The Lonely Brain: Loneliness and Brain Health in Midlife and Older Age

Loneliness represents a prominent population-health issue: More than nine million adults in the UK report that they often or always feel lonely, and 4 out of 10 Norwegians report feeling lonely in their daily life. Epidemiological studies show that loneliness relates to brain health, and that it can double the risk for Alzheimer's disease. Adults over 80 are twice as likely to feel lonely than younger adults. With older age, one is more susceptible to risk factors such as loss of partner and living alone, and most campaigns to reduce loneliness focus on increasing social activity in the ageing population. However, studies also show that loneliness can lead to decline in brain health regardless of how socially active one is, and many can relate to being contented when alone while feeling lonely in a crowd. Hence, there are important conceptual distinctions between objective social isolation, such as living alone, and subjective loneliness, which refers to a sense of lacking desired social contact and belongingness. Loneliness is also a major risk factor for depression, and while the prevalence of loneliness varies with age, the association between loneliness and depression remains stable across the lifespan. This project aims to investigate what it is that makes people feel lonely, and how loneliness relates to brain health in midlife and older age. By using large international datasets, the study will address the following research questions: I) How do factors that are intrinsic to the individual, such as personality traits, and external factors, such as social isolation, contribute to loneliness? II) To what extent do these factors represent risk for decline in brain health? By increasing the understanding of what it is that makes people vulnerable to loneliness and decline in brain health, the project will contribute to improving preventive interventions and promoting mental health in the general population.

The mobility grant has provided excellent opportunities for establishing an international, interdisciplinary team including researchers in Oxford, Oslo, and beyond. During the project period, the project leader contributed to a number of studies applying computational tools to neuroimaging data, and was awarded a prestigious grant from the Swiss National Science Foundation. The published results from the project period contribute to developing and validating biomarkers for brain health and disease. Work that is currently under review (published as preprint) contribute to identifying groups of individuals who are vulnerable to loneliness and associated health problems, and underline the need for public-health initiatives addressing socioeconomic conditions as well as social, mental, and physical health to reduce the risk of loneliness and adverse health outcomes in the population.

Both loneliness and degenerative brain changes are prevalent problems that increase with age. Epidemiological data suggest that these phenomena are related, as loneliness has been shown to double the risk for Alzheimer's disease. The pertinent questions are: What is it that makes people feel lonely, and to what extent do these factors relate to brain health or serve as risk factors for neural decline? By including large cross-sectional and longitudinal datasets across the UK and Norway, this study aims to address the following research questions: I) How do factors that are more intrinsic to the individual, such as the personality trait neuroticism, and external factors, such as objective, social isolation, contribute to loneliness? II) To what extent do these factors relate to brain health, or serve as risk factors for neural decline? Brain structure will be measured by white matter microstructure, volume, and cortical thickness. Statistical analysis and big-data handling will be performed using the ROOT framework, a data analysis package developed at CERN, in addition to Python, Matlab and the FSL and FreeSurfer software for neuroimaging analyses. The study is expected to have high impact on society, as loneliness represents a prominent population-health issue: More than nine million adults in the UK report that they often or always feel lonely. According to Statistics Norway, 4 out of 10 Norwegians report feeling lonely in their daily life. The study will contribute to identifying groups of individuals who are vulnerable to loneliness, poorer brain health or accelerated decline in brain structure. As such, it will have implications on an individual, community, and global level, by promoting mental health and wellbeing, improving preventive interventions, and reducing health care costs.