What role does HDL play in sleep?

The role of HDL (high-density lipoprotein) in sleep is not fully established. HDL is best known for reverse cholesterol transport, anti-inflammatory, and antioxidant functions. Observational studies suggest that low HDL levels are associated with poor sleep quality, shorter sleep duration, and higher risk of sleep disorders such as obstructive sleep apnea. Potential mechanisms include HDL's involvement in steroid hormone synthesis (e.g., melatonin precursors) and modulation of systemic inflammation, which can affect circadian rhythms. Conversely, chronic sleep deprivation may lower HDL, indicating a bidirectional relationship. However, evidence is largely observational and insufficient for causal inference; randomized controlled trials are lacking. It is premature to consider HDL an independent sleep biomarker. Lifestyle interventions that raise HDL (aerobic exercise, Mediterranean diet, moderate alcohol intake) may indirectly improve sleep, but effects are modest and variable. For abnormal HDL or sleep issues, medical evaluation is essential, as other factors (stress, hormones, underlying conditions) are often more relevant.