A total of 318 essential hypertensive patients were included in the study; 66 (20.75%) were classified as dippers, 140 (44.03%) as non-dippers, and 112 (35.22%) as reverse dippers. Compared to those of the dippers, the non-dippers and reverse dippers were more likely to be older (57.00 ± 10.48 vs. 60.10 ± 14.96 vs. 65.96 ± 13.97 years, P < .001). There were no significant differences in sex, body mass index (BMI), or the use of angiotensin-converting enzyme inhibitors/angiotensin receptor blockers, β-blockers, calcium channel blockers or diuretics (all P > .05).
The nocturnal SBP (122.20 ± 7.46 vs. 130.21 ± 10.57 vs. 139.21 ± 13.89 mm Hg) and
nocturnal DBP (73.26 ± 8.38 vs. 76.71 ± 9.85 vs. 77.04 ± 10.96 mm Hg) gradually increased in the dipper, non-dipper, and reverse dipper groups (all P < .05).
Conversely, the 24-hour DBP (81.73 ± 9.22 vs. 80.43 ± 9.59 vs. 76.18 ± 10.66 mm Hg), daytime SBP (141.82 ± 8.28 vs. 135.85 ± 10.35 vs. 131.70 ± 13.20 mm Hg), daytime DBP (84.62 ± 9.48 vs. 81.66 ± 9.75 vs. 75.84 ± 10.92 mm Hg) and nocturnal SBP decline (13.79 ± 3.28 vs. 4.15 ± 3.00 vs. -5.80 ± 4.37%) gradually decreased from the dipper, non-dipper, and reverse dipper groups (all P < .001). The 24-hour SBP was similar among the three groups (P = .111). The baseline characteristics and ambulatory BP parameters of the dipper, non-dipper, and reverse dipper groups are summarized in Table 1.
Table 1
Baseline characteristics and ambulatory BP parameters of the subjects
| Dipper | Non-dipper | Reverse dipping | χ2/F/H | P |
N (%) | 66(20.75) | 140(44.03) | 112(35.22) | | |
Age (years) | 57.00 ± 10.48 | 60.10 ± 14.96& | 65.96 ± 13.97*# | 10.074 | 0.000 |
Female n (%) | 29(43.94) | 46(32.86) | 47(41.96) | 3.277 | 0.194 |
BMI (kg/m2) | 25.46(24.04 ~ 27.48) | 25.70(23.60 ~ 28.38) | 25.74(23.88 ~ 28.05) | 0.411 | 0.814 |
Medications n (%) |
ACEI/ARB n (%) | 21(31.82) | 49(35.00) | 33(29.46) | 0.883 | 0.643 |
β-Blocke n (%) | 12(18.19) | 22(15.71) | 18(16.07) | 0.210 | 0.900 |
CCBs n (%) | 32(48.49) | 71(50.71) | 59(52.68) | 0.298 | 0.862 |
Diuretic n (%) | 4(6.06) | 8(5.71) | 7(6.25) | 0.033 | 0.984 |
Ambulatory BP parameters |
24hr SBP (mmHg) | 137.14 ± 8.03 | 134.51 ± 10.26 | 133.59 ± 13.14 | 2.216 | 0.111 |
24hr DBP(mmHg) | 81.73 ± 9.22 | 80.43 ± 9.59 | 76.18 ± 10.66*# | 8.426 | 0.000 |
Daytime SBP(mmHg) | 141.82 ± 8.28 | 135.85 ± 10.35& | 131.70 ± 13.20*# | 17.369 | 0.000 |
Daytime DBP (mmHg) | 84.62 ± 9.48 | 81.66 ± 9.75 | 75.84 ± 10.92*# | 18.145 | 0.000 |
Night-time SBP(mmHg) | 122.20 ± 7.46 | 130.21 ± 10.57& | 139.21 ± 13.89*# | 48.850 | 0.000 |
Night-time DBP (mmHg) | 73.26 ± 8.38 | 76.71 ± 9.85& | 77.04 ± 10.96* | 3.433 | 0.034 |
Percentage of n-SBP decline (%) | 13.79 ± 3.28 | 4.15 ± 3.00& | -5.80 ± 4.37*# | 639.20 | 0.000 |
& compared with dipper group P < 0.05, * compared with dipper group P < 0.05, # compared with nondipper group P < 0.05, BMI Body mass index, ACEI Angiotensin-converting enzyme inhibitor, ARB Angiotensin-converting enzyme receptor blocker, CCBs Calcium channel blocker, SBP Systolic blood pressure, DBP Diastolic blood pressure. |
Comparison of Holter recording and echocardiographic parameters for dipper, non-dipper, and reverse dipper blood pressure measurements
As shown in Fig. 1, DC was lowest in the reverse dipper group, followed by the nondipper and dipper groups (8.07 ± 1.79 vs. 6.65 ± 1.95 vs. 6.46 ± 2.06 ms, P < .001) (Fig. 1A). Conversely, the AC gradually decreased (-7.80 ± 1.73 vs. -6.55 ± 1.95 vs. -6.32 ± 2.02 ms, P < .001) (Fig. 1B).
The average HR (70.18 ± 7.71 vs. 75.16 ± 9.33 vs. 73.39 ± 8.98 bpm, P = .001) and the slowest HR (53.15 ± 4.80 vs. 55.02 ± 8.06 vs. 56.14 ± 7.39 bpm, P = .031) were greater in the non-dipper and reverse dipping groups, respectively, than in the dipper group.
The HRV indices SDNN (125.36 ± 21.22 vs. 114.99 ± 32.79 vs. 105.08 ± 30.01 ms, P < .001), SDANN [126.45 (107.25 ~ 149.23) vs. 114.45 (91.65 ~ 134.38) vs. 113.50 (84.30 ~ 146.90) ms, P = .013], and PNN50 [6.15 (4.00 ~ 10.13) vs. 4.00 (1.83 ~ 8.08) vs. 4.40 (1.85 ~ 6.70), P = .002] gradually decreased in the non-dipper and reverse dipper groups. However, the RMSSD did not significantly differ among the three groups.
In terms of echocardiographic parameters, the LVEF was lower in the non-dipper and reverse dipper groups than in the dipper group (65.77 ± 4.90 vs. 63.78 ± 5.21 vs. 64.08 ± 4.89 ms, P = .020). However, RAd, LAd, LVESd, and LVEDd did not significantly differ between dippers and non-dippers.
The Holter recording and echocardiographic parameters of the dipper, non-dipper, and reverse dipper groups are summarized in Table 2.
Table 2
Comparison of 24-hr ambulatory electrocardiographic and echocardiographic variables between dipper ,non-dipper and reverse dipper groups.
| Dipper(n = 66) | Non-dipper (n = 140) | Reverse dipper (n = 112) | F/H | P |
Deceleration and Acceleration capacities |
Deceleration capacity (ms) | 8.07 ± 1.79 | 6.65 ± 1.95& | 6.46 ± 2.06* | 15.153 | 0.000 |
Acceleration capacity (ms) | -7.80 ± 1.73 | -6.55 ± 1.95& | -6.32 ± 2.02* | 13.231 | 0.000 |
Heart rate variability |
Average HR (bpm) | 70.18 ± 7.71 | 75.16 ± 9.33& | 73.39 ± 8.98* | 7.055 | 0.001 |
Slowest HR (bpm) | 53.15 ± 4.80 | 55.02 ± 8.06 | 56.14 ± 7.39* | 3.528 | 0.031 |
Fastest HR (bpm) | 106.33 ± 12.90 | 111.59 ± 16.82 | 107.78 ± 109.16 | 2.849 | 0.059 |
SDNN (ms) | 125.36 ± 21.22 | 114.99 ± 32.79& | 105.08 ± 30.01*# | 9.055 | 0.000 |
SDANN (ms) | 126.45(107.25 ~ 149.23) | 114.45(91.65 ~ 134.38)& | 113.50(84.30 ~ 146.90)* | 8.745 | 0.013 |
RMSSD (ms) | 58.00(30.80 ~ 77.60) | 49.60(31.93 ~ 76.07) | 48.05(31.33 ~ 80.40) | 1.035 | 0.596 |
PNN50 (%) | 6.15(4.00 ~ 10.13) | 4.00(1.83 ~ 8.08)& | 4.40(1.85 ~ 6.70)* | 12.481 | 0.002 |
Echocardiography |
RAd (ms) | 33.70 ± 3.98 | 33.52 ± 4.80 | 32.63 ± 3.59 | 1.834 | 0.161 |
LAd (ms) | 35.55 ± 5.24 | 34.94 ± 5.40 | 34.67 ± 4.89 | 0.596 | 0.552 |
LVESd (ms) | 29.24 ± 3.55 | 30.68 ± 3.92 | 29.77 ± 3.59 | 3.849 | 0.120 |
LVEDd (ms) | 46.12 ± 3.85 | 47.22 ± 4.71 | 46.15 ± 4.61 | 2.250 | 0.107 |
LVEF(%) | 65.77 ± 4.90 | 63.78 ± 5.21& | 64.08 ± 4.89* | 3.972 | 0.020 |
& compared with dipper group P < 0.05, * compared with dipper group P < 0.05, # compared with nondipper group P < 0.05, BPM Beat per min, HR Heart rate, SDNN Standard deviation of NN intervals, SDANN standard deviation of normal-to-normal intervals, RMSSD Root mean square of successive differences, PNN50 The mean number of times in full course in which the change in successive normal sinus intervals exceeds 50 ms, RAd Right atrial diameter, LAd Left atrial diameter, LVESd Left ventricular end-systolic diameter, LVEDd Left ventricular end-diastolic diameter, LVEF Left ventricular ejection fraction. |
Correlation analysis among ABPM parameters, heart rate variability, echocardiographic variables, heart rate deceleration capacity and acceleration capacity
The results showed that age was negatively correlated with deceleration capacity (r = − .222, p < .001) and positively correlated with acceleration capacity (r = .255, p < .001). Additionally, 24-h DBP and daytime DBP were positively correlated with deceleration capacity and negatively correlated with acceleration capacity. Conversely, night-time SBP, similar to age, was negatively correlated with deceleration capacity and positively correlated with acceleration capacity (all P < .001). Furthermore, the percentage of n-SBP decrease was found to be positively correlated with deceleration capacity (r = .307, p < .001; Fig. 2A) and negatively correlated with acceleration capacity (r = − .303, p < .001; Fig. 2B).
Moreover, the SDNN showed a negative correlation with deceleration capacity (r = − .194, p = .021) and a positive correlation with acceleration capacity (r = .251, p = .003). The average HR and Slowest HR were also negatively correlated with deceleration capacity and positively correlated with acceleration capacity; correlation analysis results are presented in Table 3.
Table 3
Correlation analysis among 24-hr ambulatory BP, echocardiographic recordings, acceleration capacity, and deceleration capacity.
| Deceleration capacity | Acceleration capacity |
| r | p | r | p |
Age | -0.222 | 0.000 | 0.255 | 0.000 |
24-h SBP | 0.021 | 0.708 | 0.001 | 0.986 |
24-h DBP | 0.187 | 0.000 | -0.199 | 0.000 |
Daytime SBP | 0.093 | 0.099 | -0.070 | 0.216 |
Daytime DBP | 0.214 | 0.000 | -0.225 | 0.000 |
Night-time SBP | -0.186 | 0.001 | 0.200 | 0.000 |
Night-time DBP | 0.073 | 0.192 | -0.074 | 0.185 |
Percentage of n-SBP decline | 0.307 | 0.000 | -0.303 | 0.000 |
SDNN | 0.389 | 0.000 | -0.396 | 0.000 |
Average HR | -0.216 | 0.000 | 0.195 | 0.000 |
Slowest HR | -0.307 | 0.000 | 0.300 | 0.000 |
Fastest HR | -0.019 | 0.731 | 0.022 | 0.701 |
RAd | 0.016 | 0.778 | -0.013 | 0.811 |
LAd | 0.023 | 0.645 | -0.033 | 0.561 |
LVESd | -0.067 | 0.236 | 0.054 | 0.341 |
LVEDd | -0.028 | 0.642 | 0.017 | 0.757 |
LVEF | 0.078 | 0.163 | -0.076 | 0.178 |
SBP Systolic blood pressure, DBP Diastolic blood pressure, SDNN Standard deviation of NN intervals, HR Heart rate, RAd Right atrial diameter, LAd Left atrial diameter, LVESd Left ventricular end-systolic diameter, LVEDd Left ventricular end-diastolic diameter, LVEF Left ventricular ejection fraction. |
Relationship between the percentage of nocturnal SBP decrease and DC/AC
We used multiple linear regressions to analyze the relationships between the percentage of nocturnal SBP decrease and DC (Table 4), AC (Table 5). Correlation analysis revealed that the models included DC/AC, age, average HR, slowest HR, SDNN, DC (β = 0.785, P = .001) and SDNN (β = 0.040, P = .024), which were positively associated with nocturnal SBP decline. On the other hand, AC (β = -0.753, P = .002) and age (β= -0.118, P < .001) were negatively associated with nocturnal SBP decrease.
Table 4
The relationships between percentage of nocturnal -SBP decline and deceleration capacity.
| B | SE | β | t | P |
Deceleration capacity | 0.785 | 0.231 | 0.199 | 3.405 | 0.001 |
Age | -0.118 | 0.033 | -0.208 | -3.630 | 0.000 |
Average HR | -0.063 | 0.073 | -0.070 | -0.856 | 0.393 |
Slowest HR | 0.044 | 0.097 | 0.040 | 0.455 | 0.649 |
SDNN | 0.040 | 0.018 | 0.151 | 2.268 | 0.024 |
B the unstandardized beta coefficient, SE standard error, β the standardized coefficient, HR, heart rate, SDNN standard deviation of NN intervals. |
Table 5
The relationships between percentage of nocturnal -SBP decline and acceleration capacity.
| B | SE | β | t | P |
Acceleration capacity | -0.753 | 0.237 | -0.187 | -3.161 | 0.002 |
Age | -0.117 | 0.033 | -0.206 | -3.557 | 0.000 |
average HR | -0.067 | 0.073 | -0.076 | -0.922 | 0.357 |
Slowest HR | 0.045 | 0.098 | 0.040 | 0.456 | 0.648 |
SDNN | 0.040 | 0.018 | 0.153 | 2.281 | 0.023 |
Note: B, the unstandardized beta coefficient; SE standard error; β, the standardized coefficient; HR, heart rate;SDNN, standard deviation of NN intervals. |
Multivariate logistic regression analysis for the circadian BP pattern
To determine the independent risk factors for non-dipper status, multivariate logistic regression analysis was performed in our study. According to the deceleration capacity model, deceleration capacity [OR (95% CI): 0.705 (0.594–0.836), p < .001], age [OR (95% CI): 1.039 (1.015–1.065), p = .002] and average HR (95% CI): 1.114 (1.052–1.181), p < .001] were identified as independent risk factors for BP non-dipper status (Table 6). Similarly, in the acceleration capacity model, we observed that acceleration capacity [OR (95% CI): 1.357 (1.141–1.614), p = .001], age [OR (95% CI): 1.039 (1.014–1.064), p = .002] and average HR [OR (95% CI): 1.114 (1.052–1.179), p < .001] were also independent risk factors for BP non-dipper status (Table 7).
Table 6
Multivariate logistic regression analysis for circadian BP pattern
| B | SE | Wald | P | OR(95%CI) |
Deceleration capacity | -0.350 | 0.087 | 16.010 | 0.000 | 0.705(0.594–0.836) |
Age | 0.039 | 0.012 | 9.784 | 0.002 | 1.039(1.015–1.065) |
average HR | 0.108 | 0.030 | 13.435 | 0.000 | 1.114(1.052–1.181) |
Slowest HR | -0.084 | 0.043 | 3.793 | 0.051 | 0.920(0.845–1.001) |
SDNN | -0.009 | 0.006 | 2.095 | 0.148 | 0.991(0.979–1.003) |
ORs for continuous variables = odds ratio for an increase in 1 unit. Values in bold indicate statistical significance (p < .05). B logistic coefficient, CI 95% confidence interval, HR, heart rate, SDNN standard deviation of RR intervals. |
Table 7
Multivariate logistic regression analysis for circadian BP pattern
| B | SE | Wald | P | OR(95%CI) |
Acceleration capacity | 0.305 | 0.088 | 11.906 | 0.001 | 1.357(1.141–1.614) |
Age | 0.038 | 0.012 | 9.505 | 0.002 | 1.039(1.014–1.064) |
average HR | 0.108 | 0.029 | 13.591 | 0.000 | 1.114(1.052–1.179) |
Slowest HR | -0.079 | 0.042 | 3.503 | 0.061 | 0.924(0.850–1.004) |
SDNN | -0.009 | 0.006 | 2.158 | 0.142 | 0.991(0.979–1.003) |
ORs for continuous variables = odds ratio for an increase in 1 unit. Values in bold indicate statistical significance (p < .05). B logistic coefficient, CI 95% confidence interval, HR, heart rate, SDNN standard deviation of RR intervals. |
ROC curve for predicting the circadian rhythm of blood pressure with DC and AC
ROC analysis was also conducted to evaluate the ability of DC/AC to predict the circadian rhythm of blood pressure (Fig. 3). Patients were divided into two groups based on dipping (nocturnal SBP decline ≥ 10%) or non-dipping (nocturnal SBP decline < 10%). The area under the curve (AUC) for DC in predicting the circadian rhythm of blood pressure was 0.711. With a cutoff of 7.75 ms, the sensitivity and specificity were 73.4% and 66.7%, respectively (Fig. 3A). Similarly, the AUC for AC in predicting the circadian rhythm of blood pressure was 0.697. With a cutoff of -7.05, the sensitivity and specificity of AC were 65.1% and 71.2%, respectively (Fig. 3B).