Effect of combined use of home blood pressure monitoring and nifedipine on blood pressure compliance and quality of life of patients with essential hypertension

Purpose: To investigate the effect of combination of home blood pressure monitoring (HBPM) and nifedipine on blood pressure compliance and quality of life in patients with essential hypertension. Methods: One hundred and twenty essential hypertension patients admitted to Jiaozuo Coal Industry (Group) Co. Ltd Central Hospital from February 2020 to February 2021 were retrospectively studied. They were equally divided into study group (SG) and control group (COG) according to the order of admission. All patients were treated with nifedipine. Blood pressure was regularly measured in COG patients in the consulting room, while for SG patients, blood pressure was measured at home. Treatment compliance, blood pressure-related indices and quality of life of the two groups were determined. Results: Treatment compliance values of patients in SG at 6 weeks (T2) and 12 weeks (T3) were significantly better than the corresponding values for patients in COG (p < 0.05). The related indices of blood pressure at T2 and T3 were significantly better in SG than in COG (p < 0.05), with higher blood pressure compliance at T2 and T3 in SG (60 and 70 %, respectively) than in COG (p < 0.05). The quality-of-life scores at T3 in SG were significantly higher than those in COG (p < 0.05). Conclusion: The combined use of HBPM and nifedipine improves treatment compliance, enhances the levels of related indices of blood pressure, increases blood pressure compliance, and quality of life of patients with essential hypertension. Therefore, the combined therapy merits further investigation on a larger scale.


INTRODUCTION
In 2019, Cardiovascular Health and Diseases in China reported that there were 330 million Chinese patients with cardiovascular diseases, 245 million of whom had essential hypertension [1]. Thus, the disease constitutes a serious danger to the health and lives of Chinese people. At present, a strategy of drug intervention is used in patients with essential hypertension, in line with the clinical principles of "stable drug efficacy and good tolerance" [2].
The 2018 Chinese Guidelines for the Management of Hypertension indicates that the extents of treatment and control of hypertension in China in 2012 were 40 and 10 % respectively, while the total control from 2012 to 2015 was only 16.8 % [3,4]. This indicates that although there are many types of drugs for treatment of hypertension in China, the blood pressure compliance has not been significantly improved. The 2010 Chinese Guidelines for the Management of Hypertension proposes that effective management is key to prevention of serious cardiovascular and cerebrovascular complications [5,6].
Previous studies have shown that home blood pressure monitoring (HBPM) enhances the accuracy of measurement [7]. Moreover, some studies have shown that HBPM is associated with some advantages such as increasing patients' awareness of the disease, as well as improving their treatment compliance [8]. Presently, not much is known about the therapeutic effectiveness of HBPM. Therefore, the present study was carried out to determine the effect of combined use of home blood pressure monitoring (HBPM) and nifedipine on blood pressure compliance and quality of life of patients with essential hypertension.

General profile of patients
Data for 120 essential hypertension patients admitted to Jiaozuo Coal Industry (Group) Co. Ltd Central Hospital from February 2020 to February 2021 were retrospectively analyzed. The subjects were equally divided into study group (SG, n = 60) and control group (COG, n = 60) according to the order of admission. The study was approved by the ethics committee of Jiaozuo Coal Industry (Group) Co. Ltd Central Hospital (approval no. 20191260), and it was carried out in accordance with the Declaration of Helsinki as revised in 2013 [9]. Signed written informed consents were obtained from the patients and/or their guardians.

Inclusion criteria
Patients in the following categories were enrolled in this study: those who met the World Health Organization (WHO) diagnostic criteria for essential hypertension [10], patients for whom secondary hypertension was excluded by physical examination and laboratory tests, those under the age of 80 years, with basic reading and writing skills, patients who took hypotensive drugs for more than 6 months, with blood pressure between levels 1 and 2 (below clinical blood pressure standards), and patients who used upper arm semi-automatic electronic sphygmomanometer [11] at home with measurement error within ± 0.67 kPa, when compared with the consulting room mercury sphygmomanometer.

Exclusion criteria
The excluded patients were those who had psychiatric problems or inability to communicate with others, patients with severe diseases such as parkinsonism, atrial fibrillation, diabetes mellitus, malignancies, stroke and acute heart failure, as well as hepatic and renal dysfunctions. Moreover, the excluded patients included those who were unable to actively cooperate during the treatment and fill out the questionnaire, and those who withdrew midway from the study.

Withdrawal criteria
The medical records of patients in the following categories were not used for data analysis: those with severe complications and special physiological changes, patients who were adjudged by the doctors to be unsuitable for continued participation in the study, and patients who requested to be withdrawn from the study due to their unwillingness to continue with the clinical trial.

Treatments
All patients were given 20 mg of nifedipine (Hunan Warrant Pharmaceutical Co. Ltd; NMPA approval no. H20084558) once daily. One course of treatment lasted for one month. The patients were treated for a total of 3 courses.

Blood pressure measurement
The blood pressure of each patient in COG was measured regularly in the consulting room. Before the measurement, the patients were allowed to rest and sit for 10 min to eliminate the influence of exercise factors on blood pressure. The patients were instructed to avoid smoking and caffeine intake before blood pressure testing. Cuffs of appropriate sizes were prepared, and the blood pressure of each patient was measured using a standard mercury sphygmomanometer (Jiangsu Yuyue Medical Equipment & Supply Co. Ltd.; NMPA Certified no. 20152070945). During the measurement, the patients were asked to adopt a sitting position with legs naturally on the floor. The lower border of the cuff was 2 cm from the antecubital midline, and the tube was placed on the brachial artery pulse, prior to tightening of the cuffs. Blood pressure in the left upper arm was measured conventionally 3 times, with an interval of 5 min. Patients were kept sitting during this process, and the average of the 3 values was taken as clinical blood pressure. After the measurement, the patients were instructed to come to the consulting room for measurement once every 2 weeks for a total of 12 weeks.
The blood pressure measurement for patients in SG was done at home. Before the measurement, each patient was asked to sit for 10 min, with the cuff at the same level as the heart. The patient sat with back against the seat, and remained still, with legs relaxed. In addition, the patients were instructed not to exercise or consume caffeine before blood pressure testing to avoid the effect of external factors on blood pressure. Measurement was performed 3 times, and the average of the 3 values was recorded. Then, the patients were asked to operate the upper arm semi-automatic electronic sphygmomanometer on site after studying the procedures. Using an assessment scale for the electronic sphygmomanometer, the researchers evaluated whether the patient's operation was appropriate, and corrected any mistakes.
The blood pressure was measured daily at each period (9:00 -10:00 am after breakfast, and 7.00 -9.00 pm after dinner), and the average value of the 6 measurements was recorded. One physician and one nurse were designated to perform routine management of patients in SG and follow up door-to-door once a week in order to assess their performance of HBPM. At the same time, the patients were also required to come to the consulting room for blood pressure measurement once every 2 weeks for 12 weeks. The HBPM was still required on the day of the clinical measurement.

Treatment compliance
This was based on the therapeutic adherence scale for hypertensive patients (TASHP) which was developed for patients with essential hypertension in urban China [12]. Based on the Likert 5-point scoring method, the scale was used to assess medication compliance behavior, adverse medication behavior, daily life management behavior, and smoking and drinking management behavior. The scores ranged from 25 to 125 points for a total of 25 items. The higher the score, the higher the treatment compliance. The data were compared before treatment (T1), 6 weeks after treatment (T2), and 12 weeks after treatment (T3).

Blood pressure-related indices
Before treatment (T1), at 6 weeks (T2) and 12 weeks after treatment (T3), fasting venous blood (5 mL) was collected in the morning and allowed to stand for 30 min. Then, the serum was separated by centrifugation at 3000 rpm. Triglycerides, total cholesterol, and fasting blood glucose (FBG) were measured using an Automatic Biochemical Analyzer (Cobase 411 with matching reagent, NMPA Certified no. 2011 3402843).
The clinical blood pressure values of the patients at T1, T2 and T3 were taken as the standards for calculating the average value. Blood pressure < 140/90 mmHg was set as the qualified standard against which the blood pressure compliance of patients was evaluated.

Quality of life
Quality of life was assessed based on the life scale for hypertensive patients [13]. The scale was used to score physiological symptoms, somatic symptoms, sexual dysfunction, sleep conditions, vitality, anxiety, repression, obsessive-compulsive disorder, interpersonal sensitivity, working state, hostility, ability of daily living, and cognitive ability. Each item was scored 0 -4 points. The higher the total score, the more severe the symptoms of patients. The data were compared before treatment (T1) and at 12 weeks after treatment (T3).

Statistical analysis
In this study, the data were processed using SPSS 20.0, while graphs were prepared with GraphPad Prism7 (GraphPad Software, San Diego, USA). Enumeration data and measurement data are expressed as numbers and percentages (n (%)) and mean ± standard deviation (SD), respectively, and they were compared between the two groups using χ 2 and t-test, respectively. Differences were considered statistically significant at p < 0.05.

General profiles of patients
There were no statistically significant differences in general data between the two groups of patients (p > 0.05). These data are shown in Table 1.

Treatment compliance
Treatment compliance values at T2 and T3 were significantly better in SG than in COG (p < 0.05; Figure 1).

Blood pressure-related indices
The blood pressure-related indices of SG at T2 and T3 were better than those of COG (p < 0.05). The blood pressure compliance values at T2 and T3 for SG reached 60 and 70 % respectively, and were significantly higher than the corresponding values for COG (p < 0.05). These results are presented in Table 2.

Quality-of-life scores
Scores on quality of life at T3 were significantly better in SG than in COG (p < 0.05; Table 3).

DISCUSSION
Essential hypertension, the most common chronic cardiovascular and cerebrovascular disease seen in clinics, often occurs in middleaged and elderly people. It triggers damage to organs such as the heart, brain and kidney, and it causes serious cardiovascular and cerebrovascular complications in patients. Therefore, the clinical treatment of essential hypertension is basically aimed at controlling blood pressure so as to reduce disability and mortality in patients. angiotensin-converting enzyme inhibitors, and angiotensin II receptor inhibitors being the most common. Nifedipine, a calcium channel blocker, is often used for middle-aged and elderly patients, especially those who are accustomed to high sodium diets and alcoholism. Long-term treatment with nifedipine is also effective on atherosclerosis [14]. However, a survey by WHO indicates that patients with chronic diseases often present low treatment compliance. This was confirmed in the 2018 Chinese Guidelines for the Management of Hypertension. From 2012 to 2015, the treatment rate of patients with essential hypertension in China was only 40 %, and the blood pressure compliance was below 20 % [15]. These findings indicate that the use of anti-hypertensive drugs did not produce optimum effects.
The rate of treatment of hypertension increased in all countries worldwide between the 1980s and 1990s, but this rate has decreased in the past two decades. Even in the developed countries like the United States of America and Germany with better anti-hypertensive treatments, blood pressure compliance is not satisfactory: the medication compliance of patients is only 80 %, while the blood pressure compliance in low-and middle-income countries is less than 30 % [16]. This disparity demonstrates a huge gap between developing countries and developed nations. In China, the clinical treatment of essential hypertension focuses on improving the effectiveness of management of the patients. It has been reported that HBPM improves selfmanagement ability of patients which is closely related to treatment compliance. Low treatment compliance of patients with essential hypertension is closely connected with their lifestyles, exercise and eating habits. A study has shown that treatment compliance is also closely associated with the income of patients. In this case, long-term medication resulted in anxiety, thereby seriously affecting effectiveness [17]. Therefore, improvement of the treatment compliance of patients is key to enhancing blood pressure compliance. The results obtained in this study indicate that HBPM fully improved patients' enthusiasm, participation and self-care. This explains why the treatment compliance values in SG at T2 and T3 were significantly better than the corresponding values in COG.
Moreover, HBPM has the advantages of delivering more accurate results and preventing white coat syndrome. It is worth noting that this study also involved door-to-door follow-up by physicians and nurses, and the patients were subjected to external constraints. Due to their enthusiasm for self-test blood pressure, as well as efficient supervision by the research group, the patients paid more attention to their behavior and avoided bad living habits as much as possible. Therefore, the scores on quality of life at T3 in SG were significantly better than the corresponding scores in COG due to changes in the lifestyle of the patients. As a result of these changes, the levels of blood pressure-related indices at T2 and T3 in SG were significantly better than those in COG, and the blood pressure compliance values at T2 and T3 in SG reached 60 and 70 % respectively, which were significantly higher than those in COG, indicating a better treatment effect in SG. In a previous study, it was demonstrated that HBPM enhanced blood pressure compliance in patients [18]. Although regular door-to-door follow-up was not performed in that study, it could not be concluded that the experimental results were unrelated to intervention of the research group. Therefore, the actual effects of HBPM need to be further investigated by prolonging the study time and reducing the intervention.

Limitations of the study
In this study, patients were inevitably subjected to external supervision due to the follow-up survey. Therefore, it is likely that their treatment compliance may be better than that of ordinary patients, thereby affecting their scores in the various scales to some extent. However, the data of the two groups can still be compared. There is need for further investigation of the practical effects of HBPM in studies by prolonging the study time and reducing the intervention of the research group.

CONCLUSION
The combined use of HBPM and nifedipine improve the treatment compliance, enhanced levels of related indices of blood pressure, and increase blood pressure compliance and quality of life of patients with essential hypertension. Therefore, the combined therapy merits further investigation in a larger scale while factoring in the the practical effects of HBPM, prolonging the study time and reducing the intervention of the research group.

Funding
None provided.

Ethical approval
None provided.

Availability of data and materials
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.