Sleep problems commonly coexist with chronic pain conditions, with growing evidence that they may precede and contribute to pain persistence. Meanwhile, pain itself can disturb sleep, creating a bidirectional relationship. In this narrative review we explore how the sleep-pain relationship changes across the lifespan. In childhood and adolescence, poor sleep may predict the emergence of pain, possibly through neurodevelopmental impacts on pain modulation and affective regulation. In adulthood, sleep interacts with lifestyle, psychological state and occupational stressors to shape pain risk. In older adults, chronic pain and comorbidities such as sleep apnoea and depression may further impair sleep quality, reinforcing a vicious cycle. Across all stages, shared mechanisms, such as hypothalamic-pituitary-adrenal axis dysregulation, neuroinflammation, and impaired glymphatic clearance may contribute to this interplay. Recognising early sleep disturbance as a modifiable risk factor for later pain offers opportunities for prevention, while improving sleep may reduce the impact of established chronic pain.