What to watch with CLOCK and Müdigkeit?

CLOCK gene variants (e.g., rs1801260) influence circadian rhythm and may be linked to fatigue, sleep disturbances, or altered daytime sleepiness. However, effect sizes are generally small and heavily modulated by lifestyle factors (light exposure, sleep hygiene, stress). Some studies report associations with chronic fatigue, but evidence is mostly mechanistic or from GWAS with modest effect sizes. Direct causal evidence for fatigue is lacking. Consumer DNA tests do not provide clinically actionable results for CLOCK variants. A more reliable approach includes sleep diaries, actigraphy, and biomarkers (cortisol, melatonin). Caution: do not change sleep medications or supplements based solely on genetic results; persistent fatigue warrants medical evaluation.