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Factors associated to treatment adherence in elderly people with hypertension: A cross-sectional study in Ho Chi Minh city

Open AccessPublished:June 23, 2022DOI:https://doi.org/10.1016/j.cegh.2022.101099

      Abstract

      Background

      Treatment of hypertension should be continuous, and patients should be closely monitored for treatment adherence. However, non-compliance still exists globally. This study aimed to determine treatment adherence among patients aged ≥60 years with hypertension and its associated factors in an urban district of Ho Chi Minh City, Vietnam.

      Methods

      A cross-sectional study evaluated treatment adherence in two areas: medication and non-pharmacological adherence. Medication adherence was measured using the 8-item Morisky Medication Adherence Scale. Non-pharmacological adherence was based on the Ministry of Health guidelines for hypertension treatment and assessed by lifestyle changes, including smoking cessation, alcohol consumption restriction, reduced salt intake, increased physical activity, and regular follow-up visits.

      Results

      A total of 537 people participated in the study, of whom females accounted for the majority (63.7%), and patients aged 60–70 years old accounted for 50%. The proportion of patients with medication adherence was 11.7%. The percentages of patients who adhered to non-smoking and limited alcohol intake were 93.5% and 92.9%, respectively. A total of 76.9% of patients underwent regular check-ups. The proportion of patients who adhered to moderate and high levels of physical activity was 64.3%. Patients who were compliant with salt intake reduction accounted for 63.1%. Factors related to antihypertensive drug adherence included disease duration and chronic comorbidities. Factors associated with non-drug adherence included health insurance, comorbidities, and nutritional status.

      Conclusions

      Intervention programs to increase hypertension treatment adherence among elderly patients should focus on educating drug adherence and salt reduction, especially in long-standing and comorbidities patients.

      Keywords

      1. Introduction

      Hypertension is a major cause of premature death worldwide. The 2019 World Health Organization (WHO) report estimated that 1.13 billion people worldwide suffer from high blood pressure, two-thirds of whom live in low- and middle-income countries.
      • World Health Organization WHO
      Hypertension.
      Vietnam is currently facing an increasing number of non-communicable diseases (NCDs), including hypertension. From 2009 to 2019, the prevalence of hypertension in Vietnam increased by 16.4% and became one of the ten leading causes of morbidity and mortality in Vietnam.
      Despite the increasing incidence of hypertension, rates of awareness, treatment, and controlled BP are low, especially in low- and middle-income countries.
      • Mills K.T.
      • Stefanescu A.
      • He J.
      The global epidemiology of hypertension.
      According to the 2019 WHO report, less than 20% of patients with hypertension have controlled BP.
      • World Health Organization WHO
      Hypertension.
      A study in sub-Saharan Africa showed that only 7% of patients treated for hypertension achieved BP control.
      • Ataklte F.
      • Erqou S.
      • Kaptoge S.
      • Taye B.
      • Echouffo-Tcheugui J.B.
      • Kengne A.P.
      Burden of undiagnosed hypertension in sub-saharan Africa: a systematic review and meta-analysis.
      According to a 2012 national survey in Vietnam, only 29.6% of patients with hypertension received treatment and only 10.7% achieved their target BP.
      • Son P.T.
      • Quang N.N.
      • Viet N.L.
      • et al.
      Prevalence, awareness, treatment and control of hypertension in Vietnam-results from a national survey.
      Reasons for poor BP control included the absence of treatment guidelines or non-compliance with the physician's instructions for medication usage or lifestyle changes.
      • Myat A.
      • Redwood S.R.
      • Qureshi A.C.
      • Spertus J.A.
      • Williams B.
      Resistant hypertension.
      Treatment of hypertension should be continuous, and patients should be closely monitored for treatment adherence. However, non-compliance still exists globally (e.g., 41.6% in the United Kingdom and 31.5% in the Czech Republic).
      • Gupta P.
      • Patel P.
      • Strauch B.
      • et al.
      Risk factors for nonadherence to antihypertensive treatment.
      In Vietnam, a cross-sectional study was performed on 783 patients aged ≥60 years at District 7 Hospital, the adherence rate for drug therapy was only 25.0%.
      • Mai Tranh Bui Thi
      • Minh Duc Nguyen
      • Nguyen Nguyen Do
      Adherence to antihypertensive medication in elderly hypertensive patients.
      Factors related to compliance were health insurance, marital status, age, accompanying chronic illnesses, doctor's consultation, and application of non-drug measures. According to a study in 2017 in Tien Hai district, Thai Binh province, the compliance rate of hypertensive patients was only 28.4%.
      • Hanh Tran Thi My
      Evaluation of Intervention Results to Improve Blood Pressure Monitoring Practice and Treatment Adherence in Hypertensive People over 50 Years Old in Tien Hai district, Thai Binh Province, Ph.D of Public Health.
      Another study showed that an unhealthy lifestyle, including salty food intake (51.7%), alcohol consumption (22.6%), cigarette smoking (17.4%), and a lack of physical activity (60.0%), was an obstacle to controlling hypertension.
      • My Hanh Nguyen Thi
      • Duyen Nguyen Thi My
      • Khanh Ly Huy
      • et al.
      Investigation of the relationship between medication adherence and blood pressure control in hypertensive patients on outpatient treatment.
      District 10 (in Ho Chi Minh City) is densely populated, with diverse levels of education, and working, making it difficult to address health status and compliance. In 2017, the prevalence of adults with hypertension in the district was 33.8%. In the elderly (≥60 years), this rate was up to 66.8%.
      • Hanh Vo Thi Xuan
      • Cao Nguyen Hoai Thuong
      • Phan Thi Kim Hoang
      • et al.
      The prevalence of hypertension and diabetes through a survey on a representative sample in the inner-city district of Ho Chi Minh City.
      However, there were no data on how these patients were treated for hypertension or whether they achieved their target BP. Therefore, we asked the following research questions: What is the rate of treatment adherence in people aged ≥60 years with hypertension in District 10, Ho Chi Minh City? What factors affect patient adherence to treatment? The results of this study will form the basis for intervention programs to improve treatment adherence and help patients maintain target BP levels, thereby improving their quality of life.

      2. Methods

      2.1 Study design

      A cross-sectional study of hypertensive patients aged ≥60 years was conducted from November to December 2020 in District 10, Ho Chi Minh City (HCMC), Vietnam.

      2.2 Sample size

      This study used a formula to estimate sample size for a one-sample comparison of proportion to the hypothesized value where p = 28.4%,
      • Hanh Tran Thi My
      Evaluation of Intervention Results to Improve Blood Pressure Monitoring Practice and Treatment Adherence in Hypertensive People over 50 Years Old in Tien Hai district, Thai Binh Province, Ph.D of Public Health.
      accuracy of measurement = 5%, and estimated response rate = 80%, using a 0.05 significance level test. At least 392 people were required for the survey; the study included 537 people.

      2.3 Sampling

      A judgment sample was used. The enumerators visited all patients aged ≥60 years in each ward according to their listed address (taken from the census source of the District 10 Health Office) to determine, by interview, if they had hypertension.
      All patients aged ≥60 years previously diagnosed with hypertension for more than 3 months at the time of the study were eligible for inclusion. Individuals who had declining cognition were excluded.

      2.4 Data collection

      Medication adherence was assessed using the 8-item Morisky Medication Adherence Scale (MMAS-8).
      • Morisky D.E.
      • DiMatteo M.R.
      Improving the measurement of self-reported medication nonadherence: response to Authors.
      Morisky scale has been validated and found to be reliable in many countries. In Vietnam, it has been translated and widely used in many studies. The scale is based on the patients’ self-response and consists of eight questions: seven items with yes or no responses, and one item with a 5-point Likert scale response option. The total score ranges from 1 to 8, and patients with adherence scores of 6 or more were considered adherent.
      Non-pharmacological adherence was based on the Ministry of Health (MOH) guidelines for treating hypertension with lifestyle changes, including smoking cessation, alcohol and salt intake reduction, and increased physical activity
      The Ministry of Health
      Decision No. 5904/QD-BYT Dated December 20, 2019 on the Issuance of Professional Documents "Guidelines for Diagnosis, Treatment and Management of a Number of Non-communicable Diseases at Commune Health Stations.
      as follows:
      • -
        Patients were considered compliant with follow-up if they received a follow-up examination for hypertension in the past 3 months, according to their doctor's instructions, or an early/delayed examination within 3 days of the original appointment.
        The Ministry of Health
        Decision No. 5904/QD-BYT Dated December 20, 2019 on the Issuance of Professional Documents "Guidelines for Diagnosis, Treatment and Management of a Number of Non-communicable Diseases at Commune Health Stations.
      • -
        Patients were considered compliant with smoking if they did not smoke or completely quit smoking (including e-cigarettes) in the past three months.
        The Ministry of Health
        Decision No. 5904/QD-BYT Dated December 20, 2019 on the Issuance of Professional Documents "Guidelines for Diagnosis, Treatment and Management of a Number of Non-communicable Diseases at Commune Health Stations.
      • -
        Patients were considered compliant with alcohol consumption if they drank ≤2 standard drinks/day (men) or ≤ 1 standard drink/day (women), and their weekly total was ≤10 standard drinks/week (men) or ≤ 5 standard drinks/week (women).
        The Ministry of Health
        Decision No. 5904/QD-BYT Dated December 20, 2019 on the Issuance of Professional Documents "Guidelines for Diagnosis, Treatment and Management of a Number of Non-communicable Diseases at Commune Health Stations.
      • -
        Patients were considered compliant with salt reduction if they used <5 g salt/day (corresponding to < 1.9 g sodium (Na)/day).
        The Ministry of Health
        Decision No. 5904/QD-BYT Dated December 20, 2019 on the Issuance of Professional Documents "Guidelines for Diagnosis, Treatment and Management of a Number of Non-communicable Diseases at Commune Health Stations.
        Daily sodium intake was calculated based on the food frequency questionnaire (FFQ) of high-salt foods according to the formula: [portion size in grams] × [reported consumption frequency (converted to times per day)] × [nutrient per gram].
        • Kusama K.
        • Le Duc Son Nguyen Trung
        • Hanh Tran Thi Minh
        • et al.
        Reproducibility and validity of a food frequency questionnaire among Vietnamese in Ho Chi Minh city.
        This is the first FFQ specifically developed and validated for the assessment of dietary intakes of major nutrients by Vietnamese adults.
      • -
        Physical activity compliance was assessed using the International Physical Activity Questionnaire-Short Form (IPAQ-SF),
        • Craig C.L.
        • Marshall A.L.
        • Sjöström M.
        • et al.
        International physical activity questionnaire: 12-country reliability and validity.
        which is a suitable instrument for monitoring habitual physical activity in older Vietnamese adults.
        • Tran D.V.
        • Andy H.L.
        • Thuy B.A.
        • Nguyen C.T.
        • Hoang D.V.
        Reliability and validity of the international physical activity questionnaire–short form for older adults in Vietnam.
        This questionnaire is publicly available, it is open access, and no permissions are required to use it. The IPAQ-SF includes four questions about physical activity in the previous 7 days regarding vigorous and moderate activity, walking and sedentary behaviors, and units in metabolic equivalents of task (METs)-minutes/week. Patients were considered compliant with moderate and high levels of physical activity according to the IPAQ-SF assessment guidelines.
      Additionally, anthropometric indicators were measured, including weight, height, waist circumference, and hip circumference.
      The investigators are 6th-year general medical students. They had completed a training program that oriented them both on the aims of the study and the specific instruments and methodologies employed.

      2.5 Data analysis

      Data were entered using Epidata 3.01 software and analyzed using Stata 14.0 and R software. Frequency and percentage were used to describe all variables.
      A Bayesian Model Averaging (BMA) approach was used to determine the association between “drug adherence” and “non-pharmacological adherence” (dependent variables) with other independent variables. The metrics used for the comparison of competing models were the Bayesian information criterion (BIC) and posterior probability (of a particular model being the correct model). The best model displayed the lowest BIC and highest posterior probability.

      2.6 Ethical consideration

      Participation in this study was voluntary. Written informed consent was obtained from all patients. Patients could withdraw from the study at any time without giving a reason.
      The study was approved by the Research Ethics Committee of the University of Medicine and Pharmacy at Ho Chi Minh City (Decision No. 373/HDDD-DHYD, dated June 2, 2020).

      3. Results

      3.1 Demographic, socioeconomic, and clinical characteristics of participants (Table 1)

      A total of 537 people aged ≥60 years with hypertension were enrolled. Of these, 63.7% were women. The majority of participants belonged to groups aged 60–70 (50.8%) and 71–80 (31.1%) years. More than 70% of the participants had a middle school diploma or above. Most of the participants were government employees (28.5%), merchants (22%), and housewives (22.3%), and most had health insurance (97%).
      Table 1Demographic, socioeconomic and clinical characteristics of participants (n = 537).
      FrequencyPercentage
      Gender
       Male19536.3
       Female34263.7
      Age group
       60–7027350.8
       71–8016731.1
       More than 809718.1
      Educational level
       No formal education112.1
       Elementary school11421.2
       Middle school12122.5
       High school16731.1
       College7413.8
       University or above509.3
      Past occupation
       Government employee15328.5
       Merchant11822.0
       Worker499.1
       Daily laborer9718.1
       Retired/Housewife12022.3
      Health insurance
       Yes52197.0
       No163.0
      Hypertension duration (n = 537)
       < 1 year264.8
       1–5 years15629.1
       5–10 years13525.1
       > 10 years22041.0
      Complications (n = 537)12322.9
      Comorbidities (n = 537)25246.9
      Diabetes (n = 537)7213.4
      Dyslipidemia (n = 537)12322.9
      Nutritional status (n = 535)
       Underweight285.2
       Normal16230.3
       Overweight11822.1
       Obese22742.4
      At-risk waist circumference
      Waist circumference is at risk when ≥90 cm in men or ≥80 cm in women.
      (n = 534)
      28553.4
      At-risk waist-hip ratio
      The waist/hip ratio is at risk when ≥0.90 in men or ≥0.85 in women.
      (n = 534)
      40976.6
      a Waist circumference is at risk when ≥90 cm in men or ≥80 cm in women.
      b The waist/hip ratio is at risk when ≥0.90 in men or ≥0.85 in women.
      Many of the patients had hypertension for >10 years (41%). The rate of complications from hypertension and other chronic diseases was 22.9% and 46.9%, respectively. Of the participants, 13.4% had diabetes mellitus and 22.9% had dyslipidemia.
      The proportion of patients with normal nutritional status was 30.3%, while the rate of overweight and obesity was 64.5%. Patients with an at-risk waist circumference and waist/hip ratio were 53.4% and 76.6%, respectively.

      3.2 Treatment adherence of patients (Fig. 1)

      The proportion of patients with drug compliance was only 11.7%.
      Among the non-pharmacological adjustments for managing hypertension, non-smoking and limiting alcohol were the most applied modifications, accounting for 93.5% and 92.2% of cases, respectively.
      The rate of having recommended follow-up visits was 76.9%, and the non-drug adherence behavior of salt intake reduction had the lowest rate (63.1%).

      3.3 Factors related to patient adherence

      3.3.1 Factors related to drug adherence

      The BMA process suggested ten models, among which the five best models for drug adherence are shown in Table 2. We chose the first model with the highest posterior probability (nearly 50%), which consisted of two variables: hypertension duration and comorbidities. In particular, the proportion of patients with drug compliance decreased by 0.66 times every five years of illness, and those with chronic comorbidities presented with 2.21 times the rate of drug compliance.
      Table 2Factors related to drug adherence of patients using BMA.
      ModelDrug adherenceOR (95% CI)p-valueBICPosterior probability
      1Hypertension duration0.66 (0.50–0.88)0.004– 2963.90.468
      Comorbidities2.21 (1.28–3.83)0.005
      Intercept0.29 (0.12–0.69)0.005
      2Comorbidities2.15 (1.25–3.70)0.006– 2961.80.161
      Intercept0.09 (0.06–0.13)<0.001
      3Hypertension duration0.67 (0.50–0.89)0.006– 2961.60.147
      Intercept0.42 (0.18–0.96)0.039
      4Intercept0.13 (0.10–0.17)<0.001– 2959.90.062
      5Hypertension duration0.66 (0.50–0.88)0.005– 2958.50.030
      Comorbidities2.25 (1.29–3.90)0.004
      Nutritional status1.15 (0.86–1.52)0.344
      Intercept0.19 (0.05–0.68)0.011

      3.3.2 Factors related to non-pharmacological adherence

      The BMA process suggested eleven models, among which the five best models for salt intake reduction are shown in Table 3. We chose the first model with the highest posterior probability (39.4%). This study found a statistically significant association between adherence to salt reduction and the presence of chronic comorbidities. People with chronic comorbidities had a compliance rate of only 0.52 times compared to those without comorbidities.
      Table 3Factors related to reduced salt intake of patients using BMA.
      ModelReduced salt intakeOR (95% CI)p-valueBICPosterior probability
      1Comorbidities0.52 (0.37–0.75)<0.001– 2650.80.394
      Intercept2.35 (1.83–3.03)<0.001
      2Dyslipidemia0.48 (0.32–0.72)<0.001– 2648.80.151
      Intercept2.04 (1.66–2.51)<0.001
      3Past occupation0.89 (0.80–0.99)0.041– 2648.40.118
      Comorbidities0.52 (0.36–0,74)<0.001
      Intercept3.30 (2.17–5.04)<0.001
      4Gender0.72 (0.50–1.03)0.075– 2647.60.082
      Comorbidities0.51 (0.36–0.73)<0.001
      Intercept2.70 (1.98–3.67)<0.001
      5Comorbidities0.65 (0.42–1.00)0.052– 2647.00.059
      Dyslipidemia0.64 (0.39–1.06)0.084
      Intercept2.35 (1.83–3.03)<0.001
      There was no statistically significant association between physical activity compliance and other characteristics in any of the models which the BMA process suggested (Supplement file, Table S1).
      The BMA process suggested 13 models, among which the five best models for follow-up compliance are shown in Table 4. We chose the first model with the highest posterior probability (36.2%). There was a statistically significant relationship between follow-up compliance and health insurance, diabetes, and obesity. The rate of follow-up compliance increased 5.67 times in patients with health insurance. Additionally, patients with diabetes or obesity adhered to follow-up visits 2.93 and 1.50 times, respectively, compared with those without these diseases.
      Table 4Factors related to follow-up compliance of patients using BMA.
      ModelFollow-up complianceOR (95% CI)p-valueBICPosterior probability
      1Health insurance5.67 (2.05–15.67)0.001– 2786.30.362
      Nutritional status1.50 (1.21–1.87)<0.001
      Diabetes2.93 (1.30–6.61)0.010
      Intercept0.17 (0.05–0.56)0.004
      2Health insurance6.33 (2.30–17.44)<0.001– 2784.70.166
      Nutritional status1.49 (1.20–1.85)<0.001
      Intercept0.18 (0.05–0.57)0.004
      3Educational level1.19 (0.99–1.44)0.062– 2784.20.130
      Health insurance5.98 (2.20–16.23)<0.001
      Nutritional status1.48 (1.20–1.84)<0.001
      Diabetes3.11 (1.36–7.14)0.007
      Intercept0.09 (0.02–0.35)<0.001
      4Health insurance5.30 (1.95–14.40)0.001– 2782.40.053
      Nutritional status1.51 (1.21–1.87)<0.001
      Diabetes3.04 (1.34–6.88)0.008
      Dyslipidemia1.51 (0.88–2.58)0.137
      Intercept0.17 (0.05–0.53)0.002
      5Gender1.40 (0.90–2.19)0.137– 2782.30.049
      Health insurance5.54 (1.96–15.65)0.001
      Nutritional status1.50 (1.21–1.86)<0.001
      Diabetes2.94 (1.30–6.66)0.010
      Intercept0.16 (0.05–0.52)0.003

      4. Discussion

      4.1 Demographic, socioeconomic, and clinical characteristics of participants

      The duration of hypertension in study participants was mostly over ten years (41%). This result is much higher than that reported by Tran Thi My Hanh in some communes in Thai Binh, Hung Yen (2.6%).
      • Hanh Tran Thi My
      Evaluation of Intervention Results to Improve Blood Pressure Monitoring Practice and Treatment Adherence in Hypertensive People over 50 Years Old in Tien Hai district, Thai Binh Province, Ph.D of Public Health.
      This difference may be due to the different study times and locations: one was in the countryside, and one was in the city. Furthermore, the difference may be owing to the sampling method used in the Hung Yen study where the author used a list of patients visiting the clinic to increase the chances of meeting eligible patients to enroll in the study, which could have led to a lower percentage in group ten years duration of hypertension.
      The proportion of patients with hypertension complications accounted for approximately 23%. Moreover, the percentage of people in the study with chronic comorbidities was high (47%). We found that this rate was different in other studies. In a study conducted at Trung Vuong Hospital, the proportion of patients with diabetes and kidney failure was 26.7% and 7.7%, respectively, which was lower than the rates in our study.
      • My Hanh Nguyen Thi
      • Duyen Nguyen Thi My
      • Khanh Ly Huy
      • et al.
      Investigation of the relationship between medication adherence and blood pressure control in hypertensive patients on outpatient treatment.
      However, a study at Vinh City General Hospital revealed a much higher rate (73.7%) of patients diagnosed with other diseases,
      • Thu Hang Nguyen
      • Nguyen Thi Thuy Duong
      • Ho Thi Dung
      • Thuy Nguyen Thi Minh
      Survey on hypertensive outpatients pharmacologic medication compliance at Vinh City General Hospital in 2018.
      perhaps because only diabetes and kidney failure were investigated, while studies that investigated general diseases, such as COPD, asthma, dyslipidemia, overweight, obesity, diabetes, and kidney failure, had higher rates of comorbidities.
      The proportion of patients with normal nutritional status was approximately 30%, while those with overweight and obesity accounted for 64.5%. Additionally, other risk indicators, such as waist circumference and waist-hip ratio, were high among the participants at 53.4% and 76.6%, respectively. These rates were higher than those in the previous study in District 10 by Vo Thi Xuan Hanh where the rates of overweight/obesity, at-risk waistline, and at-risk waist/hip ratio were 47.5%, 31,9%, and 52.1%, respectively.
      • Hanh Vo Thi Xuan
      • Cao Nguyen Hoai Thuong
      • Phan Thi Kim Hoang
      • et al.
      The prevalence of hypertension and diabetes through a survey on a representative sample in the inner-city district of Ho Chi Minh City.
      The difference may be because our study evaluated people with hypertension aged ≥60 years, whereas Vo Thi Xuan Hanh evaluated people aged ≥18 years. However, compared to a similar study in elderly patients with hypertension in Ukraine, the obesity rate (25.4%) was also lower than that in our study
      • Nalotova E.N.
      • Alesinskiy M.M.
      • Berezin A.E.
      • Nalotov S.V.
      Adherence to Antihypertensive Medication in the older hypertensive patients: the role of blood pressure measurement assistance.
      ; this could be owing to different countries using different criteria for determining overweight and obesity.

      4.2 Patient treatment adherence

      4.2.1 Drug adherence

      The proportion of patients who complied with the Morisky-8 scale in this study was less than that in other studies, although the pharmacology adherence rates in these studies varied. In studies in Vietnam, this ratio ranged from 26.3%
      • The Xuyen Pham
      Status of Hypertension in People 45-64 Years Old in Dien Bien District, Dien Bien Province and Cost-Effectiveness of Interventions.
      to 28.4%
      • Hanh Tran Thi My
      Evaluation of Intervention Results to Improve Blood Pressure Monitoring Practice and Treatment Adherence in Hypertensive People over 50 Years Old in Tien Hai district, Thai Binh Province, Ph.D of Public Health.
      to 87.5%.
      • Thu Hang Nguyen
      • Nguyen Thi Thuy Duong
      • Ho Thi Dung
      • Thuy Nguyen Thi Minh
      Survey on hypertensive outpatients pharmacologic medication compliance at Vinh City General Hospital in 2018.
      The compliance rate in the studies conducted in the community was low compared to that of studies conducted in hospitals. This difference may be because of a greater disease awareness among patients at the hospital. Pharmacology compliance rates in other countries also varied. A study in 2019 in sub-Saharan African countries revealed compliance rates ranging from 15% to 55%,
      • Terline D.M.
      • Kane A.
      • Kramoh K.E.
      • et al.
      Factors associated with poor adherence to medication among hypertensive patients in twelve low and middle income Sub-Saharan countries.
      while in Saudi Arabia
      • Algabbani F.M.
      • Algabbani A.M.
      Treatment adherence among patients with hypertension: findings from a cross- sectional study.
      and Ukraine
      • Nalotova E.N.
      • Alesinskiy M.M.
      • Berezin A.E.
      • Nalotov S.V.
      Adherence to Antihypertensive Medication in the older hypertensive patients: the role of blood pressure measurement assistance.
      rates were 42.2% and 51.8%, respectively. According to a meta-analysis of drug adherence rates in hypertensive patients aged ≥60 years using the MMAS-8 scale, this rate ranged from 18.2% to 90.4%, with an average of 68.8%.
      • Uchmanowicz B.
      • Jankowska E.A.
      • Uchmanowicz I.
      • Morisky D.E.
      Self-reported medication adherence measured with Morisky medication adherence scales and its determinants in hypertensive patients aged ≥60 Years: a systematic review and meta-analysis.
      The reason for the relatively low compliance in our study was because a large proportion of patients missed taking their medication or quit taking medication when they felt that their BP was stable. Additionally, a few patients purchased medication using other patients’ prescriptions or previous prescriptions, without follow-up or consultation with a physician.

      4.2.2 Non-pharmacological adherence

      Among the non-pharmacological compliance assessments using the MOH recommendations, we found that compliance with smoking cessation and alcohol consumption restriction were the highest, possibly owing to the high rate of female participants in our study. A study at Vinh General Hospital also reported a similar rate of smoking cessation, but the rate of participants who applied alcohol restriction was less than that in our study.
      • Thu Hang Nguyen
      • Nguyen Thi Thuy Duong
      • Ho Thi Dung
      • Thuy Nguyen Thi Minh
      Survey on hypertensive outpatients pharmacologic medication compliance at Vinh City General Hospital in 2018.
      However, according to a Ukraine study, the percentage of smokers was 26.3%,
      • Nalotova E.N.
      • Alesinskiy M.M.
      • Berezin A.E.
      • Nalotov S.V.
      Adherence to Antihypertensive Medication in the older hypertensive patients: the role of blood pressure measurement assistance.
      which was higher than that in our study. These differences may be because of the high proportion of men in this study. According to research at Quang Ninh General Hospital, only half the participants adhered to these two behaviors.
      • Thi Thom Nguyen
      • Bui Van Cuong
      • Hanh Nguyen Hong
      • Huong Pham Thi Thu
      • Sinh Do Minh
      The status of hypertension treatment compliance of outpatients at Quang Ninh General Hospital in 2017.
      This difference may stem from the age and gender characteristics of the study participants. Most of the patients in our study and Nguyen Thu Hang's study were elderly female patients, while the Quang Ninh province study contained a higher proportion of men aged 45 years.
      A total of 76.9% of patients had regular follow-up visits, which was higher than the 60.4% reported by Quang Ninh.
      • Thi Thom Nguyen
      • Bui Van Cuong
      • Hanh Nguyen Hong
      • Huong Pham Thi Thu
      • Sinh Do Minh
      The status of hypertension treatment compliance of outpatients at Quang Ninh General Hospital in 2017.
      This can be explained by the presence of many medical facilities and highly qualified medical staff in District 10 to help patients access medical services and obtain advice on the benefits of timely medical follow-up. Moreover, research is conducted on the elderly. Because most elderly patients are retired, it is easier to schedule follow-up visits. However, this level of compliance needs to be maintained and further improved through communication and patient mobilization to prevent hypertension complications.
      The proportion of people with moderate and high physical activity was high (64.3%). Until now, physical activity in hypertension studies was not evaluated, or was assessed by the patient's participation in exercise ≥30 min/day and ≥5 times/week. Therefore, accurate results of the patients' physical activity were not provided. Moreover, it would be difficult to make comparisons between studies when disagreeing on the evaluation method. To evaluate physical activity in this study, we used the IPAQ-SF scale, a proven and reliable tool for measuring and monitoring the physical activities of elderly patients in Vietnam.
      • Tran D.V.
      • Andy H.L.
      • Thuy B.A.
      • Nguyen C.T.
      • Hoang D.V.
      Reliability and validity of the international physical activity questionnaire–short form for older adults in Vietnam.
      The scale included only four questions and was easy to implement and suitable for community surveys. The results will form the basis for future comparisons between studies and intervention programs to enhance physical activity in elderly patients with hypertension.
      Among all non-pharmacological adherence behaviors, reducing salt intake had the lowest compliance rate (63.1%). This rate was higher than that reported by Nguyen Thi Thom (54.8%)
      • Thi Thom Nguyen
      • Bui Van Cuong
      • Hanh Nguyen Hong
      • Huong Pham Thi Thu
      • Sinh Do Minh
      The status of hypertension treatment compliance of outpatients at Quang Ninh General Hospital in 2017.
      but lower than that reported by Nguyen Thu Hang (70%).
      • Thu Hang Nguyen
      • Nguyen Thi Thuy Duong
      • Ho Thi Dung
      • Thuy Nguyen Thi Minh
      Survey on hypertensive outpatients pharmacologic medication compliance at Vinh City General Hospital in 2018.
      The special feature of our study is that daily salt consumption was assessed through the FFQ questionnaire, while in these studies it was only evaluated through patient interviews. By assessing patient food consumption frequency, we calculated the average amount of sodium consumed each day by the patient. Therefore, this result was more accurate in reflecting the patient's salt reduction compliance. According to the 2015 national survey on the risk factors for non-communicable diseases in Vietnam, over 90% of Vietnamese people regularly consumed too much salt; the average salt consumption of Vietnamese adults was 9.4 g/day (10.5 g for men and 8.3 g for women), which is two times higher than the WHO's recommendation of less than 5 g/person/day.
      • Department of Preventive Medicine
      Announcement of Results of National Survey of Risk Factors for Non-communicable Diseases in 2015.
      However, although research has shown that 90% of Vietnamese people regularly eat excess salt, only 69.3% of participants believed that they consumed the recommended amount of salt, and only 16.1% (19.7% men and 12.4% women) believed they consumed more salt than recommended. These findings should be considered when conducting an intervention in this group because it is necessary to help the patients realize their excessive daily salt intake and ways to reduce it.

      4.3 Factors related to patient adherence

      4.3.1 Factors related to drug adherence

      We included the BMA analysis to determine the factors that influence drug compliance to make recommendations for intervening.
      According to our results, individuals with a longer hypertension duration were more likely to be less adherent to medication, and participants with chronic comorbidities had a compliance rate 2.21 times those without other chronic diseases. It can be reasoned that the longer the patients had the disease, the more neglectful they were to not take medication or voluntarily stop medication when they felt that their BP had stabilized. Prolonged treatment also affected the patients psychologically and they did not maintain compliance at the time of diagnosis. Because patients with additional comorbidities require other medications, this may help maintain medication compliance. Moreover, anxiety and fear of disease risks from not taking medication may increase patient compliance.
      When compared with other studies in Vietnam, our study results coincided with those of the study by Nguyen Thi My Hanh on associated diabetes, but the time factor of treating hypertension was different.
      • My Hanh Nguyen Thi
      • Duyen Nguyen Thi My
      • Khanh Ly Huy
      • et al.
      Investigation of the relationship between medication adherence and blood pressure control in hypertensive patients on outpatient treatment.
      My Hanh's study showed age as a factor, which may be because subjects aged ≥18 years were evaluated. Young patients may have different compliance behaviors than the elderly, thereby leading to discrepancies in results. According to a Hanoi study conducted by Vu Xuan Phu, after incorporating variables into the multivariate model, only gender and knowledge of hypertension were the variables related to treatment adherence.
      • Phu Vu Xuan
      • et al.
      Study on some factors related to hypertension treatment adherence in 25-60 year old patients in 4 wards of Hanoi city.
      Although this study controlled for confounding factors, it is reasonable for the subjects to have different ages than those of ours.

      4.3.2 Factors related to non-pharmacological adherence

      Our research identified factors that were related to the variables of patient non-drug adherence by using BMA. In previous studies, authors mainly focused on identifying factors related to drug adherence but did not consider factors affecting patients’ recommended behaviors.
      In this study, the results showed that for salt reduction compliance, people with chronic comorbidities had poorer adherence rates than those without other chronic diseases. This may be due to behaviors that do not reduce daily salt intake as recommended, which can lead to other chronic diseases. Moreover, our study only measured salt consumption through high-salt foods; hence, the percentage of patients who adhered to salt reduction may actually be higher than the reality. The rate of salt reduction adherence in hypertensive patients has also been reported worldwide, ranging from 57% to 80%.
      • Buda E.S.
      • Hanfore L.K.
      • Fite R.O.
      • Buda A.S.
      Lifestyle modification practice and associated factors among diagnosed hypertensive patients in selected hospitals, South Ethiopia.
      Having comorbidities is considered one of the factors that reduces the patient's adherence to lifestyle modification. Thus, salt reduction has not been given much attention in elderly patients with hypertension, which is likely to increase the risk of complications as well as other chronic diseases. Conversely, in patients with multiple comorbidities, salt reduction adherence may be more difficult to achieve. Therefore, clinicians should pay more attention to salt consumption when implementing treatment guidelines in these patients.
      Our study also found an association between higher follow-up compliance and having health insurance, diabetes, or obesity. This is because health insurance will pay for a doctor's consultation, diagnostic tests, medicine cost, and hospitalization expenses; therefore, the patient may return to the hospital more frequently and have regular check-ups. Moreover, when there are several comorbidities, the patient will need close monitoring and periodic tests; thus, a higher compliance rate is influenced. Frequent follow-up visits help doctors assess treatment effectiveness, detect adverse drug reactions, or detect early complications.
      • Whelton P.K.
      • Carey R.M.
      • Aronow W.S.
      • et al.
      ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults.
      However, in Vietnam, the cost of hypertension examination and treatment is still a burden. In a recent study, the total cost of one treatment for hypertension was 199,019 VND.
      • Chung Nguyen Thanh
      • Ha Ta Ngoc
      • Le Van Hieu
      Analysis of the cost of treatment for hypertension at the grassroots health level in Ha Nam province in 2019 and some related factors.
      Although not too expensive, hypertension is a disease that requires lifelong treatment, plus monthly follow-up visits or other costs, making the total cost incalculable. Therefore, health insurance is considered a solution to help patients not only financially, but also to better adhere to treatment to achieve high efficiency.
      Non-adherence to medication is prevalent in patients with hypertension. Therefore, interventions to improve adherence in both pharmacological and non-pharmacological treatments are necessary. A program which includes continuous monitoring of regular medication use, salt intake reduction, physical activity enhancement, weight loss, ideal weight maintenance, and regular follow-up visit attendance is needed. In particular, the intervention program should pay attention to patients who do not have health insurance and those with additional long-term illnesses.

      Funding

      This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

      Declaration of competing interest

      None.

      Acknowledgements

      The authors declare that there is no competing interest.
      The authors thank all study participants and all data collectors, for this study would not have been possible without them. They also thank the District 10 Health Center for supporting the data collection process.

      Appendix A. Supplementary data

      The following is the Supplementary data to this article:

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