Sleep, melatonin, and cardiovascular disease

Melatonin is a key circadian mediator that governs the synchronisation of peripheral biological rhythms with the central clock (ie, the suprachiasmatic nucleus) and regulates the sleep–wake cycle. The synthesis of this hormone by the pineal gland follows a nyctohemeral pattern that aligns with the day–light cycle: production is low during the day and high at night. The rhythmic secretion of melatonin from the pineal gland is controlled by a multisynaptic pathway, through the retinal–hypothalamic–suprachiasmatic nucleus tract to the superior cervical ganglia. These ganglia convey circadian information to the pineal gland, dictating nocturnal melatonin secretion through sympathetic adrenergic stimulation. Melatonin also has cardiovascular effects, including vasodilation and scavenging of reactive oxygen species. 1 Tobeiha M Jafari A Fadaei S et al. Evidence for the benefits of melatonin in cardiovascular disease. Front Cardiovasc Med. 2022; 9888319 Crossref Scopus (17) Google Scholar Sleep disturbance and cardiovascular disease are common comorbidities. 2 Belloir J Makarem N Shechter A Sleep and circadian disturbance in cardiovascular risk. Curr Cardiol Rep. 2022; 24: 2097-2107 Crossref PubMed Scopus (2) Google Scholar Disrupted sleep might increase the risk of cardiovascular disease through multiple mechanisms, including sympathetic activation. However, emerging data suggest that the relationship between poor sleep and cardiovascular disease could be bidirectional—ie, cardiovascular disease might elicit sleep disorders.