't know if internet-delivered social interventions would effectively reduce dementia risk—as we would need further research to confirm that—they can certainly be helpful to support people's wellbeing for those on the 'right-side' of the digital divide. We need policies that ensure that those without access to the Internet are not 'digitally-isolated.'"

Fiona Carragher, Director of Research and Influencing at Alzheimer's Society which funded this study said: "We've known for some time that lack of social contact can play a role in our risk of developing dementia later in life. At a time where people have been socially isolated during the pandemic, this research, funded by Alzheimer's Society brings this potential risk into sharper focus. Research like this is critical to understanding how we may be able to reduce the risk of developing dementia later in life, but we must remember that dementia is complex, and there are many factors involved in developing the condition. There are steps we can take now to reduce our risk like keeping ourselves physically, mentally and socially active while maintaining a healthy, balanced diet and avoiding smoking. The coronavirus has hit the finances of UK charities like Alzheimer's Society hard which has a knock on effect for research like this. With an expected 40% average fall in investment this year across medical research charities, we are calling for emergency financial support from the Government to continue our life-changing work."

More information: Roopal Desai et al. Living alone and risk of dementia: A systematic review and meta-analysis, Ageing Research Reviews (2020). DOI: 10.1016/j.arr.2020.101122

Provided by University College London