Objective: To determine if depression associated with low heart rate variability (HRV) in patients post myocardial infarction (MI), but not in patients with stable coronary heart disease (CHD), may be the result of differential associations of somatic and cognitive depressive symptoms with HRV.
Methods: To examine the association of somatic and cognitive depressive symptoms with 24-hour HRV, we performed a cross-sectional study of 863 outpatients with stable CHD. The severity of somatic and cognitive depressive symptoms was determined using factor analysis of items of the Patient Health Questionnaire (PHQ-9). Time-domain (SDNN, SDANN) and frequency-domain (VLF, LF, HF, WBF) indices of HRV were derived using ambulatory monitoring.
Results: Unadjusted analyses revealed that somatic symptom scores were significantly associated with HRV (r = -.09 for SDNN; r = -.08 for SDANN; r = -.08 for LnVLF; r = -.08 for LnLF; r = -.10 for LnHF; r = -.08 for LnWBF). After adjustment for demographic variables, comorbidities, and lifestyle factors, somatic symptom scores were no longer associated with lower HRV, with the possible exception of LnWBF (r = -.06). Cognitive depressive symptom scores were not associated with HRV using either unadjusted or adjusted analyses.
Conclusions: We found that somatic depressive symptoms were associated with lower HRV, although cognitive depressive symptoms were not. The inverse association of somatic symptoms with HRV was largely explained by differences in comorbidities and lifestyle factors. These results suggest that individual symptoms of depression may have differential associations with HRV.