2.1 Hypertension .1 Epidemiology
2.1.8. Factors influencing blood pressure control
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4.6%, retinopathy in 2.2%, ischaemic heart disease in 1.7% and peripheral vascular disease in 3.6% of patients.80 The study population were adults aged 18-64 years living in a rural community. The association between increasing age and target organ damage was not elucidated in the study, however, target organ damage was significantly higher in those with severe hypertension and diabetes mellitus.80 Ayodele et al. also studied pattern of target organ damage among adults with treated hypertension in an outpatient clinic in South-western Nigeria and found left ventricular hypertrophy in 31%, heart failure in 10.8%, chronic kidney disease in 18.2% and stroke in 8.9% of the patients.81
In South-east Nigeria, hypertension with its complications accounted for 69.6% of the cardiovascular system in-patient admissions, with congestive cardiac failure in 26.5% of cases.
The case fatality rate of hypertension with its related complications was 42.9% in the study.82 The high figures recorded in this study could be because the patients requiring admission would have had cardiac-related emergencies, and were not healthy subjects as would have been seen in out-patient clinic or within the community.
Apart from the above hypertension-related complications in Nigerians, risk factor from coronary artery disease was as high as 53% of cases and hypertensive retinopathy was responsible for 4.6% to 13% of retinal disease over the past five decades (1970-2011) in a review study in Nigeria.36
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hypertension causes prolonged ill health and imposes serious morbidity and mortality risks.
Suboptimal adherence with therapy has been found to be the most important reason for this.84
48 Health-care related factors
Poor access to health care: Availability of health care within easy reach of the people with basic technologies to manage people with hypertension will help with its control. The health care services should incorporate combination of interventions for early detection, self-monitoring of blood pressure with digital measurement devices which are affordable.33 However, developing and resource limited countries have poor access to health care delivery in terms of number of clinics or hospitals and available infractructure, hampering early diagnosis and treatment interventions.61
Medication problems: The availability and appropriate use of essential medicines to prevent complications in people with moderate to high cardiovascular risk. However in resource limited countries like Nigeria, generic drugs may not be affordable by majority. The rate of counterfeit drugs is also high in such communities.33 Furthermore, the cost of medications in developing countries also has a significant contribution to blood pressure control. Patients with hypertension spend considerable amount on medications which becomes unbearable for maintenance even when complications sets in. In a study conducted at Igbo-ora (semi-rural community) in South-western Nigeria, it was reported that about half of the patients with hypertension were spending a tenth or more of their income on their health care related expenses.85 The cost of medications and the pill burden (number of medications to be taken) are known important factors influencing patients adherence to medical interventions.84
Health provider therapeutic inertia: This is the failure by providers to increase therapy in the setting of identified poor blood pressure control in accordance to available treatment guidelines.
The health care providers’ poor knowledge of available treatment guidelines and low usage for
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those who are aware of the guidelines for optimal dosage regimen of medications, is becoming a well-recognized barrier to achieving improved control rates.68
Political will: This is needed to foster evidenced-based policy interventions that are cost effective for the country. These will be targeted at the risk factors and improvement in health care delivery. Collaborative efforts of the government and food agencies can occur in activities such as: ban on importation, sale advertising and promotion of tobacco and alcoholic beaverages, salt reduction through mass-media campaigns and reduced salt content in processed foods, replacement of trans-fats with polyunsaturated fats, public awareness programme about diet and physical activity.33 The government should also make special effort to supply basic drugs for hypertension treatment at the primary health care levels at affordable prices for the masses in resource limited communities.
Patient-related factors
Lifestyle modification adherence: Practise of therapeutic lifestyle modifications involving weight reduction, exercising, healthy diet, alcohol reduction and smoking cessation has been found to be difficult. Patients’ adherence, especially to therapeutic lifestyle measures and behavioural modification recommendations is notoriously difficult to achieve, but essential to the success of managing chronic diseases including hypertension. Patients can find lifestyle behaviours (for example diet, weight reduction and physical activity) hard to change and maintain for a long period. Svetkey et al. in a randomized controlled trial on weight maintenance intervention on 1032 overweight or obese adults who had hypertension, dyslipidaemia or both, and had lost 4 kg weight over 6 months had problem of weight maintenance.86 Respondents in the two randomized groups (self-directed control or interactive technology based interaction) regained weight after a 30 months follow-up period. They found that strict adherence to lifestyle
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changes and the extent to which recommendations are followed present difficult and complex challenges to patient.86
Medication adherence: It is generally defined as the extent to which a patient’s behaviour, with respect to taking medication, corresponds with agreed recommendations from a healthcare provider.87 In literature, the term adherence is interchangeably used with compliance. However, adherence is preferred because adherence requires the patient’s agreement to the recommendations rather than patient’s passively following the doctor's orders as in compliance.87 Adherence with treatment can be influenced by socio-demographics like age, level of education; financial constraints, healthcare utilization, forgetfulness, medication pill burden and side effects, and especially lack of effective social support networks.84 _ENREF_47 Steiner et al. found a weak association while attempting to classify individuals with respect to adherence of antihypertensive medication using socio-demographic and clinical characteristics.88 Other factors limiting adherence in older adults include declining cognitive process, vision, hearing, health literacy and social and financial resources. Older adults therefore require careful supervision of all of their medications in order to improve adherence.
Level of medication adherence can be assessed by several methods such as pill count, electronic monitoring (MEMS), pharmacy records and prescription claims, and patients’ self-report interview.87 Self-reported adherence is a less sensitive measure of non-adherence when compared with objective measures like MEMS or pill count. However, it is clinically relevant to blood pressure control, hence a valid tool for research adherence measurement.89
The reasons for non-adherence are often multifactorial and influenced by multiple barriers.
Although in the WHO multidimensional adherence model adherence barriers are organized into five categories namely socioeconomic factors, factors associated with the health care team and
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system in place, disease-related factors, therapy-related factors, and patient-related factors; they can also be categorized into patient-specific (e.g. forgetfulness, beliefs), medication-specific (e.g.
complexity of medication), logistic (e.g. frequency of clinic visits and pharmacy fills), and disease-specific (e.g. absence of symptoms for hypertension) barriers.89
Despite the benefits derived from adherence to drug therapy and practice of lifestyle modification in patients with hypertension, poor adherence has been found to be common in clinical practice leading to inadequate blood pressure control. Krousel-Wood et al. in the Cohort Study of Medication Adherence in Older Adults (CoSMO) Los Angeles, USA, found low adherence in 14.1% of older adults with hypertension.89 Contrast to this, in South-east Nigeria, Okwuonu found low adherence in 68.7% of patients on antihypertensive medications.68 The latter study involved all adults and the participants had more varied reasons for non-adherence not specific to elderly age group.
Reduction of co-morbid risk factors: Obesity and weight gain are major risk factors for hypertension and are also determinants of the rise in blood pressure that is commonly observed with aging. It exacerbates other chronic diseases like hypertension, diabetes, osteoarthritis, gallstones and dyslipidaemia.90 The control of these factors therefore is pertinent for control of blood pressure.