Is Dark Sleep Environment good for metabolic health?

The evidence points that way, though it's not yet conclusive. 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. That's reflected in an evidence score of 48/100 for its role in metabolic health, drawn from 6 studies, with an estimated impact on longevity rated moderate (42/100).