Purpose of the Review <p>Obstructive sleep apnoea (OSA) is characterized by multidimensional variability that complicates diagnosis and treatment. Awareness on these aspects of variability is relevant for optimal treatment concepts.</p> Recent Findings <p>This review focuses on night-to-night variability in apnoea–hypopnoea index (AHI) – highlighting the risk of misclassification of the severity of OSA and the low negative predictive value of a single night sleep study – and its implications for accurately assessing disease severity and treatment response. We also consider other temporal fluctuations, including day-to-day symptom variability, low test-retest reproducibility of patient-reported outcomes such as the Epworth Sleepiness Scale, and night-to-night differences in treatment adherence and residual AHI on positive airway pressure therapy. Long-term changes related to age, weight, menopausal status, and evolving comorbidities further influence OSA expression. Access-related variability, e.g., disparities in availability of sleep clinics, polysomnography, and continuous positive airway pressure (CPAP) or non-CPAP treatments, adds another layer of complexity.</p> Summary <p>Integrating these temporal, treatment-related, and access dimensions is essential for accurate phenotyping, individualized management, and longitudinal monitoring, highlighting the need for precision approaches in the care of patients with OSA.</p>