Differences in heart rate variability between depressed and non-depressed elderly
van der Kooy KG, van Hout HP, van Marwijk HW, de Haan M, et al.;
Commented by , 22 Mar 2006
Background
Untreated depression doubles the risk of cardiac mortality in older people. This study investigates whether heart rate variability (HRV) – a measure of cardiac autonomic functioning – may be implicated in this increased mortality.
Objective
To determine whether older subjects with Major Depressive Disorder (MDD) in primary care have lower HRV than non-depressed subjects.
Methods
Subjects – 6,719 over 55s were recruited for screening for depression from the waiting rooms of 14 family practices in The Netherlands. Those scoring > 4 on the 15-item Geriatric Depression Scale were consented to undergo a more detailed diagnostic interview process to establish MDD. Exclusion criteria were antidepressant treatment in the last 6 months, alcohol dependence, psychosis or cognitive impairment.
Heart Monitoring – HRV was assessed from a resting ECG. Blood pressure and body mass index were also recorded.
Statistics – Univariate regression analysis was used to determine whether HRV differed between the MDD group and controls. Multivariate analysis was then used in adjusting for age, sex, smoking, diabetes and cardiac medication.
Results
Screening revealed 187 eligible MDD subjects of whom 63 % participated. 124 subjects completed depression diagnosis and cardiovascular examination; compared to controls they had more cardiovascular disease, diabetes and used more prescription medication.
Univariate analysis of heart rate variability showed MDD subjects had less HRV than controls, even after adjusting for age, sex, smoking, diabetes and heart medication. In multivariate analysis, severity of depression did not add to the difference in HRV between MDD and controls: anxiety, demographic or medical variables did not display interaction between depression and HRV measures.
Dr Seymour's comments
Reduced HRV implies a disturbed balance between sympathetic and vagal branches of the autonomic nervous system. It is well established in the literature that in population studies, reduced HRV is predictive of cardiac events and cardiac mortality among health adults.
Previous studies on depression and HRV, performed on psychiatric inpatients, have produced conflicting results. This is the first study to investigate HRV in a depressed primary care population, finding an unequivocal link between MDD and reduced HRV.
The authors acknowledge that the cross-sectional design cannot prove a causal relationship between depression, reduced HRV, and cardiac death, though does lend weight to this hypothesis. They call for longitudinal studies investigating the relationship between depression and HRV.
At present, there is insufficient data to support measuring HRV routinely in depressed older adults. However, it is incumbent on both primary and secondary care physicians, and psychiatrists, to treat both major depression and cardiac risk factors concurrently.