Subjective and Objective Consequences of Stress in Subjects with Subjectively Different Sleep Quality—A Cross-Sectional Study

Background: Restful sleep plays an important role in long-term health and occupational safety. Heart rate variability (HRV) is used as stress indicator. The aim of this study was to determine whether HRV at rest or during sleep, as an objective indicator of stress, reflects subjectively assessed sleep quality. Methods: 84 subjects (37.3 ± 15.6 years) were classified into good sleepers and poor sleepers based on the results of the Pittsburgh Sleep Quality Index (PSQI). The cut-off value to distinguish between good and bad sleepers recommended by Buysse et al. 1989 is >5. Mental health status was determined using the 12-Item General Health Questionnaire (GHQ-12). A 24 h electrocardiogram (ECG) was recorded for HRV analysis (total and 6 h night phase). Results: The poor sleepers showed a significantly lower mental health status (p = 0.004). The multifactorial variance analysis of the total phase time parameters Min HR (p = 0.032, η(2) = 0.056) and SI (p = 0.015, η(2) = 0.072) showed significant interaction effects. In the 6h night phase, significant interaction effects were found for SDNN (p = 0.036, η(2) = 0.065) and SD2 (p = 0.033, η(2) = 0.067). In addition, there was a significant negative correlation between HRV and stress and a positive correlation between HRV and mental health. Conclusions: Although this study did not demonstrate a direct relationship between sleep quality and HRV, it was shown that there are important connections between sleep quality and mental health, and between HRV and mental health.