Evidence check: TCF7L2 in the context of Schlaf

TCF7L2 is a well-replicated risk factor for type 2 diabetes (OR ~1.3–1.5), but not directly for sleep. Some studies suggest a possible link via circadian rhythm or glucose metabolism, but evidence for sleep as an independent endpoint is weak and mechanistic. The provided context contains no direct associations between TCF7L2 and sleep. Therefore, an evidence-based statement on sleep quality or disorders based on this gene is currently not possible. The primary relevance of TCF7L2 remains diabetes risk, not sleep regulation. Caution against overinterpretation in consumer tests.