Long-term effects of weight-reducing diets in hypertensive patients

  • Review
  • Intervention

Authors


Abstract

Background

All major guidelines for antihypertensive therapy recommend weight loss. Thus dietary interventions that aim to reduce body weight might be a useful intervention to reduce blood pressure and adverse cardiovascular events associated with hypertension.

Objectives

Primary objectives

To assess the long-term effects of weight-reducing diets in hypertensive patients on

-   all cause mortality
-   cardiovascular morbidity
-   adverse events (including total serious adverse events, withdrawal due to adverse events and total non-serious adverse events)

Secondary objectives

To assess the long-term effects of weight-reducing diets in hypertensive patients on

-   change from baseline in systolic blood pressure
-   change from baseline in diastolic blood pressure
-   body weight reduction

Search methods

Studies were obtained from computerised searches of Ovid MEDLINE, EMBASE, CENTRAL and from searches in reference lists and systematic reviews.

Selection criteria

Randomised controlled trials (RCT) in adult hypertensive patients were included if they had a study duration of at least 24 weeks and compared weight reducing dietary interventions to no dietary intervention in adult patients with primary hypertension.

Data collection and analysis

Two authors independently assessed risk of bias and extracted data. Studies were pooled using fixed-effect meta-analysis. In case of moderate or larger heterogeneity as measured by Higgins I2, a random effects model was used.

Main results

Eight studies involving a total of 2100 participants with high blood pressure and a mean age of 45 to 66 years met our inclusion criteria. Mean treatment duration was 6 to 36 months. No study included mortality as a pre-defined outcome. One RCT evaluated the effects of dietary weight loss on a combined endpoint, consisting of the necessity of reinstating antihypertensive therapy and severe cardiovascular complications. In this RCT weight reducing diet lowered the endpoint, hazard ratio 0.70 (95% confidence interval [CI], 0.57 to 0.87) compared to no diet. None of the studies evaluated adverse events as designated in our protocol. Blood pressure was reduced in patients assigned to weight loss diets as compared to controls: systolic blood pressure (SBP): weighted mean difference (WMD): -4.5 mm Hg; 95% CI, -7.2 to -1.8 mm Hg (3 of  8  studies included in analysis), and diastolic blood pressure (DBP): WMD -3.2 mm Hg; 95% CI, -4.8 to -1.5 mm Hg (3 of  8  studies included in analysis). Patients' body weight was also reduced in dietary weight loss groups as compared to controls, WMD of -4.0 kg (95% CI: -4.8 to -3.2) (5 of  8  studies included in analysis). Two studies used withdrawal of antihypertensive medication as their primary outcome. Even though this was not considered a relevant outcome for this review, the results of these studies strengthen the finding of reduction of blood pressure by dietary weight loss interventions.

Authors' conclusions

In patients with primary hypertension, weight loss diets reduced body weight and blood pressure, however the magnitude of the effects are uncertain as a result of the small number of patients and studies that could be included in the analyses. It is not known whether weight loss reduces mortality and morbidity. No useful information on adverse effects was reported in the relevant trials.

アブストラクト

高血圧患者における体重減少食事療法の長期的効果

背景

降圧療法に関する主要なガイドラインのすべてが体重減少を推奨している。よって、体重減少を目的とする食事介入は、血圧を下げ高血圧に合併する心血管系有害事象を減少させる有用な介入の1つであると考えられる。

目的

主要目的高血圧患者における体重減少食事療法の長期的効果を評価すること。-総死亡率-心血管系罹病率-有害事象(重篤な有害事象すべて、有害事象による中止、非重篤な有害事象すべてを含む)副次目的高血圧患者における体重減少食事療法の長期的効果を評価すること。-収縮期血圧のベースラインからの変化-拡張期血圧のベースラインからの変化-体重減少

検索戦略

Ovid MEDLINE、EMBASE、CENTRALのコンピュータ検索、および参照文献リストとシステマティック・レビューの検索から研究を入手した。

選択基準

研究期間が24週以上で原発性高血圧成人患者を対象に体重減少食事療法による介入がある場合と、食事による介入のない場合を比較しているランダム化比較試験(RCT)

データ収集と分析

2名のレビューアが別々にバイアスリスクを評価しデータを抽出した。研究は固定効果メタアナリシスを用いて統合した。Higgins I2により測定した異質性が中等度以上の場合は、ランダム効果モデルを用いた。

主な結果

平均年齢45~66歳の高血圧患者総数2,100例を対象にした8件の研究が選択基準を満たした。平均治療期間は6~36カ月であった。事前に規定したアウトカムとして死亡率を含む研究はなかった。1件のRCTは、前の降圧療法の再開の必要性と重度の心血管系合併症からなる複合エンドポイントに対する体重減少食事療法の効果を検討していた。このRCTにおいて、体重減少食事療法によりエンドポイントが減少し、食事療法がない場合に比べてハザード比は0.70 [95%信頼区間(CI)0.57~0.87]であった。今回のプロトコルで規定した有害事象を評価した研究は認められなかった。血圧はコントロール群に比べて体重減少食事療法群で低下した[収縮期血圧(SBP):重み付け平均差(WMD)-4.5 mm Hg、95% CI -7.2~-1.8 mm Hg(8件中3件で解析)、拡張期血圧(DBP):重み付け平均差(WMD)-3.2 mm Hg、95% CI -4.8~-1.5 mm Hg(8件中3件で解析)]。患者の体重もコントロール群に比べて体重減少食事療法群で減少した[WMD -4.0 kg(95% CI -4.8~-3.2)(8件中5件で解析)]。2件の研究は、主要アウトカムとして、降圧薬の中止を用いていた。本レビューではこれを関連性のあるアウトカムとして考えていなかったが、これらの研究結果は、体重減少食事療法による介入によって血圧を低下させるという所見の重要性を強調している。

著者の結論

原発性高血圧患者では、体重減少食事療法により体重および血圧が低下したが、本解析に選択できた患者および研究の数が少なかったため、その効果の大きさは不明である。体重減少が死亡率および罹病率を低下させるかどうかは不明である。有害作用に関する有用な情報は、関連性のある試験において報告されていない。

訳注

監  訳: 相原 守夫,2011.12.15

実施組織: 厚生労働省委託事業によりMindsが実施した。

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Plain language summary

Weight reducing diets for patients with elevated blood pressure

Compared to the general population, patients with high blood pressure have a higher risk for death and complications such as heart attack or stroke. Based on the association of increased weight and increased blood pressure, dietary interventions to lower body weight are commonly recommended as a first therapeutic step for overweight patients with high blood pressure. However, whether weight loss has a long-term effect on blood pressure and reduces the adverse effects of elevated blood pressure remains unclear. As only randomised controlled trials (RCT) comparing groups with and without a weight reducing diet can answer these issues, we only included RCTs in our systematic review. 30 articles reporting on eight studies met the inclusion criteria. The 8 included studies involved a total of 2100 participants with high blood pressure and a mean age of 45 to 66 years. Mean treatment duration was 6 to 36 months and there was little or no information about deaths or other long-term complications. In three of eight studies, effects on systolic and diastolic blood pressure were provided, showing that systolic and diastolic blood pressure were reduced by weight loss interventions by 4.5 mm Hg and 3.2 mm Hg, respectively. Five out of eight studies reported body weight, and weight loss interventions reduced weight by 4.0 kg as compared to controls. No useful information on possible adverse effects was reported in the included trials.
In conclusion, there is no evidence for effects of weight loss diets on death or long-term complications and adverse events. In addition, results on blood pressure and body weight could be considered uncertain, because not all studies were included in the analyses. But these results are mainly based on one large study with about 600 participants that was judged to be of high quality, and the fact that most of the other studies excluded from analysis indirectly (e.g. via successful withdrawal of blood pressure reducing drugs) further underline these effects, gives confidence in the obtained results.

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