The Sleep Gamble: Energetic Trade-offs and the Consequences of Sleep Deprivation

Sleep is a fundamental biological process that supports a wide range of physiological functions yet has received limited attention within the framework of life history theory. Life history theory explores how organisms strategically allocate energy across key life functions, such as growth, maintenance, reproduction, and defence, throughout the life cycle. While caloric intake is often used as the primary measure of energetic investment, this paper argues that sleep should be considered an equally important form of energy allocation. By examining the biological consequences of chronic sleep deprivation, this paper evaluates whether sleep can be considered a life history trait. The review draws on interdisciplinary evidence from human and animal studies to highlight the consequences of sleep loss across three domains: physical maintenance (e.g., bone density and structural integrity), reproductive function (e.g., hormonal imbalances and fertility reduction), and immune performance (e.g., inflammation, tumour progression, andneurological decline). These findings indicate that sleep loss forces the body to divert energy away from long-term health functions, leading to trade-offs consistent with life history predictions. Moreover, sleep supports energy conservation while enabling critical physiological processes, suggesting that it functions as a cost-effective biological strategy. Framing sleep as a dynamic form of energy investment opens new avenues for integrating sleep into life history theory. It offers a more comprehensive view of how humans adaptively manage energy resources across time.