Conclusion
Sleep restriction influences cardiac autonomic tone more than sleep fragmentation. There is a shift towards higher sympathetic activity and lower parasympathetic activity during restricted sleep, especially during light sleep stages. Here, HR increases and HRV decreases. This indicates that sleep restriction may cause more stress for the organism than a sleep fragmentated night. In general, our study showed that sleep interventions like fragmentation and restriction have an impact on parameters of the cardiac autonomic tone, especially during the light sleep stages. During REM and N3 sleep, the body is probably able to hold parameters stable: they do not change as much as they change anyway in a physiological manner. In a next step, the interventions may be modified, fragmentation may be increased. Also, recovery time should be investigated.