"Where are all the lonely people?" A population-based study of high-risk groups across the life span

Loneliness is a prevalent and urgent public health issue. Optimal planning of community approaches to loneliness requires a differentiated understanding of loneliness across the life span. We identified groups at high risk of loneliness by exploring the relationship between loneliness and socio-demographic and health-related factors across multiple age groups. This was a combined population-based questionnaire survey and register data study based on a representative sample, including 33,285 Danish individuals aged 16-102 years. Loneliness was measured using the Three-Item Loneliness Scale. The relation between loneliness and age took a shallow U-shaped distribution. Ethnic minority status, receiving disability pensions or being unemployed, living alone, prolonged mental disorder, and psychiatric treatment were strongly associated with severe loneliness. Socio-demographic and health-related factors were associated with an increased risk of severe loneliness in specific age groups. Being female, having a low educational level and living in a deprived area were only associated with loneliness in adolescence/emerging adulthood. Receiving disability pensions and living alone (i.e., divorced), on the other hand, were strongly associated with loneliness in early and middle adulthood and young-old age. Ethnic minority status, living alone, and prolonged mental disorder may well be key factors in determining the generic level of loneliness in a given population. Other conditions are associated with an increased risk of severe loneliness in specific age groups and may moderate the age-loneliness relation. These findings may help to identify populations within communities at risk of loneliness and thereby support the implementation of policies and public health interventions across the life span.