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| ORIGINAL ARTICLE |
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| Year : 2022 | Volume
: 15
| Issue : 1 | Page : 34-37 |
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Obesity and heart rate variability: A cross-sectional study in obese young adults
BA Soumya1, Renu Lohitashwa2, Vidya M Nadiger1
1 Department of Physiology, SSIMS and RC, Davangere, Karnataka, India
2 Department of Physiology, JJMMC, Davangere, Karnataka, India
| Date of Submission | 21-Sep-2021 |
| Date of Decision | 25-Oct-2021 |
| Date of Acceptance | 01-Dec-2021 |
| Date of Web Publication | 24-Jan-2022 |
Correspondence Address:
Dr. B A Soumya
Department of Physiology, SSIMS and RC, Davangere, Karnataka
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/kleuhsj.kleuhsj_228_21
CONTEXT: Obesity is one of the important causative factors for multiple co-morbid conditions that can lead to metabolic and cardiac disorders. Many research studies indicate the association of obesity and sudden cardiac deaths.
AIMS: This study was aimed to evaluate the cardiac autonomic nervous system activity, given by the changes in heart rate variability (HRV) in healthy obese young adults.
SETTINGS AND DESIGN: This cross-sectional study included thirty obese young adult males of 18–25 years and 30 age-matched healthy adult males. Power spectral analysis of HRV was used to determine the autonomic imbalance.
SUBJECTS AND METHODS: HRV was performed using HRV software (Lab Chart 7). Numerical data of absolute values of low frequency (LF) and high frequency (HF) (in ms2), normalized units of LF and HF (in nu) and LF/HF ratio were expressed as mean ± standard deviation and analyzed.
RESULTS: On statistical analysis, it was found that HF in normalized units was significantly low in obese young adults compared to age-matched controls. LF (nu) and LF/HF ratio were higher in obese subjects compared to controls, though they were not statistically significant. Although there was negative correlation between HRV parameters and body mass index in obese individuals, it was not significant.
CONCLUSIONS: These results suggest that obese young adults present with changes in the autonomic nervous system, characterized by decrease in parasympathetic activity. Keywords: Frequency domain analysis, heart rate variability, obesity, sympathovagal balance
How to cite this article:
Soumya B A, Lohitashwa R, Nadiger VM. Obesity and heart rate variability: A cross-sectional study in obese young adults. Indian J Health Sci Biomed Res 2022;15:34-7 |
How to cite this URL:
Soumya B A, Lohitashwa R, Nadiger VM. Obesity and heart rate variability: A cross-sectional study in obese young adults. Indian J Health Sci Biomed Res [serial online] 2022 [cited 2022 May 22];15:34-7. Available from: https://www.ijournalhs.org/text.asp?2022/15/1/34/336304 |
| Introduction | |  |
Obesity creates an enormous socioeconomic and public health burden.[1] Obese individuals have higher prevalence of coronary heart disease, hypertension, hyperlipidemia, and diabetes mellitus, which are preventable by lifestyle changes.[2] Autonomic disturbances in obesity increase the incidence of sudden cardiac death.[3],[4]
Heart rate variability (HRV), an easy noninvasive technique depicting the power spectral analysis of heart rate, has proven to be a useful means to gain insight into sympathetic and parasympathetic control of heart activity.[5],[6]
Hence, the present study was under taken with the aim of evaluating the resting cardiac autonomic nervous system activity in healthy obese young adults.
| Subjects and Methods | | |
The study included thirty obese (body mass index [BMI] >30) young adult males of 18–25 years and 30 age-matched healthy adult males (BMI: 20–23) (Institutional Ethical committee clearance taken). Before recording of HRV, a detailed history and physical examination was done to exclude the syndromic obesity, endocrinological disorders, and other diseases such as diabetes mellitus, hypertension, or drugs interfering with the autonomic nervous system. Subjects were informed to avoid coffee, nicotine, or alcohol at least 24 h before the testing and to avoid food 2 h before testing. The examination was carried out between 10 AM and 1 PM at 24–25°C temperature. Ethical Clearance was obtained from Institutional Ethics Review Board, SSIMS & RC with Ref No IERB/98-2018 dated 23/01/2018.
The subjects were briefed about the procedure and written informed consent taken. They were then instructed to breathe quietly during the entire recording period with closed eyes and to avoid talking, moving hands, legs or body, coughing, and sneezing. All standard limb leads and chest leads were applied. The assessment of HRV was done by recording the 5 min E.C.G in supine position by HRV software (Lab Chart 7) after 15 min supine rest.
Heart rate variability
In the frequency domain analysis, the power spectrum for HRV was calculated with the fast Fourier transformation -based method. The power spectrum was subsequently divided into bands: power in low frequency (LF) range (0.04–0.15 Hz) and power in high frequency (HF) range (0.15–0.40 Hz).
Statistical analysis
Numerical data of absolute values of LF and HF (in ms2), normalized units of LF and HF (in nu) and LF/HF ratio were expressed as mean ± standard deviation (S. D). The comparison of HRV indices between the two study groups (obese and healthy young controls) was evaluated using unpaired Student's t-test. Correlation between BMI and HRV parameters was deduced using correlation analysis. A P < 0.05 was considered statistically significant.
| Results | | |
The subjects were analyzed in the study for LF and HF (in ms2); LF and HF (in nu); LF/HF ratio and heart rate. The results were expressed as mean ± S. D.
Low frequency power
Although mean LF (ms2) was higher in obese (444.17 ± 257.63) compared to controls (425.93 ± 135.87), it was not statistically significant [Table 1]. Similar results were obtained with normalized units of LF. | Table 1: Comparison of anthropometric and heart rate variability parameters between obese and controls
Click here to view |
High frequency power
Although mean HF (ms2) was lower in obese (416.73 ± 285.47) compared to controls (506.8 ± 281.91), it was not statistically significant. Significantly less values of HF in nu were obtained in obese (37.9 ± 7.37) compared to controls (43.87 ± 10.37) with P = 0.013 [Table 1].
Low frequency/high frequency ratio
LF/HF Ratio was higher in obese (1.18 ± 0.38) compared to controls (1.02 ± 0.43), but this difference was not statistically significant [Table 1].
Heart rate
There was no significant difference seen in the heart rate of obese (73.93 ± 6.87) and controls (76.8 ± 4.2) [Table 1].
Correlation between heart rate variability parameters and body mass index in obese subjects
Although there was negative correlation between HRV parameters and BMI in obese individuals, it was not statistically significant [Table 2]. | Table 2: Relationship between obesity indicator (body mass index) and heart rate variability parameters in obese subjects
Click here to view |
| Discussion | | |
This study investigating the power spectrum in HRV included obese subjects in the age group of 18–25 years. Spectral analysis of HRV is a noninvasive quantitative evaluation; efficient enough to detect the graded changes in the sympathovagal activity.[7] The measures of HRV reflect specific physiological autonomic regulatory activities. The modulation of vagus nerve discharge during respiration is reflected by the HF component. The LF component reflects the more gradual co-ordination between sympathetic and parasympathetic systems, influencing the variation in R-R interval.[8] Sympathovagal balance is denoted by the ratio of LF to HF power. Increased LF and LF/HF power indicates increased sympathetic tone.
In our study, obese young subjects showed increase in LF power (both in ms2 and nu), but not significant. Significantly lower HF power was seen in normalized units in obese individuals compared to controls (P = 0.013). Although not significant, the LF/HF Ratio was more in obese subjects. This could be attributed to the sympathetic overdrive and parasympathetic depression. Human obesity is attributed to marked sympathetic activation and baroreflex impairment.[9]
Similar results were obtained from Wu et al. who showed that the increased values of BMI were associated with shift in sympathovagal balance toward sympathetic dominance.[10] The LF/HF ratio has been proposed to be an accurate measure of the overall sympathovagal balance of the autonomic nervous system, in which higher values indicate a more sympathetically driven cardiovascular system.[11],[12]
Earlier studies on sympathetic nerve activity in obese persons have produced conflicting results. We have Piccirillo et al.,[13] who have shown that there is increased sympathetic modulation of arterial pressure, but diminished modulation of heart rate in obesty and also, according to Karason et al.,[14] obese patients have increased sympathetic activity and a withdrawal of vagal activity. In our study, though there was negative correlation between HRV indices and BMI in obese subjects, it was not statistically significant. This could be explained by the study conducted by Farah et al.[15] which demonstrated that the central obesity is a better indicator of HRV dysfunction. In their study, the largest waist circumference was related to the smallest parasympathetic modulation, and consequently, a greater cardiac autonomic dysfunction. Whereas, both central and general obesity were related to the sympathovagal imbalance of the heart in favor of sympathetic modulation was recorded by Guízar et al.[16] They proposed that the fat cells secrete various adipokines, including leptin, which is responsible for activating the neural pathways that increase the activity of the sympathetic nervous system.[17],[18]
Vanderlie et al.[19] observed that obese children had autonomic dysfunctions characterized by decreased parasympathetic activity and overall HRV.
The study by Barbara Zahorska et al.,[20] using a tilt table test, supported the hypothesis of autonomic imbalance in obesity. They also found that HRV values improve after treatment for weight reduction for 3 months.
Hence, to detect latent cardiac autonomic dysfunction in asymptomatic overweight individuals, short-term HRV test could be used as a screening tool at the clinics. There is increased mortality risk to obese individuals due to cardiovascular disorders related to either continuously lowered parasympathetic or altered sympathetic activation. Early detection and management by weight reduction, lifestyle changes, and regular physical exercise can reduce the risk as these are shown to increase HRV. HRV analysis can detect changes even before clinical signs appear. Hence, regular assessment of HRV measures in obese persons can be used as a biomarker for early detection and subsequent management of cardiovascular diseases.
| Conclusions | | |
The results of this suggest that obese young adults present with changes in the autonomic nervous system, characterized by decrease in parasympathetic activity and overall variability, which demonstrates the need for early attention to avoid future complications.
Suggestions
This study provides a glimpse of the differences in the power spectral indices of HRV between obese and normal weight individuals. Results from our study provide input to further studies on different obesity indicators and various time domain and frequency domain parameters of HRV to provide an understanding of the effectiveness of lifestyle modifications and early intervention to address obesity. Further research is necessary to deduce a definite relationship between the obesity indicators and duration of obesity on HRV indices.
Acknowledgment
We sincerely acknowledge all the study participants and technicians for their support in the conduction of this study.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]
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