1Dept. of Obstetrics & Gynecology, College of Korean Medicine, Dong-Guk University
2Gireum Korean Medical Clinic, Dong-Guk University
3College of Korean Medicine, Dong-Guk University
Correspondence to: Dong-Il Kim, Dept. of Korean Medicine Obstetrics & Gynecology, Ilsan Dong-Guk University Korean Medicine Hospital, 27 Dongguk ro, Ilsandong-gu, Goyang-si, Gyeonggi-do, Korea, Tel:+82-31-961-9060, Fax:+82-31-961-9009, E-mail: obgykdi@hanmail.net
Received March 16, 2021 Revised April 8, 2021 Accepted May 14, 2021
The object of this study was to examine whether there was a significant difference between morning and afternoon in heart rate variability(HRV) in healthy Korean adults. In addition, the correlation between the characteristics of the subjects and the test results was analyzed.
Methods
From January 8, 2021 to January 29, 2021, twenty healthy subjects received short-term HRV test once in the morning(6:00~12:00) and twice in the afternoon(12:00~18:00). We used IBM SPSS Statistics 27 to test for statistical significance.
Results
The mean heart rate and PSI decreased significantly and SDNN increased significantly in the morning compared to the afternoon. There was no significant difference except RMSSD in HRV conducted at 2 hours intervals in the afternoon. Age had a significant difference in SDNN and TP, and exercise in average heart rate. Age, weekly exercise frequency, and monthly drinking frequency showed significant correlations with HRV indicators. As a result of multiple regression analysis, monthly drinking frequency was a variable that had a significant influence on TP.
Conclusions
The results of the tests performed with short interval were relatively consistent, and when comparing the results of the afternoon and the next morning, there were significant differences in several indicators. In the future, the number of HRV measurements should be increased and a larger-scale follow-up study including more subjects will be needed.
HRV*:Heart Rate Variability; GARS†:Global Assessment of Recent Stress; HR‡:Heart Rate; SDNN§:Standard Deviation of Normal to Normal; RMSSD||:Root Mean Square of Successive Differences between adjacent R-R intervals; PSI¶:Physical Stress Index; TP**:Total Power; LF++:power in Low Frequency range; HF‡‡:power in High Frequency range
Table 3
Comparing HRV Parameters with Short Measurement Interval
(n=20)
Categories
Characteristics
Mean±SD
p-value
1st HRV
2nd HRV
HRV* Parameters
Mean HR† (bpm)
72.70±8.59
74.20±9.50
0.198
SDNN‡
37.82±22.48
33.67±14.84
0.263
RMSSD§
35.43±30.31
25.52±13.12
0.037#
PSI||
65.80±50.30
74.26±53.34
0.478
TP¶
1303.93±1440.09
1074.77±781.06
0.852
LF**
479.34±758.86
361.30±445.45
0.370
HF++
455.36±764.50
291.51±441.80
0.100
LF/HF
1.61±1.41
2.83±3.72
0.093
HRV*:Heart Rate Variability; HR†:Heart Rate; SDNN‡:Standard Deviation of Normal to Normal; RMSSD§: Root Mean Square of Successive Differences between adjacent R-R intervals; PSI||:Physical Stress Index; TP¶:Total Power; LF**:power in Low Frequency range; HF++:power in High Frequency range; (#, p<0.05)
Table 4
Comparing HRV Parameters with Long Measurement Interval
(n=20)
Categories
Characteristics
Mean±SD
p-value
Mean value of 1st & 2nd HRV
3rd HRV
HRV* Parameters
Mean HR† (bpm)
73.45±8.32
69.30±8.99
0.023#
SDNN‡
35.75±16.99
45.01±20.67
0.001##
RMSSD§
30.47±20.56
35.94±25.86
0.140
PSI||
70.03±46.14
46.05±35.71
0.006##
TP¶
1189.35±1031.64
1550.90±1451.93
0.204
LF**
420.32±568.54
463.56±435.47
0.601
HF++
373.44±584.21
571.58±921.23
0.247
LF/HF
2.22±2.41
1.87±2.12
0.433
HRV*:Heart Rate Variability; HR†:Heart Rate; SDNN‡:Standard Deviation of Normal to Normal; RMSSD§: Root Mean Square of Successive Differences between adjacent R-R intervals; PSI||:Physical Stress Index; TP¶:Total Power; LF**:power in Low Frequency range; HF++:power in High Frequency range; (#, p<0.05, ##, p<0.01)
Table 5
Comparing Total HRV Parameters According to Subject Characteristics
Categories
Characteristics
Mean±SD of Total HRV*
Mean HR‡ (bpm)
p-value
SDNN§
p-value
RMSSD||
p-value
PSI¶
p-value
TP**
p-value
LF++
p-value
HF‡‡
p-value
LF/HF
p-value
Age
Under 30s (n=11)
72.00± 7.47
0.968
45.42± 20.54
0.046#
38.88± 26.44
0.131
57.66± 45.61
0.602
1749.45± 1253.62
0.029#
594.25± 559.03
0.084
643.62± 872.40
0.118
2.07± 2.30
0.930
Over 40s (n=9)
72.15± 8.73
30.79± 7.06
24.25± 9.05
67.38± 33.49
772.58± 289.96
239.76± 163.52
189.99± 123.40
2.15± 1.52
Gender
Female (n=15)
71.87± 8.67
0.850
40.70± 19.11
0.418
34.07± 23.03
0.535
59.70± 42.08
0.662
1413.50± 1153.81
0.461
473.97± 516.87
0.520
495.87± 774.07
0.535
2.28± 2.21
0.271
Male (n=5)
72.67± 5.34
33.24± 9.44
26.97± 10.40
69.05± 35.82
998.96± 676.31
317.02± 179.26
270.34± 207.42
1.56± 0.59
GARS
≤25 (n=10)
70.30± 9.72
0.327
39.94± 17.90
0.783
32.54± 14.71
0.961
60.01± 44.53
0.827
1267.44± 942.11
0.863
466.33± 587.40
0.766
371.72± 405.57
0.667
2.20± 2.32
0.824
>25 (n=10)
73.83± 5.32
37.73± 17.54
32.05± 27.40
64.06± 37.00
1352.29± 1205.90
403.13± 304.74
507.24± 893.13
2.00± 1.59
Job
Yes (n=16)
72.85± 6.94
0.383
39.00± 17.51
0.935
32.18± 22.75
0.962
62.16± 37.96
0.979
1323.19± 1104.50
0.914
430.96± 498.30
0.943
439.55± 710.86
0.999
1.85± 1.77
0.262
No (n=4)
68.92± 11.50
38.18± 18.93
32.77± 17.72
61.55± 53.62
1256.55± 965.91
449.81± 280.11
439.23± 624.88
3.10± 2.55
Drinking
Yes (n=16)
71.29± 8.04
0.391
40.40± 19.03
0.434
34.23± 23.51
0.435
60.56± 44.09
0.750
1415.51± 1153.34
0.384
488.59± 496.27
0.304
498.72± 750.61
0.450
2.28± 2.12
0.421
No (n=4)
75.17± 7.10
32.60± 3.99
24.58± 6.26
67.94± 17.47
887.29± 297.98
219.29± 107.71
202.54± 80.39
1.38± 0.67
Caffeine intake
Yes (n=15)
72.60± 6.55
0.612
38.25± 16.27
0.800
31.22± 22.57
0.709
61.03± 33.14
0.893
1306.93± 1062.83
0.983
466.33± 511.84
0.605
421.14± 728.60
0.841
2.16± 2.01
0.830
No (n=5)
70.47± 11.73
40.60± 22.09
35.51± 19.38
65.07± 60.84
1318.67± 1150.74
339.94± 241.62
494.52± 569.88
1.93± 1.93
Exercies
Yes (n=10)
68.63± 5.29
0.047#
43.27± 20.89
0.263
39.03± 26.35
0.165
52.26± 37.85
0.285
1601.83± 1323.15
0.231
531.94± 613.16
0.355
585.58± 877.70
0.349
1.99± 2.13
0.795
No (n=10)
75.50± 8.70
34.40± 12.27
25.56± 13.12
71.81± 41.42
1017.90± 636.88
337.53± 207.73
293.39± 393.17
2.22± 1.84
HRV*:Heart Rate Variability; GARS†:Global Assessment of Recent Stress; HR‡:Heart Rate; SDNN§:Standard Deviation of Normal to Normal; RMSSD||:Root Mean Square of Successive Differences between adjacent R-R intervals; PSI¶:Physical Stress Index; TP**:Total Power; LF++:power in Low Frequency range; HF‡‡:power in High Frequency range; (#, p<0.05)
Table 6
Comparing Morning HRV Parameters According to Sleep Quality
(n=20)
Categories
Characteristics
Mean±SD
p-value
Sleep well (n=14)
Sleep poorly (n=6)
3rd HRV*
Mean HR† (bpm)
73.86±7.81
70.00±10.45
0.372
SDNN‡
38.19±25.28
36.98±16.05
0.916
RMSSD§
35.51±35.19
35.25±16.52
0.987
PSI||
72.57±55.43
49.99±34.57
0.372
TP¶
1414.43±1658.23
1046.08±785.77
0.614
LF**
564.19±901.02
281.34±101.42
0.460
HF++
467.41±856.37
427.27±559.32
0.918
LF/HF
1.70±1.58
1.39±1.02
0.667
HRV*:Heart Rate Variability; HR†:Heart Rate; SDNN‡:Standard Deviation of Normal to Normal; RMSSD§: Root Mean Square of Successive Differences between adjacent R-R intervals; PSI||:Physical Stress Index; TP¶:Total Power; LF**:power in Low Frequency range; HF++:power in High Frequency range
Table 7
Correlations between Subject Characteristics and HRV Parameters
(n=20)
1
2
3
4
5
6
7
8
9
10
11
12
13
1. MHR*
1
2. SDNN†
−.533 (0.015#)
1
3. RMSSD‡
−.556 (0.011#)
.925 (0.000##)
1
4. PSI§
.604 (0.005##)
−.955 (0.000##)
−.914 (0.000##)
1
5. TP||
−.408 (0.074)
.929 (0.000##)
.797 (0.000##)
−.850 (0.000##)
1
6. LF¶
−.536 (0.015)
.832 (0.000##)
.722 (0.000##)
−.791 (0.000##)
.875 (0.000##)
1
7. HF**
−.393 (0.086)
.878 (0.000##)
.941 (0.000##)
−.833 (0.000##)
.767 (0.000##)
.574 (0.008##)
1
8. LH/HF
−.127 (0.593)
−.107 (0.654)
−.256 (0.277)
.024 (0.920)
−.009 (0.970)
.275 (0.240)
−.471 (0.036#)
1
9. GARS++
−.025 (0.917)
.065 (0.786)
−.109 (0.649)
−.099 (0.679)
.103 (0.665)
.100 (0.674)
.008 (0.972)
.093 (0.698)
1
10. Age
−.079 (0.742)
−.372 (0.106)
−.296 (0.205)
.219 (0.354)
−.466 (0.038#)
−.380 (0.098)
−.350 (0.131)
.360 (0.119)
.102 (0.668)
1
11. Caffeine intake(cup/day)
.043 (0.856)
.004 (0.987)
−.150 (0.529)
.133 (0.577)
.148 (0.533)
.001 (0.997)
−.026 (0.912)
.020 (0.933)
.344 (0.137)
.026 (0.913)
1
12. Exercise frequency(week)
−.548 (0.012#)
.185 (0.434)
.306 (0.189)
−.260 (0.268)
.143 (0.549)
.072 (0.764)
.284 (0.226)
−.056 (0.816)
.000 (0.999)
.326 (0.161)
−.064 (0.790)
1
13. Drinking frequency(month)
−.510 (0.022#)
.339 (0.144)
.381 (0.098)
−.375 (0.103)
.338 (0.145)
.525 (0.017#)
.292 (0.211)
.097 (0.683)
.327 (0.159)
−.047 (0.844)
−.236 (0.317)
.533 (0.015#)
1
MHR*:Mean Heart Rate; SDNN†:Standard Deviation of Normal to Normal; RMSSD‡:Root Mean Square of Successive Differences between adjacent R-R intervals; PSI§:Physical Stress Index; TP||:Total Power; LF¶:power in Low Frequency range; HF**:power in High Frequency range; GARS++:Global Assessment of Recent Stress; (#, p<0.05, ##, p<0.01)
Table 8
Influencing Factors on SDNN and TP
(n=20)
Variables
Categories
B‡ (SE)
β§
t
p
VIF
F(p)
R(R2)
Adj.R2||
SDNN*
Exercise frequency
−1.749 (2.998)
−.201
−.583
0.568
3.693
4.000 (0.021)
0.718 (0.516)
0.387
Drinking frequency
3.031 (1.758)
0.384
1.724
0.105
1.536
Age
−.561 (0.289)
−.458
−.1944
0.071
1.719
TP†
Exercise frequency
−150.518 (159.930)
−.284
−.941
0.362
3.693
6.378 (0.003)
0.794 (0.630)
0.531
Drinking frequency
254.481 (93.770)
0.528
2.714
0.016#
1.536
Age
−30.643 (15.402)
−.410
−1.990
0.065
1.719
SDNN*:Standard Deviation of Normal to Normal; TP†:Total Power B‡:Unstandardized; β§:Standardized; Adj.R2||: Adjusted R2; (#, p<0.05)
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