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Concurrent sympathetic activation and vagal withdrawal in hyperthyroidism: Evidence from detrended fluctuation analysis of heart rate variability |
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| Authors: | Jin-Long Chen Yuo-Hsien Shiau Hung-Wen Chiu Niels Wessel Jürgen Kurths Woei-Chyn Chu |
| Institution: | a Department of Medical Informatics, Tzu Chi University, Hualien, Taiwan b Institute of Physics and Astronomy, University of Potsdam, Potsdam, Germany c Graduate Institute of Applied Physics, National Chengchi University, Taipei, Taiwan d Institute of Biomedical Engineering, National Yang-Ming University, Taipei, Taiwan e Graduate Institute of Medical Informatics, Taipei Medical University, Taipei, Taiwan f Department of Computer Science, National Chiao Tung University, Hsinchu, Taiwan g Institute of Physics, Humboldt University, Berlin, Germany h Potsdam Institute for Climate Impact Research, Potsdam, Germany |
| Abstract: | Despite many previous studies on the association between hyperthyroidism and the hyperadrenergic state, controversies still exist. Detrended fluctuation analysis (DFA) is a well recognized method in the nonlinear analysis of heart rate variability (HRV), and it has physiological significance related to the autonomic nervous system. In particular, an increased short-term scaling exponent α1 calculated from DFA is associated with both increased sympathetic activity and decreased vagal activity. No study has investigated the DFA of HRV in hyperthyroidism. This study was designed to assess the sympathovagal balance in hyperthyroidism. We performed the DFA along with the linear analysis of HRV in 36 hyperthyroid Graves’ disease patients (32 females and 4 males; age 30 ± 1 years, means ± SE) and 36 normal controls matched by sex, age and body mass index. Compared with the normal controls, the hyperthyroid patients revealed a significant increase (P<0.001) in α1 (hyperthyroid 1.28±0.04 versus control 0.91±0.02), long-term scaling exponent  , overall scaling exponent  , low frequency power in normalized units (LF%) and the ratio of low frequency power to high frequency power (LF/HF); and a significant decrease (P<0.001) in the standard deviation of the R-R intervals (SDNN) and high frequency power (HF). In conclusion, hyperthyroidism is characterized by concurrent sympathetic activation and vagal withdrawal. This sympathovagal imbalance state in hyperthyroidism helps to explain the higher prevalence of atrial fibrillation and exercise intolerance among hyperthyroid patients. |
| Keywords: | Hyperthyroidism Autonomic nervous system Heart rate variability Detrended fluctuation analysis Nonlinear dynamics |
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