Heart rate variability and insomnia in depressed patients with breast cancer.

Objectives: Depression is associated with unhealthy autonomic regulation. However, whether patients with breast cancer (BC) with different degrees of depression can be identified from linear and non-linear dynamics in the autonomic nervous system is unclear. We aimed to evaluate the differences in linear and non-linear heart rate variability (HRV) parameters in patients with BC with different degrees of depression and the relationship between HRV parameters and depression and sleep disorders.

Methods: A total of 115 patients with BC were enrolled. According to their Self-Rating Depression Scale (SDS) scores, the patients were divided into a non-depressed group, a mildly depressed group and a moderately to severely depressed group. The Pittsburgh Sleep Quality Index (PSQI), HRV, linear index (including time and frequency domains) and non-linear index (including Poincare plot, approximate entropy (ApEn) and short-term fluctuation slope (DFAα1)) were evaluated.

Results: Compared with patients without depssion, patients with mild depression and moderate-to-severe depression had significant differences in the time domain, frequency domain index, the SD perpendicular to the line-of-identity (SD1) and DFAα1 of non-linear HRV and sleep quality. SDS and PSQI scores were correlated with HRV parameters.

Conclusions: The severity of depression in patients with BC is associated with reduced variability, complexity of cardiac dynamics and sleep disturbance.