The period frames sleep apnea as part of an integrated sleep-disordered breathing system, with insomnia co-occurring with apnea and daytime impairment shaping diagnostic priorities. It emphasizes nocturnal cardiovascular dynamics and the value of continuous recording and standardized sleep staging to reveal patterns of breathing disturbances within broader sleep architecture. Pediatric implications begin to emerge, signaling a shift toward inclusive research encompassing diverse populations. Historical Significance: Foundational studies established the methodological and clinical basis for subsequent research in sleep-disordered breathing. Early work linking sleep to arterial pressure regulation and nocturnal hemodynamics created connections between apnea and cardiovascular responses. Standardized terminology and scoring systems enabled consistent cross-laboratory comparisons, while pediatric observations extended the framework to infant sleep and the Sudden Infant Death Syndrome context.