Lower BP targets warranting initiation of therapy are recommended in patients with existing CVD, as well as in those without CVD but who have a high risk of CVD, diabetes, or chronic kidney disease, and an SBP of 130–139mmHg.¹

Any of the following three classes of drug classes are recommended as initial treatment:¹

1. Thiazide and thiazide-like agents
2. Angiotensin-converting enzyme inhibitors (ACEis)/angiotensin-receptor blockers (ARBs)
3. Long-acting dihydropyridine calcium channel blockers (CCBs).

Hypertension treatment algorithms

The WHO developed two algorithms for the effective pharmacological treatment of hypertension combined with lifestyle changes. Both algorithms recommend rechecking BP every four to six weeks. If BP is a goal, follow-up can be scheduled every three to six months.¹

Algorithm one (combination therapy) recommends:¹ 

1. Start with an ARB/CCB combination at half-maximal doses (eg telmisartan 40mg/amlodipine 5mg) once a day.
2. If BP is not at goal, increase ARB/CCB (double the dose to telmisartan 80mg/amlodipine 10mg once a day).
3. If BP is not at goal, add a thiazide/thiazide-like diuretic at half-maximal dose (hydrochlorothiazide [HCTZ] 25mg or chlorthalidone 12.5mg once a day).
4. If BP is not at goal, increase the thiazide/thiazide-like diuretic (double the dose to HCTZ 50mg or chlorthalidone 25mg once a day).
5. If BP goal is still not reached, refer patient to a specialist.

Algorithm two (monotherapy) recommends:¹

1. Start with a CCB at half-maximal dose (amlodipine 5mg) once a day.
2. If BP is not at goal, increase ARB/CCB (double the dose to telmisartan 80mg/amlodipine 10mg once a day).
3. If BP is not at goal, add a thiazide/thiazide-like diuretic at half-maximal dose (HCTZ 25mg or chlorthalidone 12.5mg once a day).
4. If BP is not at goal, increase the thiazide/thiazide-like diuretic (double the dose to HCTZ 50mg or chlorthalidone 25mg once a day).
5. If BP is not at goal, refer to a specialist.

Non-pharmacological interventions

The primary goal of treating patients living with hypertension is to reduce mortality and the risk of CV and other complications. Apart from pharmacological interventions, lifestyle changes are a well-established way for lowering BP.³

Non-pharmacological approaches to treatment or prevention of hypertension include:¹

• Reducing salt intake (to less than 5g daily)
• Eating more fruit and vegetables
• Being physically active on a regular basis
• Avoiding use of tobacco
• Reducing alcohol consumption
• Limiting the intake of foods high in saturated fats
• Eliminating/reducing trans fats in diet.

Salt comprises 40% sodium and 60% chloride. Salt is the major source of sodium in the diet. According to Feng et al, the current salt intake averages about 10g/day in most countries. Because the human body has not adapted to excrete large amounts of salt, the repercussions on our health are multiple. Excessive salt intake can cause key target organ damage.⁴

It is well known that hypertension is a major cause for CVD. Numerous studies have shown that reducing salt intake lowers BP, thus reducing the risk of CVD. Excessive salt intake has also been linked to chronic kidney disease progression, stomach cancer, renal stones, osteoporosis, brain disease and disorders (eg cognitive impairment and Alzheimer disease).⁴

One of the largest studies on the effects of salt on BP, was the International Study of Sodium, Potassium, and Blood Pressure (INTERSALT) study (n=10 079 adults from 32 countries), which demonstrated a direct association between salt intake and an increase in BP – especially in older and Black patients.⁴

A dose-response relationship between salt intake and BP has also been demonstrated. Two controlled trials where participants were assigned different levels of salt intake: 11.2g/day, 6.4/day, and 2.9g/day in one, and 8g/day, 6,4g/day in the other, demonstrated that BP changes with salt intake, so that the lower the salt intake, the lower the BP.⁴

These findings suggest that while reducing salt to the recommended intake of 5g/day will bring health gains, a further reduction to 3g/day will be more beneficial.⁴

How does salt affect the body?

Increased salt consumption may provoke water retention, thus leading to a condition of high flow in arterial vessels. The mechanism of pressure natriuresis has been proposed as a physiologic phenomenon where an increase in BP in the renal arteries causes increased salt and water excretion. This haemodynamic load, as studies with animal models have shown, may lead to adverse microvascular remodelling by the effects of increased BP levels.⁴

High sodium intake and increased BP levels are linked to changes in vascular resistances, but the mechanisms controlling this phenomenon may not be only viewed as a reflex pressor response aimed at increasing sodium excretion.⁴

Excessive salt intake may lead to microvascular endothelial inflammation, anatomic remodelling, and functional abnormalities, even in non-hypertensive patients.  Studies have also shown that changes in sodium plasma levels do not only exert their effects on small resistance arteries but may also affect the function and structure of large elastic arteries.⁴

How effective are salt reduction strategies?

In Finland in the late 1970s, a salt-reduction program combining salt-awareness campaigns, collaboration with the food industry, and

adoption of salt-labelling legislation, resulted in a salt reduction from ~14g/day in 1972 to ~9g/day in 2002, leading to a 10mmHg decrease in both SBP and DBP and a 75% to 80% reduction in CVD mortality, despite increases in obesity and alcohol consumption during that time.⁴

The United Kingdom’s salt-reduction programme, by setting voluntary, incrementally lower salt reduction targets for >85 food categories, led to a 15% reduction in salt intake (from 9.5g/day in 2003 to 8.1g/day in 2011. This caused a 2.7mmHg fall in population SBP and a significant reduction in mortality from stroke and ischaemic heart disease.⁴

Since the creation of the Dietary Approaches to Stop Hypertension Sodium (DASH) more than 25 years ago, numerous trials have demonstrated that it consistently lowers BP in different subgroups of patients with hypertension and prehypertension.⁵

As a result, the diet is now recommended by most international guidelines as part of hypertension prevention strategies. The original DASH trial conducted in 1997, demonstrates that a combination of lower salt intake (2.3g/day of sodium or 5.8g/day of sodium chloride) combined with the DAHS diet effectively lower BP levels.^4,6

The DASH diet recommends increased consumption of fruits, vegetables, low-fat dairy, whole grains, poultry, fish, and nuts while limiting the intake of red meat and added sugars.⁵

It is relatively low in total fat (27%–28% of total calories), saturated fat (~6% of total calories), and sodium (2.3g/day). There is substantial evidence that the DASH diet consistently reduces BP (–5.5mmHg/–3.0mmHg as early as two weeks after baseline). DASH was particularly effective for those with hypertension (SBP and DBP change: −10.7mmHg and −4.7mmHg, respectively) and among Black individuals (SBP and DBP change: −6.8mmHg and −3.7mmHg, respectively).⁷

In context, a DASH diet can also provide further CV benefits. In the DASH-Sodium Trial, adults with elevated BP (n=412) were randomised to either a typical American diet or the standard DASH diet.⁷

Within their assigned diet group, participants consumed foods to achieve a high, moderate, or low sodium intake for 30-day periods in a randomised crossover design (approximately 3.4g/day, 2.3g/day, and 11.5g/day per 2100 kcal, respectively). Sodium reduction dose-dependently lowered SBP and DBP across all subgroups (eg sex, ethnicity, and hypertensive status) with both the control diet and the DASH diet. Effects were greater in participants who were older and who had hypertension.⁷

Compared to the control diet, the DASH diet produced significantly lower systolic BP at each sodium level, and the combination of the two interventions - sodium restriction and the DASH diet - provided the greatest benefit.⁷

A systematic review of six studies concluded that a DASH-style diet significantly reduced the risk of CVD, coronary heart disease, stroke, and heart failure incidence by 20%, 21%, 19%, and 29%, respectively.⁷

Conclusions

Despite the fact that an estimated 400 000 CVD events could be prevented over 10 years following DASH recommendations, adherence is poor, write Steinberg et al.⁵

Numerous factors play a role, the biggest being the food environment. Energy-dense, nutrient-deficient foods are highly accessible (fast food outlets) and inexpensive, while fruits and vegetables tend to be more expensive.⁵

Steinberg et al propose the following to improve adherence:⁵

• Primary care clinicians have an opportunity to provide counselling about dietary behaviours for hypertension management. However, clinicians report that limited time, knowledge, and perceived efficacy are barriers to dietary counselling. Refer patients to registered dietitians familiar with DASH
• Making patients aware that DASH can be adopted at low cost and among low-income individuals. Foods such as dried beans or frozen vegetables are inexpensive and DASH accordant
• Innovative strategies to induce sustainable behaviour change on an individual level. Most adults own mobile or smartphone which poses an opportunity to reach high-risk patients. An emerging strategy to improve patient self-management is the use of digital health tools (eg apps).

REFERENCES:

1. WHO (2021). Guideline for the pharmacological treatment of hypertension in adults. file:///C:/Users/rene.bosman/Downloads/9789240033986-eng.pdf
2. Masilela C, et al. ross-sectional study of prevalence and determinants of uncontrolled hypertension among South African adult residents of Mkhondo municipality. BMC Public Health, 2020.
3. Paczkowska-Walendowska M, et al. Single-Pill Combination to Improve Hypertension Treatment: Pharmaceutical Industry Development. International Journal of Environmental Research and Public Health, 2022.
4. Feng JH, Tan M, Ma Y, MacGregor GA. Salt Reduction to Prevent Hypertension and Cardiovascular Disease. JACC State-of-the-Art Review. Journal of the American College of Cardiology, 2020.
5. Steinberg D, Bennett GG and Svetkey L. The DASH Diet, 20 Years Later. JAMA, 2017.
6. Sachs FM, Svetkey LP, Volmer WM, et al. Effects On Blood Pressure Of Reduced Dietary Sodium And The Dietary Approaches To Stop Hypertension (Dash) Diet. NEJM, 2001.
7. Richter C, Skulas-Ray A, Kris-Etherton P. Chapter 27 - Nutrition in the Prevention and Treatment of Disease (Fourth Edition), 2017.