Associations of neighbourhood housing density with loneliness and social isolation: a cross-sectional study using UK Biobank data

Abstract

<h3>Background</h3><p>With increasing urbanisation, the role of urban density on mental wellbeing has gained importance. However, the evidence linking housing density, a fundamental attribute of urban built environment, with loneliness and social isolation has been scarce. We examined associations of neighbourhood housing density with loneliness and social isolation in a UK-wide cohort by using the high-resolution UK Biobank Urban Morphometric Platform (known as UKBUMP) database created by our team.</p><h3>Methods</h3><p>We leveraged data from UK Biobank, a cohort of adult participants aged 37–73 years recruited between 2006 and 2010. Neighbourhood housing unit density was objectively measured within a walkable scale of 1km and 2km street catchments of participant's geocoded dwelling (equivalent to approximately a 10-min and 20-min walk). Other built environment factors, including density of public transport, traffic intensity of the nearest street, terrain variability, street-level physical walkability, and greenspace, were also modelled. A series of logistic regression models examined the associations of housing density with loneliness and social isolation after rigorous adjustments for built environment and sociodemographic covariates. Restricted cubic spline models were used to examine non-linear associations. We stratified analyses by sex and age. Ethical approval was received by the UK Biobank from the National Health Service National Research Ethics Service and data access for the study was approved by the UK Biobank Scientific Committee.</p><h3>Findings</h3><p>Our study comprised 478 265 participants (260 641 [54·5%] of whom were women) with complete data on either outcome and housing density. 281 418 and 291 190 participants remained after full adjustment in models of loneliness and social isolation, respectively. Each 1000 units per km² increment in housing density within a 1 km residential street catchment was independently associated with an increase of 3·7% (OR 1·037 [95% CI 1·02–1·05], p<0·0001) and 17·4% (1·174 [1·16–1·19], p<0·0001) in odds of loneliness and social isolation after full adjustment. The results remained consistent for a catchment of 2km. A non-linear dose-response was observed. The association between housing density and loneliness was more pronounced among participants aged 50–59 years (participants aged <50 years: OR 1·108 [95% CI 0·97–1.26], p=0·1171; 50–59 years: 1·188 [1·06–1·33], p=0·0023; ≥60 years: 1·114 [0·99–1·25], p=0·0646 for the highest housing density quartile <em>vs</em> the lowest; p_interaction=0.0171) and among men (men: 1·235 [1·12–1·36], p<0·0001; women: 1·051 [0·96–1·16], p=0·3054 for the highest exposure quartile <em>vs</em> the lowest; p_interaction<0·0001). Limitations included the cross-sectional study design, non-representativeness of the UK Biobank base population, and potential residual confounding.</p><h3>Interpretation</h3><p>In a UK-wide study, we found that increased neighbourhood housing density was associated with increased odds of loneliness and social isolation. High density environments might exacerbate unwanted social contacts, resulting in higher social stress and reduced social connections. With more than 65% of the global population projected to reside in urban areas by 2050, strategic city planning achieved by optimising residential density might constitute a population-wide preventive approach for reducing burdens of loneliness and social isolation.</p>