Cardiovascular and autonomic consequences of sleep fragmentation

Introduction: Sleep disruption is commonly found in normal individuals and those with sleep disorders. Risk factors for sleep fragmentation involve a combination of lifestyle, environmental, psychosocial factors and/or medical conditions. The main objective of this study was to analyse the impact of acute, induced sleep fragmentation upon autonomic cardiovascular regulation, measured by a non-invasive haemodynamic measurement technique. Material and methods: The authors analysed beat-to-beat measurements of haemodynamic and autonomic parameters at 5-time points during sleep fragmentation: 9:00 a.m. (baseline), 9:00 p.m., 00:30 a.m., 4:00 a.m., and 7:30 a.m. Differences in the mean values for chronotropic parameters, cardiac contractility, parameters related to blood pressure regulation and workload of the left ventricle, and autonomic parameters were examined in seventeen healthy male volunteers. Direct results obtained from every time point were analysed using analysis of variance with repeated measures or the Friedman rank sum test. Results: Sleep fragmentation had a significant negative impact on haemodynamic parameters related to cardiac contractility (SV p < 0.001, IC p < 0.001, HI p < 0.001); parameters related to workload of the left ventricle (CO p < 0.001, LVWI p < 0.001, ACI p < 0.001); parameters related to blood pressure regulation (sBP p = 0.001, TPR p < 0.001); on chronotropic parameters (HR p < 0.001, PEP p < 0.001, LVET p < 0.001) and an indicator of cardiac autonomic regulation: LF-RRI (p = 0.001). Conclusions: Acute sleep fragmentation can modify haemodynamic control and autonomic cardiovascular regulation in healthy men; the most important changes were seen in the morning hours (4:00 a.m.). Therefore, conditions of chronic sleep fragmentation (e.g. shift work, uniformed services, clinicians), might lead to disturbance in the autonomic nervous system and therefore to problems with homeostasis in the cardiovascular system. Future research is needed in standardized conditions with large-scale studies to clarify the effects of chronic sleep fragmentation.