Is CYP1A2 useful for Müdigkeit?

CYP1A2 is the primary enzyme metabolizing caffeine. Genetic variants (e.g., rs762551) classify individuals as fast or slow caffeine metabolizers. Fast metabolizers (e.g., *1A/*1A) clear caffeine quickly, potentially reducing its anti-fatigue effect. Slow metabolizers (e.g., *1F/*1F) maintain higher caffeine levels longer, which may better alleviate fatigue but also increase risks of jitters, palpitations, or sleep disruption. Evidence comes from human observational and GWAS studies, but the impact on daily fatigue is modest and highly influenced by lifestyle, sleep, and other factors. A consumer DNA test can suggest a tendency, but it cannot replace a medical workup for underlying causes of fatigue (e.g., sleep disorders, anemia, thyroid issues). Moreover, many DTC tests lack clinical validation. Conclusion: CYP1A2 genotyping may offer a clue, but it is not a standalone solution for fatigue. Clinical utility remains limited.