|Year : 2017 | Volume
| Issue : 1 | Page : 23-26
Evaluation of cardiac autonomic function in overweight males: A cross-sectional study
Debasish Das, Himel Mondal
Department of Physiology, Maharaja Krishna Chandra Gajapati Medical College, Ganjam, Odisha, India
|Date of Web Publication||6-Feb-2017|
Department of Physiology, Maharaja Krishna Chandra Gajapati Medical College, Ganjam - 760 004, Odisha
Source of Support: None, Conflict of Interest: None
Background and Aim: Cardiovascular autonomic function tests (CAFTs) are non-invasive tests that can assess both sympathetic and parasympathetic autonomic functions. Autonomic dysfunction may be considered as a risk factor for obesity and vice versa. For measurement of obesity, body mass index (BMI) is a simple, valid and inexpensive method. Hence, this study was designed to evaluate the effect of obesity based on BMI criteria on autonomic nervous system based on CAFT in young adult males. Methods: A cross-sectional study was carried out on 43 young adult males in the age group of 18–25 years with an age-matched control (n = 43) group. After initial screening, anthropometric measurements were recorded. CAFTs were performed and recorded by the Cardiac Autonomic Neuropathy Analysis System (CANWin). Unpaired t- test was done to compare the parameters of study and control groups in Microsoft Excel® 2010. Results: Parasympathetic test parameters of study and control groups when expressed in mean ± standard deviation were not found statistically significant (P > 0.05). The fall in systolic blood pressure (BP) in orthostatic test of study group (12.19 ± 4.8 mmHg) was significantly (P = 0.0001) higher than that of control group (7.33 ± 5.16 mmHg). Increase in diastolic BP in isometric handgrip exercise test of study group (11.84 ± 5.39 mmHg) was significantly less (P = 0.004) than that of control group (16.39 ± 8.71 mmHg). Conclusion: Overweight young males have altered sympathetic activity but parasympathetic activity did not show any significant difference when compared to normal weight males.
Keywords: Autonomic function test, autonomic neuropathy, overweight male, screening test, sympathetic dysfunction
|How to cite this article:|
Das D, Mondal H. Evaluation of cardiac autonomic function in overweight males: A cross-sectional study. Adv Hum Biol 2017;7:23-6
| Introduction|| |
Autonomic nervous system (ANS) controls a wide range of metabolic, cardiopulmonary and other visceral functions. Since ANS is involved in energy metabolism, it may be conceived that persons with idiopathic obesity have an alteration in their ANS and this alteration may promote obesity. In experimental animals, when ventromedial hypothalamic lesion was induced, it has shown a combination of decrease in sympathetic activity, increase in parasympathetic activity and obesity. In obese animals, decreased level of sympathetic nervous system activity may lead to excessive energy storage in adipose tissue. The reason behind it may be decreased lipolysis and increase in lipogenesis. Cardiovascular autonomic function tests (CAFTs) assess both sympathetic and parasympathetic nervous system activities. These non-invasive set of tests are easily administrable in small clinical settings. Body mass index (BMI) is a simple, valid and inexpensive surrogate measure of obesity suggested by the World Health Organization (WHO). Screening of obesity by BMI helps to stratify people with future health risks. With this background, our study was aimed at assessing the extent of ANS dysfunction tested by CAFT in young adult males whose BMI is more than 25.
| Methods|| |
After designing the study protocol, clearance from the Institutional Ethics Committee was obtained. A cross-sectional study was carried out from October 2015 to September 2016 in the Postgraduate Research Laboratory of the Department of Physiology, Maharaja Krishna Chandra Gajapati Medical College. Forty-three otherwise healthy male students with BMI >25 in the age group of 18–25 years were taken as study group. Forty-three age-matched non-obese (BMI: 18.5–25) male students were taken as control group. Students with a history of chronic illness, on any medication and smokers were excluded from the study. The aim of the test was explained to the participants and written consent was obtained from all participants.
Height was measured by a stadiometer to the nearest 0.1 cm with the participants standing in erect posture. Weight was recorded in kg with a digital weighing scale with a sensitivity of 0.1 kg. BMI was calculated using Quetelet's equation. Basal heart rate (HR) was measured after 15 min rest on a comfortable couch. The laboratory room temperature was set at 24°C and humidity at 50%.
CAFTs were performed and recorded by Windows ® PC-based Cardiac Autonomic Neuropathy Analysis System Version 1.0 (CANWin). It analyzes both sympathetic and parasympathetic ANS responses of the participants. It uses oscillometric method for non-invasive blood pressure (BP) measurement with an accuracy of ±3 mmHg. It uses Lead I and Lead II of electrocardiogram with an HR measurement accuracy of ±1 beats/min (bpm). Being automatic, CANWin eliminates the need of manual recording of readings and reduces calculation errors. Before actual test, a trial test was done with verbal instructions.
Tests for parasympathetic nervous system are as follows:
- HR response to deep breathing: Expiration-inspiration ratio (E:I)
- HR response to standing: 30:15 ratio
- HR response to Valsalva maneuver: Valsalva ratio.
Tests for sympathetic nervous system are as follows:
- Postural hypotension: Fall in systolic BP (SBP)
- Sustained handgrip (isometric exercise) test: Increase in diastolic BP (DBP)
A sample of summary report of cardiac parasympathetic test obtained by CANWin is shown in [Figure 1] and sympathetic test is shown in [Figure 2]. Data obtained were preserved for statistical analysis.
|Figure 1: Sample report of parasympathetic cardiovascular autonomic function test.|
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|Figure 2: Sample report of sympathetic cardiovascular autonomic function test.|
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Data were entered, calculated and analysed statistically in Microsoft Excel ® 2010 data analysis tools. Unpaired t-test was used to compare the parameters of study and control groups. Results were considered statistically significant if there is two-tailed P < 0.05.
| Results|| |
The mean age of study group was 19.56 ± 1.26 years and control group was 19.53 ± 2.37 years. There was no significant difference in age between the study group and control group (P = 0.94) as we desired. Mean BMI of the study group (28.01 ± 2.02) was significantly higher (P < 0.0001) than the control group (21.54 ± 1.99). According to the WHO categorisation, the study group was in 'pre-obese' category and control group was in 'normal range' category. Age and anthropometric parameters of study and control groups are shown in [Table 1].
|Table 1: Age and anthropometric parameters of control and study groups expressed in mean±standard deviation|
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Resting HR (bpm) of study group (79.21 ± 5.22) was significantly (P = 0.01) higher than that of control group (75.28 ± 8.34). Resting systolic (128.72 ± 9.96) and diastolic (74.17 ± 9.12) BP (in mmHg) of study group was significantly higher than the systolic (120.84 ± 8.69) and diastolic (68.48 ± 7.06) BP of control group. The comparison is shown in [Figure 3].
|Figure 3: Resting systolic and diastolic blood pressure of control and study groups.|
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Parasympathetic test variables of control group were compared with that of the study group by unpaired t-test, and the results found are shown in [Table 2].
|Table 2: Parasympathetic cardiovascular autonomic function test variables in control and study groups expressed in mean±standard deviation|
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Normal, borderline and abnormal values in CAFT for young adults are shown in [Table 3]., E:I ratios of study group (1.38 ± 0.18) and control group (1.35 ± 0.19) were both in normal category (>1.2) and the difference between the two groups was not statistically significant (P = 0.45). Valsalva ratio of study group (1.73 ± 0.36) and control group (1.68 ± 0.85) was also in normal category (≥1.21) and the t-test did not indicate any significant difference among the two groups (P = 0.72). The 30:15 ratio of study group (1.37 ± 0.18) and the control group (1.32 ± 0.18) was in normal category (≥1.04) and difference between the two groups was not statistically significant (P = 0.20).
|Table 3: Normal, borderline and abnormal values in cardiovascular autonomic function test for young adults|
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The fall in SBP in orthostatic test of study group (12.19 ± 4.8 mmHg) was in 'borderline' category and control group (7.33 ± 5.16 mmHg) was in 'normal' category and the difference of the two groups was statistically significant [P = 0.0001, [Table 4]. Increase in DBP in isometric handgrip exercise test of study group (11.84 ± 5.39 mmHg) was in borderline category and was significantly [P = 0.004, [Table 4] less than that of control group (16.39 ± 8.71 mmHg) which was in normal category.
|Table 4: Sympathetic cardiovascular autonomic function test variables in control and study groups expressed in mean±standard deviation|
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| Discussion|| |
The results of CAFTs of our study revealed that there was no significant difference in parasympathetic activity of overweight and normal weight participants. However, decreased sympathetic activity is found in overweight participants. Çolak et al. reported normal activity of parasympathetic system and hypoactivity of sympathetic nervous system in obese participants. Bedi et al. and Pal et al. also have reported similar results. Valensi et al. have also demonstrated sympathetic insufficiency in obese state. Decrease in sympathetic activity causes a disordered homeostatic mechanism which promotes excessive energy storage as suggested in a remarkable paper by Peterson et al. On the other hand, Shetty et al. and Yakinci et al. found reduced parasympathetic activity but no significant difference in sympathetic activity in overweight participants while comparing with normal weight participants. Nagai et al. and Garg et al. reported that obese children and adolescents both have lower sympathetic and parasympathetic activities. These diverse results in different studies may be due to different age group of sample and difficulty in controlling variables such as family history, diet, level of physical activity and stress level. Though we have carried out sympathetic ANS test with automated instrument, it may be done with simple instruments: BP-measuring instrument, hand grip dynamometer and a couch. Non-invasive nature and easy operation enable us to carry out these tests with less expertise and minimal expense. A study by Fleischer et al. concluded that cardiac autonomic neuropathy can be tested even at home with appropriate device. Sympathetic CAFT may be used as a screening test for young adults to find out any sympathetic dysfunction at an early stage. A prescription of exercise or increased physical activity helps in weight reduction and might be beneficial for maintaining ANS function within normal limit.
Our study has a limitation that we have taken only male participants of limited age difference.
| Conclusion|| |
Overweight young adult males have altered sympathetic activity but parasympathetic activity of overweight males does not show any significant difference in comparison with normal weight males. Hence, a screening by CAFT, especially sympathetic CAFT, may help in the detection of altered ANS activity in the early stage for appropriate steps towards prevention of any complication related to altered ANS function.
We thank the 1st year medical students of 2015–2016 batch of Maharaja Krishna Chandra Gajapati Medical College for their participation in the study.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4]