Non-pharmacological factors for hypertension management: a systematic review of international guidelines

Abstract

Lifestyle modifications are one of the cornerstones of hypertension prevention and treatment. We aimed to systematically review hypertension guidelines on their recommendations on non-pharmacological factors including lifestyle interventions, to highlight strength of evidence, similarities, and differences. This systematic review was registered with the international Prospective Register of Systematic Reviews (CRD42021288815). Publications in MEDLINE and EMBASE databases over 10 years since January 2010 to June 2020 were identified. We also included the search from websites of organizations responsible for guidelines development. Two reviewers screened the titles and abstracts to identify relevant guidelines. Two reviewers independently assessed rigour of guideline development using the AGREE II instrument, and one reviewer extracted recommendations. Of the identified guidelines, 10 showed good rigour of development (AGREE II ≥ 60%) and were included in the systematic review. The guidelines were consistent in most recommendations (reduced salt intake, weight, dietary patterns, increased physical activity and smoking cessation, and limiting alcohol intake). Some areas of disagreement were identified, regarding recommendations on novel psychological and environmental factors such as stress or air pollution, alcohol intake thresholds, meat, coffee and tea consumption and refined sugars. Current guidelines agree on the importance of lifestyle in the treatment and prevention of hypertension. Consensus on smoking cessation, limited salt intake, increased physical activity support their integration in management of hypertensive patients and in public health measurements in general population as preventative measurements. Further research into the role of environmental and psychological factors may help clarify future recommendations.

See the editorial comment for this article ‘Lifestyle recommendations as treatment for arterial hypertension: a time to review’, by H. Hanssen, https://doi.org/10.1093/eurjpc/zwac202.

Introduction

Hypertension is the most prevalent noncommunicable chronic disease and cardiovascular risk factor and affects a large proportion of the general population. In 2010, 31% of the global adult population had a diagnosis of hypertension.¹ As its prevalence is estimated to further increase over the next 10 years, the World Health Organization (WHO) has prioritized a reduction to 25% by 2025 as one of its global targets.²

All the major scientific societies’ hypertension guidelines include lifestyle modifications as fundamental part of treatment at any stage of hypertension, including those at highest risk with resistant hypertension.^3–5 Integration and adherence to long-term comprehensive lifestyle interventions (such as smoking cessation, salt reduction, dietary and psychological interventions, and increased physical activity) leads to lower blood pressure (BP) and improved cardiovascular biomarkers^6,7 and to reduced medication load.⁸

Therefore, recommendations for non-pharmacological interventions are an essential part of treatment and prevention of hypertension now more than ever, with more emphasis given to the strength of evidence in their support when included in guidelines. However, it is unclear whether guidelines are consistent in their recommendations.

Furthermore, due to the evidence from the SPRINT trial⁹ but also other studies and meta-analyses,^10,11 some international guidelines have recommended a lower threshold for the diagnosis of hypertension.⁵ Consequently, a much larger population of patients with lower cardiovascular risk profile will be recommended to implement lifestyle modifications to reduce their BP, while initiation of pharmacological treatment, in conjunction with lifestyle advice, will be reserved for those with a 10-year cardiovascular risk higher than 10% (such as in presence of diabetes and/or renal disease).^5,12

Lifestyle changes in hypertension include several non-pharmacological interventions and factors with different levels of evidence and strength of recommendation. Moreover, they can differ among societies and group of patients.

We aimed to systematically review contemporary hypertension guidelines from different scientific societies and the selection of appropriate non-pharmacological interventions based on currently available evidence, highlighting similarities and differences and strength of recommendations. By a critical appraisal, we sought to provide a summary to help healthcare professionals and researchers involved in hypertension treatment and prevention and provide highlight potential gaps for future research or guideline development.

Methods

Data sources and guideline selection

We conducted an updated systematic review of guidelines for primary (essential) and/or resistant arterial hypertension. The systematic review was registered with the international Prospective Register of Systematic Reviews (CRD42021288815). The search strategy is reported in Supplementary material online, Table S1 . Practice Guidelines, guidelines guidance, and scientific societies position papers and statements were included. References that met the Institute of Medicine's definition of a guideline were included (i.e. ‘statements that include recommendations, intended to optimize patient care, that are informed by a systematic review of evidence and an assessment of the benefits and harms of alternative care options).¹³ Abstracts, conference and opinion papers, case studies and letters, commentaries, editorials, and papers lacking full text were excluded. Guidelines focused on pre-eclampsia and secondary hypertension were also excluded.

Our search was restricted to national and international guidelines written in English.

We searched for published guidelines using MEDLINE and EMBASE between January 2010 and June 2020. We also searched websites of guideline development organizations, including those affiliated with all the guidelines included in our previous publication,¹⁴ to find relevant additional or updated guidelines (see Supplementary material online, Table S2 ).

Study selection

Guidelines were excluded if they were focused on non-adult population or only made recommendation on pharmacological intervention.

Two independent reviewers (A.L., K.B.P.) assessed articles based on the title and the abstract and initial a priori inclusion and exclusion criteria used to conduct the database search were applied. Relevant guidelines were then assessed for full text review and extraction based on inclusion and exclusion criteria.

The Appraisal for Guidelines and Research Evaluation (AGREE) II tool¹⁵ was used to calculate the rigour of development score. A score of over 60% was deemed to represent a rigorously developed guidelines, in the context of addressing lifestyle modifications, and was required for inclusion in the final analysis.

Data extraction and quality assessment

The titles and abstracts of papers were assessed by two independent reviewers (A.L., K.B.P.). Any disagreement was settled by consensus or the impartial judgement of a third reviewer who arbitrated (C.M.). The same reviewers independently performed full data extraction into a prespecified extraction which included methods, patient groups and a summary of the lifestyle advice and intervention recommendations.

Data synthesis and analysis

Three reviewers (C.M., A.L., K.B.P.) extracted all the relevant recommendations from the guidelines that had an AGREE II score ≥ 60%. General lifestyle advice was the main emphasis of the data extraction. A recommendation matrix was produced.

Results

Our search retrieved 5890 titles, of which 140 titles were identified as potentially eligible. Based on the abstract review, we excluded 118 articles. After full article review, 12 more were excluded. We included 22 guidelines on hypertension. Figure 1 shows the PRISMA flow diagram highlighting the full inclusion and exclusion process.¹⁶ Ten guidelines had an AGREE score above the threshold of 60% and were included in the final extraction table. Table 1 summarizes the selected guidelines, along with rigour scores and conflicts of interest.

The areas of agreement and disagreement are summarized in Figure 2.

Supplementary material online, Table S3 shows the guidelines excluded based on their AGREE score.

Areas of agreement

Smoking

There was a consensus regarding the importance of smoking cessation advice. The only guidelines that did not have recommendations on smoking were the 2017 American College of Cardiology/American

Heart Association (ACC/AHA) ones as smoking was not included in the guideline’s clinical questions. All guidelines recommend offering referral to counselling services and pharmacotherapy. Most guidelines also emphasize avoidance of second-hand smoke.

Dietary sodium restriction

There was consensus regarding the anti-hypertensive effect of sodium restriction and the role of limiting salt intake in diet, not only in hypertensive patients but also as a measure of prevention of hypertension in the general population. Salt intake can be estimated from the 24-h urine collection measurement of sodium. Four of the selected guidelines recommended 5 grams of salt (approximately 2 grams of sodium) as thresholds of maximum daily amount. The AHA/ACC recommends less than 1.2 grams of sodium, equivalent to 3.8 grams of salt a day.

Interestingly, the Japanese Society of hypertension guidelines kept into consideration that the average daily intake of salt in their general population is one of the highest worldwide (>10 grams/day) and accept a threshold <6 grams/day for hypertensive patients. Similar advice is from other Asian guidelines (Korean and Chinese) and the Australian ones.

Potassium intake

There is evidence that potassium intake is inversely related to BP,^17,18 and that potassium-rich foods can help prevent and improve hypertension via different mechanisms including increased natriuresis, improved endothelial function and increased nitric oxide (NO) release, and inhibition of sympathetic activity.^19,20 Hence, eight guidelines recommend increased intake of potassium mainly by increasing dietary intake of fruit and vegetables, but not in patients at risk of hyperkalaemia (such as those with kidney failure or on mineralocorticoid receptor antagonists). The daily amount recommended is between 3.5 and 5 grams/day.

Dietary patterns

All guidelines recommend a healthy diet, rich in fresh fruit, vegetables, and whole grains, preferring low-fat dairy products, and with reduced content of saturated and total fat and red meats. The most recommended dietary patterns were the Mediterranean or the Dietary Approaches to Stop Hypertension (DASH) diet. Some guidelines mention the Nordic dietarian pattern, rich in oily fish.

Red meat

Most of the guideline recommendations suggest reduction of red meats in diet or recommend dietary patterns such as the DASH or Mediterranean diet, characterized by low weekly amounts of red meat, but do not have a specific recommendation section on red meats. Moreover, there was no specification regarding the maximum amount of weekly or monthly intake.

Fruit and vegetables, wholegrains

All guidelines recommend increased intake in the diet. Some guidelines advice on caution on intake of fruit in patients who are in the overweight/obese categories and those with known hyperkalaemia. International Society of Hypertension (ISH) and Qatar guidelines recommend abundant intake of vegetables rich in nitrates such as beetroot as they are known to lower BP. All guidelines included in this review make a general recommendation without specifying cut-offs or portions/servings.

Fish

All guidelines recement increase in fish intake as part of balanced diet, such as the Mediterranean diet. Only the Qatar Guidelines recommend an intake at least twice a week. Otherwise, the recommendations remain unspecific on the weekly amount.

Fats

There was consensus on the benefits of lowering dietary saturated and trans-saturated fat intake. The Australian guidelines specifically state that total fat intake should account to no more than 20–35% and total saturated and trans fats for no more than 10% of energy intake. Unsaturated fatty acids of vegetable origin, especially olive oil, are explicitly recommended in the diet for hypertensive patients in some guidelines.

Physical activity

All guidelines recommend regular physical activity, to lower BP and help with weight loss.

Exercise training can in fact improve the bioavailability of NO, endothelial function and attenuates insulin resistance.^21–23 All guidelines agree on aerobic exercise of moderate intensity. Recommended time per week dedicated to exercise varies between 150 and 350 min. Some guidelines discourage isometric exercise alone as this can cause an increase in BP, others specify the type of training (high intensity, high impact, aerobic vs. dynamic resistance).

Areas of disagreement

Body weight, body mass index, and body fat distribution

All guidelines recommend maintaining a healthy weight and avoiding a raised body mass index (BMI).

The ISH guidelines recommend ethnicity specific thresholds for BMI, keeping in consideration that some ethnic groups present higher cardiovascular risk even when patients are into ranges of weight considered safe for other ethnical groups.²⁴

Most guidelines recommend an ideal BMI < 25 kg/m², but only few emphasize the risks of abdominal obesity by stating specific cut-offs for abdominal circumference or a waist-to-height ratio <0.5.

Alcohol intake

All guidelines recognize an association between alcohol intake and raised cardiovascular risk profile or risk of hypertension, which is supported by strong evidence.²⁵

They recommend a reduction of alcohol intake and avoiding binge drinking. There is disparity on the maximum daily amount. For example, European Society of Hypertension recommends less than 14 units per week for men and less than 8 units per week for women, while the American, Canadian, and Australian guidelines recommend alcohol consumptions is 2 standard drinks/day for men and 1.5 for women (with standard drinks having different amount of alcohol content per guidelines).

Coffee and tea

Most guidelines recommend moderate intake of coffee and tea and discourage but provide different thresholds for what is considered as excess intake. There are over 1000 chemical compounds in coffee. The most studied ones such as caffeine can influence BP in both directions: whilst caffeine is known to have an acute effect on increasing BP, long term moderate caffeine consumption may have beneficial CV effects and it is not completely discouraged in any guideline. However, the conclusions on long term effects derive mainly from observational studies with very few randomized, controlled studies or meta-analyses.²⁶

Green or black tea consumption may also have a small but significant BP-lowering effect and some guidelines mention them as part of non-lifestyle dietary modifications.

Refined sugars and sweetened drinks

Only few guidelines directly mention sugars and sweetened soft drinks to be reduced in the diet.

Fibre intake

There was general recommended on increased dietary fibre intake, coming from fresh vegetables, fruit, and wholegrains. However, some guidelines mention the lack of supportive evidence of fibres effects on BP.

Nutrients and supplements

There is significant disparity among guidelines in terms of recommendation for specific nutrients and supplements. In most cases, the recommendation is that some specific dietary patterns such as DASH diet should be encouraged as they can provide a balanced intake of minerals, vitamins, and nutrients. However, there is no strong evidence that supplementation of specific nutrients may have any benefit on BP.

Supervised exercise

Specific recommendation for supervised exercise in patient with chronic conditions such as uncontrolled diabetes and hypertension, severe aortic stenosis and angina is only recommended in the Chinese guidelines for hypertension in geriatric patients.

Environmental factors like temperature, pollution

Very few guidelines mention the role of environmental factors. Only the ISH guidelines mention the potential of air pollution, and the Japanese and Chinese guidelines on the impact of cold temperature.

Psychological factors, meditation/yoga/relaxation

Psychological factors include individual-level processes and meanings that influence mental states, and psychological interventions are non-pharmacological interventions focused on these psychological factors.

While majority of guidelines recommend including questions about psychosocial stress when taking hypertensive patients’ history, only few guidelines mention that avoiding/reducing chronic emotional stress with relaxation techniques such as mindfulness and yoga, as evidence of their long-term benefits on hypertension is limited.

Sleep

All guidelines recommend including questions on sleep history and on apnoea. Some, like the Japanese ones, include poor quality/quantity sleep as possible contributing factor to raise BP and cardiovascular risk. The role of sleep apnoea as driver/causing factor of hypertension is emphasized in all guidelines and they all recommend its diagnosis if clinically suspected in symptomatic and/or overweight patients. However, only Chinese guidelines mention the importance of sleep (its duration and quality) in reducing BP and cardiovascular risk, alongside improving quality of life. Therefore, they include sleep as one of the lifestyle factors to address.

Discussion

We identified 10 rigorously developed hypertension guidelines that include recommendation on lifestyle changes and interventions as part of treatment or prevention of hypertension. We included all relevant international guidelines and did not limit our search to Western countries.

There was consensus between guidelines about the importance of lifestyle in hypertension treatment and cardiovascular risk reduction, and these non-pharmacological recommendations remain the treatment cornerstone of hypertension regardless its stage.

Smoking cessation, avoiding obesity, adequate physical activity levels, limiting salt and saturated fats, and having a plant-based diet that includes wholegrain and limit red meats are substantially shared between the guidelines.

Salt intake reduction is one of the most robust recommendations across guidelines. However, there are some differences in terms of cut-off of daily salt intake.

Sodium can affect BP by increasing water retention,²⁷ systemic peripheral resistances,²⁸ and affecting sympathetic activity and endothelial function.²⁹

Of note, assessment of daily salt intake can be difficult: the most accurate method remains the 24-h urinary sodium. In fact, about 94% of salt intake is excreted by kidneys. However, the day-to -day variability of salt intake can affect its accuracy if not repeated multiple times (at least in research settings). Other studies have tried to estimate sodium intake from spot urine Na measurements and validation of different formulas, but this can be less precise.

Reduction of salt intake can be difficult without implementation of public health measurements and governmental actions aimed at the food and beverage industry and reduction of salt and preservatives such as sodium glutamate.³⁰ In support to this, the SSaSS study proved the safety and efficacy of using a salt substitute (75% sodium chloride and 25% potassium chloride by mass) in 600 villages in rural China for almost 5 years, resulting in a significant reduction of cardiovascular outcomes and BP reduction.³¹

Obesity can directly cause hypertension via multiple mechanisms, such as activation of the sympathetic nervous system and renin-angiotensin-aldosterone system, increased inflammation, and insulin resistance.³² Visceral fat accumulation has a more significant impact on cardiovascular risk as it can affect glucose and fats metabolism and correlate to progression of atherosclerosis via metabolic and immunological mechanisms.^33–35 Nevertheless, assessment of visceral fat besides measurement of waist circumference is not adopted in routine clinical practice.

The dietary patterns recommended are slightly different, with the DASH diet and the Mediterranean one being the ones with stronger level of evidence (from randomized clinical trials) and therefore more often (though not unanimously) recommended.

The Mediterranean diet encourages intake of fruit, vegetables, cereals, nuts, and seeds, with olive oil as main source of fats vs. a low consumption of red meat and saturated fats.

The DASH study demonstrated that a diet rich in fruit, vegetables, and low-fat dairy products helped in reducing levels of total and saturated dietary fat and lowered BP.³⁶

The advice on intake of meat products is less clearly defined and more generic, and not uninformedly recommended among analysed guidelines. These areas may require further research for to enable more rigorous recommendation on their role in hypertension management.

Another significant area of disagreement includes the amount of sugar in the diet. High sugar intake may indirectly affect BP by inducing features of metabolic syndrome, including insulin resistance and impaired NO production. We also note a lack of recommendations on ultra-processed food, that is quite relevant in both rich, western countries and in lower income countries. Ultra-processed foods are defined as drink or food products made of several ingredients which, besides salt, sugar, oils and fats, include food substances not used in culinary preparations, in particular flavours, colours, sweeteners, emulsifiers and other additives used to replicate sensorial qualities of unprocessed or minimally processed foods or to mask unwanted qualities of the product.³⁷ They have high amounts of salt, total fat, saturated fat, and trans-fat, free sugar, and high energy density, and low fibre and micronutrients content. Of note, they contribute to more than half of all calories in the US diet.³⁸ While they contribute to obesity, due to its composition this type of food can also contribute directly to hypertension with some recent evidence supporting this.^39,40

Coffee intake is not discouraged in most guidelines, but recommended thresholds are different, and none of the guidelines mention the method of preparation. It is in fact known that different brewing methods affect the content of antioxidants and other components in coffee.^41,42

In reference to this, a recent study from Biobank UK has showed that moderate coffee consumption was associated with favourable cardiovascular outcomes, but also that regularly consuming decaffeinated coffee was associated with lower all-cause mortality as compared to zero coffee drinkers, suggesting that the benefit may only be partly attributable to caffeine content.⁴³

There were also differences identified in the recommendations thresholds for what is considered acceptable alcohol intake. Cut-offs for limited alcohol intake were generally based on a variable interpretation of observational studies.

The major points of disagreement among guidelines were inclusion of recommendation on novels factors that correlate to hypertension, including environmental factors like pollution or temperatures changes, and individual factors like stress and sleep, due to different levels of evidence.

Environmental factors may not be strictly considered as lifestyle factors or choices, and they could be more related to geographical place of living and have regional connotations which could be reflected in local guidelines.

The effects of environmental pollution on BP and cardiovascular risk are well known. Several meta-analyses have confirmed that increases in ambient fine particulate matter (PM_2.5) by 10 mg/m³ are associated with 1–3 mm Hg elevations in BP in the short term. Longer-term exposure is correlated to chronic hypertension, likely via endothelial dysfunction, systemic inflammation, autonomic imbalance.⁴⁴ This is particularly relevant because about 90% of world-wide population is exposed to pollution levels exceeding WHO air quality guidelines.⁴⁵

Another recent meta-analysis confirmed the association of particulate and gaseous air pollutants with hypertension, stronger in men than women and potentially modified by geographical and socio-economic factors.⁴⁶

Interestingly, despite evidence proving sex differences among lifestyle factors and effects on BP, guidelines do not currently discuss this.

Most evidence derives from small mechanistic and observational studies in public health, as it is hardly practical to design and conduct a randomized trial in the field. Nevertheless, only the International Society of Hypertension guideline mentions avoiding pollution as lifestyle measurement. This is likely due to society’s specific approach on developing practical global world-wide guidance, regardless of specific population or resources.

It could also be considered as general, world-wide factor that may require national and global changes and interventions rather than individual actions.

The International Society of Hypertension and the Japanese Hypertension Society guidelines are the only ones that mention the negative effect of cold temperatures on BP, and recommend avoiding cold, when possible, in hypertensive patients.

BP is known to have seasonal variations. Whilst it is generally known that cold may raise BP, and that during winter the cardiovascular risk of single individuals and populations is higher, warm weather may have effects on BP in both directions: in warm seasons BP may be lower, but patients may also observe an increase due to lack of sleep or sense of unease.⁴⁷ This is particularly relevant in connection with global warming. The lack of recommendation in other guidelines on avoiding cold is due to lack of robust evidence from trials and only due to evidence from observational studies. Moreover, one could speculate that climate related effects on hypertension are not influenced by personal choices and could not be considered strictly as lifestyle intervention targets.

Depression and anxiety have a close relationship with hypertension and cardiovascular disease with a prevalence of about 30% among hypertensive patients.⁴⁸ Interestingly, a recent study found a positive effect of use of 9 antihypertensive agents on risk of depression .⁴⁹

Similar to previous systematic review findings for cardiovascular risk reduction in general, only few guidelines recommend assessing and avoiding stress or include relaxation techniques in a multidisciplinary, comprehensive management of hypertension.⁷

Few trials have been published on the subject: for example, the HARMONY study was a randomized, controlled trial examining the efficacy of an 8-week mindfulness-based stress reduction programme for BP lowering among unmedicated stage 1 hypertensive participants.⁵⁰ However, the numbers of participants enrolled remained quite small. Other trials included yoga/psychological factors as part of multiple synchronous interventions including diet and exercise, therefore it is difficult to generalize, extrapolate guidance from these trials.⁵¹

Strengths and limitations

To the best of our knowledge, this is the first systematic review focused on the non-pharmacological intervention recommendation included in contemporary international hypertension guidelines that were rigorously developed. We did not limit the guidelines to those developed from Western countries or developed continents, but also global guidelines and guidelines from Asian and Middle Eastern countries, which would keep in mind the diversity of lifestyles, habits, and ethnicity-related cardiovascular risk differences.

Although we assessed the guideline development process, we did not assess the clinical validity of the recommendations as this is not currently included in the AGREE II instrument and as it was beyond the scope of this review. We focused lifestyle interventions and advice and not pharmacotherapy to avoid overlap with previous publications in this area.

Another limitation is given by the fact that our search strategy only included single interventions and did not include any holistic lifestyle change programme. A global approach (diet plus exercise, salt reduction and weight loss for example) has been proved to be more effective than single interventions on one habit or risk factor, and this is mentioned in most of the guidelines included in this review.

Conclusions

Current guidelines agreed on the importance of non-pharmacological factors in the management of hypertension including lifestyle advice and interventions. There was consensus on recommendations for numerous factors such as limiting dietary salt intake, increased physical activity, smoking cessation and dietary patterns, as key components in the management of hypertensive patients but also as part of public health measurements.

Recommendations on psychological factors, role of food supplements, sleep, sex differences and environmental factors are currently limited and may require further study to enable clearer recommendation in the guidelines.

Supplementary material

Supplementary material is available at European Journal of Preventive Cardiology online.

Acknowledgements

C.M. and M.Y.K. contributed to the conception or design of the work.

Data availability

The data underlying this article are available in the article and in its online supplementary material. Any additional data will be shared on reasonable request to the corresponding author.

References

Author notes