Loneliness linked to dementia risk in large-scale analysis

Feeling lonely increases the risk for dementia by 31%, according to an analysis of data from multiple NIA-funded population-based studies. These findings were focused explicitly on loneliness and looked at its links to Alzheimer's disease, vascular dementia, and cognitive impairment without dementia. The research was funded by NIA and published in Nature Mental Health.

This study analyzed data from more than 600,000 participants across 21 longitudinal cohorts, making it an especially comprehensive investigation into the impact of loneliness on cognitive function. It found that loneliness increased the risk for dementia at a magnitude similar to the impact of being physically inactive or smoking. Specifically, loneliness increased the risk for Alzheimer's by 14%, vascular dementia by 17%, and cognitive impairment by 12%. These findings were consistent even after controlling for factors such as depression and social isolation, underscoring loneliness as an independent risk factor.

Loneliness is the distressing feeling of having fewer or lower quality social interactions or connections than one desires. It is different than social isolation, which is the lack of social contacts and having few people with whom to regularly interact. People can live alone and not feel isolated, and conversely can feel lonely while being with others. Loneliness and social isolation are known to pose health risks in older adults.

Led by researchers at Florida State University, the scientific team performed its large-scale analysis to address three questions: 1) Is loneliness related to increased risk of all-cause dementia? 2) Is loneliness related to increased risk of specific dementias - Alzheimer's and vascular dementia? And 3) Is loneliness related to cognitive impairment? In addition to collating across 13 published studies, the scientists also completed new analyses by coordinating across studies from the NIA-funded Gateway to Global Aging Data that included loneliness and assessments of cognitive status.

The authors of the study suggested this work confirms the association between loneliness and risk of dementia. However, they note as a limitation that the number of selected studies is still small, especially for Alzheimer's and vascular dementia. They proposed that future studies should include better distinction between mild-to-severe cognitive impairment not caused by dementia. Additionally, they suggested that identifying the types and sources of loneliness would be an important way to develop interventions.

This research was supported in part by NIA grants R01AG074573, RF1AG053297, and R01AG068093.

NIA leads NIH's systematic planning, development, and implementation of research milestones to achieve the goal of effectively treating and preventing Alzheimer's and related dementias. This research is related to Milestones:

• 1.F, "Support the inclusion of measures of AD-related phenotypes and environmental exposures in non-AD cohorts to enable new discovery research and to accelerate cross-validation of discoveries made in AD cohorts."
• 2.J, "Expand research on the role of social and psychosocial factors on AD risk and resilience to risk in ethnically and socioeconomically diverse populations to interrogate mechanisms of disparities in health burden of AD, and inform intervention strategies and public health policy. These efforts should utilize a life-course approach."

Reference: Luchetti M, et al. A meta-analysis of loneliness and risk of dementia using longitudinal data from >600,000 individuals. Nature Mental Health. 2024;2:1350-1361. doi: 10.1038/s44220-024-00328-9.