How are CLOCK and fatigue related?

The provided knowledge contexts contain no specific information about the CLOCK gene or its relationship to fatigue. CLOCK (Circadian Locomotor Output Cycles Kaput) is a core circadian gene, and some studies suggest possible links between CLOCK variants and fatigue or sleep disturbances. However, evidence is mostly mechanistic or from GWAS with small effect sizes. Without direct context data, the explanatory power is limited. No clinical recommendations can be derived. Lifestyle factors such as sleep hygiene, stress management, and exercise have a much larger impact on fatigue than single gene variants. Genetic testing for CLOCK is not currently validated as a diagnostic or predictive tool for fatigue.