Measuring Loneliness at an Unprecedented Scale: The INTERACT Study’s Approach and Initial Findings

Background Loneliness is increasingly recognised as a major public health challenge with significant implications for mental, physical and social wellbeing. Despite growing interest, population-level data remains limited, particularly at the intersection of individual, community and geographic determinants. The Measuring Loneliness in the UK (INTERACT) Study was designed to map the prevalence, intensity and sociodemographic determinants of loneliness across diverse population groups in the UK. The aim of this first paper in a series is to describe the development, implementation and early findings of the INTERACT Survey, which to date is the largest population-based study of loneliness, social isolation and social capital conducted in the UK. Methods Between March and July 2023, 135,725 adults completed the online INTERACT Survey. The instrument included validated measures of loneliness (UCLA-3 & ONS Direct Measure), social capital indicators and demographic variables. Descriptive statistics were stratified by key subgroups. A novel geospatial analysis at Lower Super Output Area (LSOA) level was used to visualise clustering of loneliness across the UK. Results Loneliness was widespread, with 16.5% of participants reporting they often or always felt lonely. Younger adults, individuals from minority ethnic backgrounds, those who were single or unemployed and people with disabilities were more likely to report frequent loneliness. Social capital varied widely, with lower scores in urban areas and among groups with greater reported loneliness. The COVID-19 pandemic was reported as an amplifying factor, with 44% of respondents indicating increased loneliness during the pandemic. Geospatial mapping revealed distinct loneliness “hotspots” in densely populated urban regions, particularly London, Birmingham and Manchester. Conclusions The INTERACT Study provides a comprehensive national dataset on loneliness and social disconnection in the UK. Its scale, methodological rigour and spatial granularity offer valuable insight for designing targeted, place-based interventions. Future papers will present inferential analyses, explore lived experience and propose policy-relevant solutions to mitigate loneliness and promote social connection across communities.