ABSTRACT

Background 

Living in compact neighbourhoods that are walkable, well connected, have accessible green space and good access to amenities and public transport can bring benefits for physical and mental health. The Scottish Government is promoting the development of ’20-minute neighbourhoods’ in Scotland. These are neighbourhoods with easily accessible facilities within walking distance of homes. However, the Covid-19 pandemic has raised concern that the higher dwelling density needed to sustain 20-minute neighbourhoods could contribute to transmission of Covid-19 and other respiratory infections. Studies of population density and Covid-19 transmission have reached contradictory results and have often studied population density at large spatial scales. A better understanding of the links between respiratory viral transmission and population density and other aspects of neighbourhood design is needed to inform the development of Scottish planning policy. 

Objectives

We aimed to identify, appraise and synthesise available evidence on links between transmission of respiratory viruses, including Covid-19, and dwelling or population density and other features of neighbourhood design. We restricted our review to quantitative empirical studies considering these characteristics at neighbourhood, sub-city or city level.

Methods

We conducted comprehensive, systematic electronic searches in six English and two Chinese databases to identify studies, up to 15th October 2020, which assessed the association between transmission of Covid-19 or other respiratory viruses, and population density and/or other features of neighbourhood characteristics. We supplemented this by reviewing reference lists and forward citation tracking. After titles, abstracts and subsequent full text screening, all eligible studies were quality assessed and given a GRADE level. The high level of heterogeneity of the studies did not allow for statistical analysis and therefore narrative analysis was employed to summarise findings.

Results

Database searches identified 1884 papers after de-duplication, and a further 6 through citation tracking. Of those, 21 papers met the inclusion criteria and were reviewed. Most studies reported evidence from USA or China, with one from Israel and one from the UK. The quality of the studies was low (n=5) or very low (n=16). Fifteen papers studied associations with Covid-19; six considered other respiratory infections. Most were ecological studies. Adjustment for confounding variables ranged from possible over control to no adjustment at all. There was inconsistency in primary and secondary outcomes. Twenty studies analysed links with population density, one of which also considered housing density. These reported conflicting findings relating to population and housing density. Thirteen suggested a positive association between transmission and density, seven a negative association but several of these were not statistically significant, and the quality of the studies means overall findings should be treated with extreme caution. The studies considered a range of other neighbourhood characteristics including walkability; land use mix; building scale and other housing features; density of or distance to schools and other services; and markers of urban quality. Only a small number of studies investigated each of these, using differing measures, and their findings were inconsistent.

Conclusions

This review found no convincing evidence of a link between population density and transmission of Covid-19 and other respiratory infections. Although the possibility of an association cannot be ruled out, the current evidence does not suggest a need to change the current Scottish Government policy of support for the ‘20-minute neighbourhood’ concept. Similarly, no clear conclusion can be drawn about any association between other characteristics of neighbourhood design and transmission of respiratory infection, including Covid-19. Further multi-disciplinary research using appropriate, sophisticated designs, is needed to allow a better understanding of links between neighbourhood characteristics and transmission of respiratory infections.

https://www.ed.ac.uk/files/atoms/files/uncover_025-01_-_review_-_neighbourhood_design_0