Dark Sleep Environment

Research summary

• Research on night-time light exposure is supported by a large prospective cohort study linking light exposure at night to higher cardiovascular disease incidence, alongside a microlongitudinal study finding night-to-night associations between light exposure and sleep health, and broader reviews on artificial light at night and circadian disruption.
• These findings are reasonably consistent in direction, showing that minimizing night-time light exposure is associated with better cardiovascular and sleep outcomes, drawing on both large cohort data and smaller mechanistic sleep studies.
• Most of the evidence remains observational rather than from randomized trials that directly test darkening the sleep environment as an intervention, so the causal size of the effect is not fully established.