Insomnia and circadian misalignment: an underexplored interaction towards cardiometabolic risk

Insomnia remains the most prevalent sleep disorder worldwide, and its pathophysiology suggests an interface with circadian rhythm sleep-wake disorders (CRSWDs). Some epidemiological studies have linked insomnia and circadian misalignment with adverse cardiometabolic outcomes, but the mechanisms underlying this relationship are still unclear. The autonomic nervous system (ANS) has been pointed out as a crucial/key mediator that triggers cardiometabolic risk. Therefore, a critical review of the literature focused on the past ten years was conducted to highlight the relationship between insomnia, circadian misalignment and cardiometabolic risk, with particular emphasis on the influence of the ANS. Shift work, as a model of circadian misalignment, was shown to increase both cardiovascular and metabolic risk and so may integrate a proof of concept on this link. Furthermore, there is good evidence from previous studies supporting that cardiac autonomic dysfunction is indeed a possible mechanism that potentiates cardiometabolic risk in insomniacs and individuals with a misalignment of the circadian timing system (e.g., shift workers), via changes in autonomic variables. Further research is however required in order to definitively establish this interactive relationship.