High-frequency heart rate variability during worry predicts stress-related increases in sleep disturbances.

OBJECTIVE: The aim of this study was to evaluate whether high-frequency heart rate variability (HF-HRV) during waking restfulness and during worry predicts increases in sleep disturbances in response to a stressful life event. METHODS: A longitudinal study following up 22 individuals from well-defined periods of lower and higher stress was conducted. HF-HRV during waking restfulness and in response to a worry induction was measured during a low-stress period. Sleep disturbances were assessed using the Pittsburgh Sleep Quality Index (PSQI) and the Insomnia Severity Index (ISI) during low-stress and high-stress periods. RESULTS: During both the low- and high-stress periods, lower HF-HRV during worry was associated with greater PSQI scores. Importantly, lower HF-HRV during the worry induction prospectively predicted greater increases in the PSQI score from the low-stress to the high-stress periods. CONCLUSION: HF-HRV during worry might represent an index of vulnerability to stress-induced sleep disturbances.