Depressive symptoms have been associated with increased cardiac morbidity and mortality rates, but the pathophysiologic mechanism linking depressive symptoms to cardiovascular outcome has yet to be fully understood. Lower heart rate variability has also been associated with increased risk of cardiac events in healthy individuals and in patients with coronary artery disease. Findings regarding a relationship between depressive symptoms and heart rate variability that could explain increased cardiovascular risk have been inconsistent across studies.
As an ancillary study to the Women's Health Initiative Observational Study, 3372 postmenopausal women aged 50 to 83 years were enrolled for further evaluation using 24-hour ambulatory electrocardiographic monitoring. A shortened version of the Center for Epidemiological Studies Depression Scale and the Diagnostic Interview Schedule were administered. Women with adequate electrocardiographic data and depressive symptom information and without coronary artery disease were analyzed (n = 2627).
Two hundred sixty-nine women (10.2%) had depressive symptoms as measured using the 2 instruments. Women with depressive symptoms had a higher mean ± SD heart rate (77.4 ± 9.6 vs 75.5 ± 8.5 beats/min) and lower heart rate variability than women without depressive symptoms. All differences remained significant after adjusting for age (P<.01).
Women with depressive symptoms had significant reductions in heart rate variability and higher heart rates, suggestive of increased sympathetic tone. These findings may contribute to the increased cardiac morbidity and mortality rates associated with depression in other studies.