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 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 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 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.