Impact of Environmental Exposure on Infant Sleep : The Exposome Approach.

Sleep is fundamental for infant development and health, playing a critical role in cognitive, socio-emotional, and physical growth. However, environmental factors can impact the quality and duration of sleep in infants. This review synthesises current evidence on the associations between environmental chemical exposures and infant sleep outcomes, with a focus on the first 1000 days of life. Infants may be exposed to environmental pollutants before birth, through the placenta, or after birth, via breastfeeding, diet, and external sources such as inhalation, dust contact, or hand-to-mouth exposure. Given their ongoing development, foetuses and infants are particularly vulnerable to these pollutants. This period of rapid growth and maturation represents a highly sensitive window for environmental exposures. This review covers various categories of environmental pollutants, including persistent organic pollutants (PCBs, dioxins), non-persistent pollutants (phthalates, BPA), air pollutants (particulate matter, second-hand smoke), and water contaminants (nitrates, microplastics). Environmental chemicals exposure could be assessed using parental questionnaires or biological monitoring, while sleep is evaluated using actigraphy, polysomnography, or parental reporting. Some evidence suggests that both prenatal and postnatal exposure to environmental contaminants may be associated with sleep disturbances in children, particularly in girls. Despite the numerous studies on adults and the mechanisms associated with these pollutants (neurotoxicity, endocrine disruption), which suggest an effect on sleep, there is a lack of studies in children, resulting in limited associations in the literature. Therefore, it is imperative to conduct studies on environmental pollutants present in breast milk, diet, and/or ambient air to understand their impact on infant sleep.