Evidence check: VDR in the context of sleep

Evidence for a direct link between VDR gene variants and sleep is weak. VDR (vitamin D receptor) mediates vitamin D activity, and vitamin D deficiency is associated with sleep disturbances – but these are mostly epidemiological observations, not causal genetic proof. The provided contexts contain no specific studies on VDR and sleep; they caution against overinterpreting DNA tests for chronotype or sleep (e.g., CLOCK gene). Therefore, the utility of a VDR test for sleep optimization is minimal. Mechanistically plausible, but clinically unsubstantiated. A sleep diary and vitamin D blood test are more reliable than a genetic test. Evidence: mechanistic/unclear.