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Normal Variations in Blood Pressure in Ambulatory Blood Pressure Measurements



Selcuk Mistik, Kevser Goktas, Demet Unalan, Abdurrahman Oguzhan, Bulent Tokgoz

Euras J Fam Med 2021;10(1):1-6. doi:10.33880/ejfm.2021100101

 

Original Research


ABSTRACT

Aim: Hypertension is very common in primary care patients. The diagnosis of hypertension is made by office measurements and home blood pressure measurements. The aim of this study was to define the normal variation levels of blood pressure in individuals in primary care by using ambulatory blood pressure measurement.

Methods: This study was performed in primary care. Individuals who had no hypertension history were included in the study. Subjects were evaluated by using three office measurements, seven days home blood pressure measurements and 24 hours ambulatory blood pressure measurement. The ambulatory blood pressure gave us the variations in blood pressure values. 

Results: The study started in January 2018 and ended in May 2018. Of the 47 subjects, 70.2% were women and 29.8% were men. The mean age was 41.63±12.00. The most common educational level was elementary school graduates. The most common occupation was housewives. Of the participants, 84.2% were married. At ambulatory blood pressure measurements, 34.0% of the subjects had mean systolic blood pressures 24 hours between 120-129 mmHg. Of the diastolic blood pressure 24 hours mean values, 15.3% had values between 80-89, where 51.0% were between the 71-79 mmHg groups. The mean value of 24 hours variation in systolic blood pressure was 15.75±18.59 (median=11.40, min=8.80, max=106.00). The 24 hours variation in the mean values of diastolic blood pressures was 12.12±10.90 (median=9.70, min=6.80, max=64.00).

Conclusion: The results of this study demonstrated that there were high levels of variations in normal blood pressures, which could show candidates for hypertension.

Keywords: ambulatory monitoring, blood pressure, variability, primary care


Introduction

Hypertension (HT) is an important disease that affects more than a billion people worldwide. Approximately one quarter of the adult population in the world is hypertensive, and in Turkey there is disease in one-third of the population. Today, 25% to 50% of patients are not aware that they have HT disease. Unfortunately, the rate of those whose blood pressure (BP) is under control does not exceed 50%. As can be understood from these data, it is obvious that there are important problems in diagnosing HT and following the compliance with treatment. BP measurement and follow-up of these measurements are important both for correct and early diagnosis, and for monitoring progression (1).

In Turkey under 30 years of age HT prevalence is 5%, whereas HT prevalence seen after the age of sixty goes up to 67-85% (2). According to the World Health Organization (WHO) data, HT prevalence is quite high and ranks first among the preventable causes of death in the world (3). Awareness of HT disease (54.7%) and being under treatment (47.5%) are also very low. Of all the hypertensive patients 28.7%, and 53.9% of those receiving anti hypertensive treatment is not under control (2). Undoubtedly, the most important reason for this large deficit in the treatment of the disease is that the awareness rates are very low. Among the main reasons why HT awareness is at such a low level, the inability of the BP to be adequately and accurately measured.

The importance of a disease for the society is related to the level of incapacity and mortality it causes (3). HT significantly increases the frequency of coronary diseases and vascular diseases (4,5). In order to prevent all these complications, the most important step is to make the diagnosis correctly and early. The most important stage of this is possible by providing the necessary equipment and environmental conditions for detecting the BP and by measuring using a correct technique (6).

The aim of this study was to define the normal variation levels of BP in individuals in primary care by using Ambulatory Blood Pressure Measurement (ABPM).

Methods

Our study was carried out in Erciyes University Medical Faculty Hospital, Department of Family Medicine. Sixty randomly selected individuals from the general population were included in the study. Our study was carried out in accordance with the Helsinki Declaration and informed consent forms were obtained from all patients. Approval was obtained from the Ethics Committee of Erciyes University Faculty of Medicine and financed by Erciyes University Scientific Research Council (ERUBAP, Project No. TTU-2017-7092).This study included all individuals who applied to Erciyes University Faculty of Medicine, Department of Family Practice, between 1 January 2018 and 1 July 2018, who were not diagnosed with HT, did not use any antihypertensive drugs and were willing to participate in the study. Individuals over the age of 18 and who can wear a holter device, regardless of gender difference, were included in the study. A total of 60 individuals were included in the study. During the ambulatory measurement process, 5 individuals did not continue their measurements by saying they felt bad. Four individuals were excluded from the study because the ambulatory measurement results were not sufficiently reliable. Four individuals were excluded from the study because they were newly diagnosed HT patients. A total of 47 people were included in the analysis. Before being included in the study, detailed information was provided about the study and a voluntary consent form was signed.

The questionnaire, which was prepared before the study and recorded demographic features, blood parameters, BP measurements in the office and at home, was filled with the participants. The form included demographic features such as name, surname, age, gender, occupational group, marital status and educational status. It was questioned whether they had additional illnesses, whether they used any medication, what medication they used, if they had been previously diagnosed with HT, whether they had smoking and alcohol habits. Height, weight were questioned and BP values ​​were measured. Body Mass Index (BMI) was calculated.

BMI was calculated by dividing the patient's weight (kg) by the square of the patient's height (m2). Gender as women and men; educational status is illiterate, grouped as primary, secondary, high school, university and above.

Patients were also asked to perform some tests to compare BP and BP measurements as well as parameters related to vascular stiffness determined by central measurement. In these examinations; there were Fasting Plasma Glucose (FPG), triglyceride (TG), total cholesterol (TCHOL), High Density Lipoprotein (HDL), Low Density Lipoprotein (LDL), Blood Urea Nitrogen (BUN), creatinine, Aspartate Aminotranspherase (AST), Alanine Aminotransphe-rase (ALT), Complete Blood Count (CBC), Thyroid Stimulating Hormone (TSH). These values ​​were recorded on the form in which other information of the patient was also available.

The suitability of the data to normal distribution was evaluated by histogram and Q-Q plots and Shapiro-wilk test. Variance homogeneity was tested by Levene test. Mann-Whitney U test and two independent sample t tests were used for quantitative variables in group comparisons. Pearson χ2 analysis was used for comparison of categorical data. Bland Altman graphics and Passing Bablok regression analysis were used for method comparisons. Systematic error and proportional error were evaluated considering the confidence intervals of the estimated regression coefficients. The relationship between quantitative data was evaluated by Spearman correlation analysis. The data were performed in Turcosa (Turcosa Ltd Co) statistical software. Significance level was accepted as p <0.05.

Results

The study was conducted with 47 people who did not have HT disease and did not take hypertensive medication. Thirty-three (70.2%) of the participants were female and 14 (29.8%) were male. The mean age of all patients was 41.63±12.00 and the minimum age was 19 and the maximum age was 66. The socio-demographic data of the participants are shown in Table 1.

Table 1. Socio-demographic properties

Groups

n

%

Gender

Men

14

29.8

Women

33

70.2

Body Mass Index

≤25

19

40.4

25-30

16

34.0

≥30

12

25.6

Job

Student

3

6.4

Housewife

22

46.8

Clerk

10

21.3

Employee

5

10.6

Retired 

4

8.5

Others

3

6.4

Smoking

Yes

2

4.2

No

45

95.8

Additional Disease

Yes

13

27.7

No

34

72.3

Marital Status

Married

41

87.2

Single

6

12.8

 

While 83% (n=39) of the participants in our study consisted of normotensive individuals, white coat HT was detected in 13% (n=6) of the participants. Masked HT was observed in 4% of the participants (n=2) (Table 2). The correlation of the participants' mean BP with age, BMI, TG, TCHOL, HDL, LDL is shown in Table 3.

Table 2. BP Classification

 

OBPM (mmHg)

ABPM (mmHg)

n (%)

Normal BP

   

39 (83)

Hypertensive

≥140 or ≥ 90

≥135 or ≥ 85

0 (0)

White coat HT

≥140 or ≥ 90

 

6 (13)

Masked HT

 

≥135 or ≥ 85

2 (4)

OBPM: office blood pressure measurement, ABPM:, ambulatory blood pressure measurement

The mean value of twenty four hours variation in systolic blood pressure (SBP) was 15.75±18.59 (median=11.40, min=8.80, max=106.00). The 24 hours variation in the mean values of diastolic blood pressures (DBP) was 12.12±10.90 (median=9.70, min=6.80, max=64.00).

In addition, the relationship between variability in BP and demographic data of participants and BPs was examined. No statistically significant correlation was found between age, gender, BMI, smoking and laboratory parameters FPG, TG, TCHOL, HDL, LDL, TSH and variability in BP. Again, a positive correlation was found between diastolic Home Blood Pressure Measurement (HBPM) and diastolic ABPM ​​(0.339*, 0.324*). There was no significant relationship between other BP measurements and variability in BP. 

Table 3. Correletions with mean blood pressure values

 

ABPM

HBPM

OBPM

 

SBP

DBP

SBP

DBP

SBP

DBP

Age

0.250

0.486**

0.546**

0.502**

0.346*

0.419**

BMI

0.114

0.279

0.423**

0.391**

0.471**

0.470**

TG

0.94

0.388**

0.333*

0.477**

0.335*

0.477**

Tchol

-0.140

0.71

0.054

0.105

0.053

0.231

HDL

-0.262

-0.335*

-0.363*

-0.420**

-0.397**

-0.339**

LDL

0.051

0.179

0.260

0.253

0.252

0.370*

*= p

In the evaluation of SBP and DBP measurements, Bland-Altman graphs and Passing-Bablok regression analysis were used for comparison of ABPM method and home, office and central measurement methods and compliance analysis.

According to Passing-Bablok regression analysis and Bland-Altman charts: 

The equation of y = 0.38 + 1.02 x (Intersection Confidence Interval: -32.17 / 31.74, Slope Confidence Interval: 0.74 / 1.32) was obtained (Figure 1, Table 4). No systematic or proportional systematic errors were observed between the methods. No deviation from linearity was observed between the methods (p>0.05). When the interclass correlation coefficients were analyzed, it was seen that there was a very weak fit between the two measurements. However, this was not statistically significant (p=0.133). When comparing the two methods in Bland-Atman graphs, it was determined that the BP values ​​obtained were on average 4.8 lower (Figure 2).

Figure 1. Passing-Bablok regression graph for comparison of home and ambulatory systolic blood pressure measurement techniques

Table 4. Passing-Bablok regression data and compliance statistics regarding the comparison of home and ambulatory systolic blood pressure measurement techniques

Parameter Estimates

Passing- Bablok

Compliance Statistics

B0

B1

ICC

CCC

Qoefficient

0.380

1.027

0.164

0.155

%95 CI

-32.127/31.740

0.745/1.324

-0.126/0.429

-0.077/0.371

Comment

No systemic error

No proportional error

Very weak compliance

Very weak compliance

CI: confidence interval, ICC: interclass correlation coefficient, CCC: compliance correlation coefficient

Figure 2. Bland-Altman graph for comparison of home and ambulatory systolic blood pressure measurement techniques

Discussion

The gold standard diagnosis method in HT is accepted as ABPM internationally. In addition, it was shown that patients with HBPM had less discomfort and were more compatible with treatment. Patient compliance was found to be 92% with HBPM and 74% with OBPM (7). In the OlmeTel (Olmesartan Telemonitoring Blood Pressure) study by Ewald et al. (8), HBPM was superior in terms of patient compliance and BP regulation. However, although such publications are available, ABPM continues to be used as the most reliable method in the world.

In the work of Botomino et al. (9), they investigated the effect of white coat on BP and in this context, they compared OBPM, HBPM, ABPM. Twenty two of the 50 patients included in the study were reported to be using antihypertensive therapy. In all patients included in the study, OBPM was found to be significantly higher in SBP and DBP compared to ABPM (p=0.032 for SBP, p=0.018 for DBP). In addition, patients who use antihypertensive drugs have been reported to have higher rates of increase in SBP and DBP than those who do not. They determined OBPM significantly higher than that of HBPM (p<0.001, for both systolic and diastolic). Again, in this study, the rate of white coat HT was found to be 10.7% in healthy individuals who did not receive antihypertensive treatment, while the rate of masked HT was reported as 17.9%.

In a study, it was reported that BP variability increased progressively with an increase in mean BP (10). In their study on 8938 patients, they examined the relationship between 24-hour BP variability and total mortality, mortality due to cardiovascular diseases and mortality not related to cardiovascular diseases. In this study, it was observed that when the variability value in the mean SBP exceeds 12.5 mmHg, it was significantly increased in all three mortalities. In cases where the variability value in the average DBP exceeds 9.3 mmHg, mortality values ​​also increased significantly (11). In a study conducted on 156 patients, the mean variability value in the mean SBP was found to be 9.6±2 mmHg in 24-hour ABPM in healthy adults, while the mean variability value in the average DBP was 8±1.7 mmHg (12). In our study, the variability value in the average SBP was determined as 12.2±2.6 mmHg, while in the DBP, this value was determined as 9.4±2.4 mmHg. Abramson et al. (10) compared the BMI and blood leptin levels of healthy adults and standard deviation values ​​in SBP and DBP and found a statistically significant correlation between these values. However, in our study, no significant correlation was found between standard deviation values ​​and age, BMI, gender, blood lipid profile, FPG, and smoking.

It may be more convenient to evaluate normal variations of BP with more individuals involved in the study. This is a limitation of our study.

Conclusion

The results of this study demonstrated us that there were high levels of variations in normal BPs, which could show candidates for HT. It may be beneficial for patients if family physicians could evaluate variations in BP during their daily practice.

References

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How to cite: Mistik S, Goktas K, Unalan D, Oguzhan A, Tokgoz B. Normal variations in blood pressure in ambulatory blood pressure measurements. Euras J Fam Med 2021;10(1):1-6. doi:10.33880/ejfm.2021100101.


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