Deep Dive: The best non-drug ways to lower blood pressure

Hypertension, a condition characterized by elevated blood pressure, is one of the largest modifiable risk factors for cardiovascular disease. Hypertension is prevalent in almost 30% of the entire U.S. population, with both men and women affected equally. Blood pressure management is one of the primary interventions used to reduce the risk of cardiovascular disease and stroke. While pharmacotherapy with antihypertensive drugs^[1] is effective for managing blood pressure, other nondrug interventions such as diet, exercise, and stress management have also been shown to be effective.

Numerous randomized controlled trials of nondrug interventions, such as diet^[2] and exercise^[3], have shown efficacy for lowering blood pressure. The effects of these interventions have previously been compared to drug based interventions and some, as shown in Figure 1, have been demonstrated to be as effective^[4] as drug based therapies alone, at least in people with systolic blood pressures above 150 mmHg. While these interventions have been compared to pharmacotherapy before, the effectiveness of the different nondrug interventions have not been systematically compared to each other. The present study was a meta-analysis comparing various nondrug interventions and their absolute and relative effectiveness at lowering blood pressure in people with primary hypertension and prehypertension.

Figure 1: Systolic pressure reduction in people with SBP of at least 150 mmHg (with 95% confidence intervals)

References: Naci et al. Br J Sports Med. 2019 Jul.^[5]
Juraschek et al. J Am Coll Cardiol. 2017 Dec.^[4]

Hypertension affects up to 30% of the entire U.S. population and is one of the leading risks for cardiovascular disease. Reduced blood pressure can be achieved through antihypertensive drugs, or through various nondrug interventions, such as diet, exercise, and stress management. The present meta-analysis under review compared the effectiveness of various nondrug interventions on lowering blood pressure in people with primary hypertension and prehypertension.

The present study was a network meta-analysis of randomized controlled trials that were at least four weeks in duration and compared various nondrug interventions for lowering blood pressure in people with primary hypertension (hypertension without a known secondary cause) or prehypertension. Network meta-analyses allow researchers to indirectly compare interventions that were not directly compared in the underlying trials. The meta-analysis was reported according to PRISMA^[6] guidelines but was not preregistered.

This study included randomized controlled trials in adults (18 years or older) with primary hypertension or prehypertension. Hypertension in participants not taking antihypertensive medication was defined as a systolic blood pressure of at least 140 mmHg and/or diastolic blood pressure of at least 90 mmHg. Participants with established hypertension using antihypertensive medication were considered to have hypertension even if their blood pressure was less than 140/90 mmHg. Prehypertension was defined as a systolic blood pressure of 120–139 mmHg and/or diastolic blood pressure of 80–90 mmHg. Trials were included in the meta-analysis if they used a nondrug intervention and either other nondrug therapies or usual care (no change in lifestyle) as a control. Studies were excluded if they included participants with a history of heart failure, renal disease, stroke, mental illness, diabetes, or metabolic syndrome. The exclusion of participants with metabolic syndrome is surprising because a lot of people with high blood pressure also have metabolic syndrome.

The primary endpoints of this meta-analysis, which were treated as co-primary endpoints, were reductions in systolic and diastolic blood pressure, assessed using mean differences. Additionally, risk of bias was assessed using the Cochrane risk of bias tool^[7] and the quality of evidence was assessed using the GRADE^[8] criterion. Heterogeneity was assessed using an I² statistic.

The study under review was a systematic review and network meta-analysis of nondrug interventions for lowering blood pressure in people with primary hypertension or prehypertension. The meta-analysis included studies that used nondrug interventions and compared them to other nondrug interventions and/or usual care. The study adhered to PRISMA guidelines and reported the quality of evidence and risk of bias.

There were a total of 14,923 participants across 126 randomized controlled trials included in the network meta-analysis. These studies covered 22 nondrug interventions, including dietary modification, physical exercise, stress reduction, weight loss, alcohol restriction, lifestyle modification, and combination interventions.

The network meta-analysis showed that 10 interventions were more effective at lowering systolic and diastolic blood pressure than usual care. When researchers compared interventions focused on systolic blood pressure, they found 15 interventions to be more effective than usual care. When comparing interventions focused on diastolic blood pressure, the researchers found 12 interventions to be more effective than usual care. The list of these interventions and their effects compared to usual care are detailed in Figure 2. Of the nondrug interventions, Tai Chi, following a DASH diet, aerobic exercise, and following a low-sodium and high-potassium diet appeared to have the largest effect among the nondrug interventions.

Figure 2: Effects on systolic and diastolic blood pressure plus evidence levels (with 95% confidence intervals)

The GRADE quality of evidence ranged from very low to high depending on the intervention, with the highest levels of quality seen for the DASH diet, comprehensive lifestyle modification, salt restriction, and meditation, while the lowest quality was seen in the aerobic exercise and DASH diet combination intervention, as well as the yoga-based intervention. Furthermore, while the Tai Chi intervention had the largest effect size, it also reported a low quality of evidence. See Figure 2 for a full list of the interventions and their level of evidence.

There was substantial heterogeneity (more than 70%) for both systolic and diastolic blood pressure in people with primary hypertension and in people with prehypertension. Sensitivity analysis did not change the rankings of the effects and the meta-regression found that the covariates of age, BMI, proportion of people using antihypertensive medications, and gender did not affect the results of this study.

Nondrug interventions appeared to be effective for lowering blood pressure with dietary modifications, with the DASH diet and salt/sodium restriction having the most evidence to support their effects. Other interventions, such as lifestyle modification and meditation, also effectively lowered blood pressure. Other interventions showed a benefit but had lower levels of evidence. The effectiveness of the interventions ranged from reductions of about 1 mmHg to about 10–15 mmHg.

The present meta-analysis suggests that several nondrug interventions are effective for lowering both systolic and diastolic blood pressure. The interventions that show efficacy ranged from dietary interventions, to exercise interventions, to stress management. The populations that these interventions showed improvement for covered a wide range of ages, socioeconomic status, as well as race and ethnicity. The present study was also the first to compare the efficacy of these nondrug interventions with one another, as well as compare the effects to usual care.

The nondrug interventions examined in the present study lowered systolic blood pressure by anywhere from approximately 1 mmHg up to approximately 13 mmHg. By comparison, antihypertensive^[9] drugs lower systolic blood pressure by up to 15 mmHg, depending on the class of drug and baseline blood pressure. Note that the present study was conducted to compare the effects of these nondrug interventions to each other, and not against drug/pharmacotherapy based interventions. As such, it is difficult to determine the efficacy of these interventions directly against or as adjuvants to pharmacotherapy.

The interventions ranged in both the magnitude of their effects as well as the strength of the evidence in support of them. For example, the present study found that the DASH diet, a diet covered previously in Study Deep Dives, characterized by increased fruit and vegetable intake and modest protein intake (15–20% of total calories), had the best evidence for reducing both systolic and diastolic blood pressure. The use of the DASH diet intervention was supported by high quality evidence, according to the GRADE criteria, and was shown to lower systolic and diastolic blood pressure by about 8 mmHg and about 4.5 mmHg, respectively. Other interventions, such as Tai Chi, showed a larger effect size (about 13 mmHg), but had a much lower quality of evidence. When both the magnitude of the effect and the strength of the evidence are taken into consideration, the DASH diet, low calorie diets, mediation, and salt restriction appeared to be the most effective forms of nondrug interventions for managing blood pressure. Several of the combination interventions (e.g. low calorie diet plus exercise) had lower levels of evidence and showed much less precise measures for their effects than singular interventions, possibly due to fewer and/or smaller trials.

To understand these findings in the context of heart disease, it is important to look at how lowering blood pressure can reduce the risk of cardiovascular disease, death from cardiovascular disease and all-cause mortality. For example, one meta-analysis^[10] found that reducing blood pressure from approximately 140 mmHg to 130 mmHg reduced the risk of major cardiovascular disease by 17%, but this risk was reduced by 42% when blood pressure was lowered to approximately 120 mmHg. Interventions in the present study, such as DASH, low calorie diets, salt restricted diets, and meditation may lower the risk of major cardiovascular disease by about 10–20%, or more, depending on the effect of the intervention on blood pressure.

It is important to keep in mind that these studies did not exclude people who were taking antihypertensive medication. Roughly a third of all participants were taking antihypertensive medication, and a meta-regression showed that the use of antihypertensives did not substantially change the results. As such, the present interventions can be used in conjunction with standard of care pharmacotherapy. In fact, combining pharmacotherapy with nondrug interventions may be more beneficial than either intervention by itself. For example, one study^[11] found that a combination of a low-sodium diet with an angiotensin converting enzyme (ACE) inhibitor lowered blood pressure beyond the effects of just the ACE inhibitor, and that this combination was as effective as a combination of the ACE inhibitor and a thiazide diuretic. These results may not apply to all pharmacotherapies, as different drugs have different mechanisms of action and may not work synergistically with nondrug interventions.

There are several limitations of the present study that should be taken into consideration when interpreting the findings. First, not all of the interventions were compared to usual care. Second, there were no direct comparisons to pharmacotherapies in the input studies, which can make it difficult to understand the effects of these interventions under controlled conditions. Third, there was no analysis of different classes of antihypertensives in the subgroup analysis or meta-regression. Some antihypertensives may work on the same pathways to lower blood pressure as many nondrug interventions (e.g. salt restrictive diets and diuretics). Finally, a network meta-analysis does not provide the same level of evidence as directly comparing interventions in a randomized controlled trial because a network meta-analysis involves several assumptions.

The present study supports the use of a wide range of nondrug interventions for lowering blood pressure, with strong evidence for the DASH diet, lifestyle modification, meditation, and low calorie diets. These interventions may be used in combination with pharmacotherapies and can produce reductions in blood pressure that have been associated with significant reductions in cardiovascular disease risk.

Q. What specific nutrients lower blood pressure?

Besides the restriction of sodium, there are some nutrients that may help lower blood pressure. For example, one meta-analysis^[12] found that supplementation of potassium lowered blood pressure by about 4–5 mmHg. Beetroot juice^[13] may also lower blood pressure, which may be partially driven by nitrate content^[14], but also by mechanisms independent of nitrate. Garlic also probably lowers blood pressure in people with hypertension. The form doesn't seem to matter much for lowering systolic blood pressure, but garlic powder may outperform aged garlic extract when it comes to lowering diastolic pressure.^[15]

Q. Is cardio or resistance training better for lowering blood pressure?

Both aerobic and resistance^[16] training have been shown to have some effect on blood pressure. However, it appears that aerobic training performed regularly is the most effective form of exercise for lowering blood pressure.

This systematic review and meta-analysis indicates that multiple nondrug interventions are effective for reducing blood pressure among people with primary hypertension and prehypertension. The effect of these interventions range from minor reductions (about 1 mmHg) to substantial reductions (about 10–15 mmHg), depending on the intervention. Dietary modifications, such as following a DASH diet, a sodium restricted diet, or a low calorie diet, followed by stress management through meditation or other practices, are likely to be the most beneficial. These interventions can be effective and important components of a holistic approach to reducing blood pressure, and can also complement conventional drug-therapy for hypertension.