RESEARKA

The curated corpus is dominated by observational cohort designs, with no long-term mortality randomized controlled trial (RCT) directly testing a circadian light-timing intervention included among the 25 accepted references. Without at least one adequately powered RCT that randomizes participants to a defined light-exposure prescription and follows them to a hard mortality endpoint, the causal arrow from light timing to survival cannot be established within this corpus. Similarly, cardiometabolic outcomes are informed only by indirect observational evidence (Hu 2025; Reytor-Gonzalez 2025) and a chrononutrition review (Nadeem 2024) rather than by a light-specific intervention trial. The absence of a diurnal-light RCT in non-diabetic community-dwelling adults leaves the headline cardiometabolic conclusion grounded entirely in surrogate or associational data, a limitation that aligns with the general caution that surrogate associations do not guarantee hard-outcome validity (Ioannidis 2005). Practitioners should therefore interpret the survival and metabolic findings as hypothesis-generating rather than practice-changing.

Citation Support

• source_1 Hu 2025
• source_2 Cheng 2024
• source_3 Panagiotou 2024
• source_4 Shim 2024
• source_5 Windred 2024