Objective: Several reports suggested that people with mental disorders have increased risks of coronary heart disease and sudden cardiac death. These risks may be associated with altered neural regulation in the cardiovascular systems. The activities of the autonomic nervous system (ANS), which modulates a human’s internal environment, decrease with aging in the healthy adult. However, in people with mental disorders, the change in ANS activities with aging remains unknown. The present study was designed to examine whether heart rate variability, which is considered an indicator of ANS activity, is altered with aging in subjects with mental disorders.
Methods: One hundred thirty-three subjects with mental disorders and 94 healthy subjects participated in the current study. The ANS activities were measured during a resting condition by means of heart rate variability (HRV) power spectral analysis. In general, power spectral analysis of HRV has shown at least two distinct regains of periodicity in electrocardiogram R-R intervals. The high-frequency component (<0.15 Hz) is a major contributor to reflecting parasympathetic nervous system (PNS) activity, and the low-frequency component (<0.15 Hz) is dually mediated by the sympathetic nervous system (SNS) and PNS activities. In addition, the Global Assessment Scale (GAF) was used for mental disorder subjects to evaluate social adjustment prior. The mental disorders and healthy groups were classified into five groups according to their age: 20s, 30s, 40s, 50s, and over 60. The indexes of the spectral powers were logarithmically transformed for statistical analyses.
Results: Significant interactions of age and subject groups were found in HR, TP, LF, and HF in the two-way ANOVA. In the healthy group, HR was not significantly different, while TP (p < .01), LF (p < .01), and HF (p < .01) were significantly decreased with aging. On the contrary, in the mental disorders group, HR was significantly lower (p < .05) in the older subjects compared with the younger subjects, while ANS activities showed no significant difference in any age groups. The GAF scores were lower (that is, low social adjustment ability) in the young subjects compared with the old subjects (20s, 23.0 ± 2.8; 30s, 27.0 ± 7.0; 40s, 29.2 ± 7.9; 50s, 33.0 ± 7.4; and over 60, 33.0 ± 11.1, M ± SD).
Conclusions: Our findings indicate that younger mental disorder groups may have reduced sympathovagal activity and lower GAF scores. Although causes and consequences remain to be elucidated, our findings suggest the possibility that such autonomic depression could be a crucial risk factor in undermining the health and, ultimately, the quality of life of mentally disordered patients.