Urban environmental exposures during the first 2000 days of life as a foundation for health across the life-course: a scoping review.

Objectives: By 2030, 60% of the global population is expected to live in urban areas. Exposure to urban environments during the first 2000 days of life can have positive or negative health outcomes across the life course. Understanding the types of urban exposures that influence health outcomes is needed to guide research priorities for public health and urban planning. This review aims to summarise the published research examining the health outcomes of all urban environmental exposures during the first 2000 days of life, identify the quantity and characteristics of research in this area, methods used, and knowledge gaps.

Methods: We conducted a scoping review using the JBI methodology for scoping reviews. Eight databases were searched for peer-reviewed primary studies. Inclusion criteria were studies that measured maternal, infant and child exposure to everyday urban environment features and conditions in cities/metropolitan areas during the first 2000 days of life and reported offspring health outcomes across the life course, including embryo, fetal/newborn, infant, child, adolescent, and adult outcomes. We used Covidence software for data screening and extraction. Study characteristics and findings were summarised using tables and narrative synthesis.

Results: We reviewed 235 articles, which included studies conducted across 41 countries, the majority in the US (n = 63). A broad range of environmental exposures were studied, spanning seven categories: air pollution; energy-based pollution; atmosphere, chemical and metal exposure; neighbourhood-built and natural environment features; neighbourhood community conditions; and residential living conditions. Air pollution was the most studied exposure type (n = 153 studies). Health outcomes were reported for all life stages except adults, with fetal/newborn outcomes the most studied life stage (n = 137).

Conclusions: We found that most research investigating urban environmental exposures in the first 2000 days and health outcomes across the life course focused on air pollution exposures and fetal/newborn health outcomes, using correlational retrospective cohort designs. Few studies included multiple environmental exposures. There is a clear need for more longitudinal research to determine the health impacts of multiple urban environmental exposures across the life course. This will assist in developing urban design and planning strategies and population health to mitigate health risks across the life course.