Research Letter

Journal of Human Hypertension (2008) 22, 138–140; doi:10.1038/sj.jhh.1002275; published online 6 September 2007

Contemplative meditation reduces ambulatory blood pressure and stress-induced hypertension: a randomized pilot trial

J P Manikonda1,4, S Störk1,4, S Tögel1, A Lobmüller1, I Grünberg2, S Bedel3, F Schardt3, C E Angermann1, R Jahns1 and W Voelker1

  1. 1Department of Internal Medicine I, Center of Cardiovascular Medicine, University of Würzburg, Würzburg, Germany
  2. 2Center for Contemplative Meditation, Würzburg, Germany
  3. 3Department of Medicine I, Betriebsärztliche Untersuchungsstelle, University of Würzburg, Würzburg, Germany

Correspondence: S Störk, E-mail: stoerk_s@klinik.uni-wuerzburg.de

4These authors share the authorship of this paper equally.

A total of 52 pharmacologically untreated subjects with essential hypertension were randomly allocated to either 8 weeks of contemplative meditation combined with breathing techniques (CMBT) or no intervention in this observer-blind controlled pilot trial. CMBT induced clinically relevant and consistent decreases in heart rate, systolic and diastolic blood pressure if measured during office readings, 24-h ambulatory monitoring and mental stress test. Longer-term studies should evaluate CMBT as an antihypertensive strategy.

Emotional and psychological stress is an acknowledged risk factor and mediator of hypertension,1, 2 but it is still unknown whether stress-reducing techniques may effectively control essential hypertension.3, 4, 5 Numerous stress-reducing techniques have been investigated, as physical techniques (for example, progressive muscle relaxation, breathing exercises, yoga), cognitive and behavioural therapies (for example, talk therapies, meditation, guided imagery), stress management (for example, autogenic training) and biofeedback.5 Some of these techniques share common features (for example, breathing control) but may exert their effects via different underlying mechanisms. Contemplative meditation as a stress-reducing technique has been widely studied with divergent results. A recent systematic review of randomized clinical trials summarized that, at present, there is insufficient evidence to conclude whether or not meditation has a cumulative positive effect on blood pressure (BP).3 We therefore aimed to determine in a randomized controlled observer-blind pilot trial the differential effects of contemplative meditation combined with breathing techniques (CMBT) on BP at rest, ambulatory and during mental stress.

Meditation-naïve subjects with pharmacologically untreated BP were sought by newspaper advertisements (n=81). They qualified for screening (n=64) in our cardiovascular outpatient department if their sitting BP after 5min of rest was >140mm Hg systolic and/or >85mm Hg diastolic on each of three occasions within 4 weeks. Important exclusion criteria were BP levels >180mm Hg systolic and/or 110mm Hg diastolic and secondary hypertension. A total of 52 subjects were randomized 1:1 into 8 weeks of CMBT or no intervention. All subjects received the lifestyle counselling recommended by current guidelines on one occasion.1, 2 In the CMBT group, two 40-min sessions were held in the early morning and the evening. The first phase (10–12min) prepared the participants for the session and focussed on breathing exercises, that is, slow abdominal breathing to achieve a general muscle tension release.6, 7 The second phase (30min) dealt with exercising meditation techniques based on the Christian tradition.8, 9 Eight weeks after randomization, all baseline examinations were repeated at the same time of the day in a single participant. At the day of baseline and follow-up examination, study participants refrained from coffee, smoking and physical exercise. Office BP was measured four times each 5min apart on the left upper arm with an oscillometric-automated device (DINAMAP 8100, Critikon) after 10min rest in the sitting position, and the mean of the last three measurements was calculated. Twenty-four hours BP recording was performed using calibrated devices (Custo Screen 100, custo med GmbH, Ottobrunn, Germany). Day and night time was specified by the subject on a diary sheet. A standardized computerized version (developed by Stefan Bedel) of the concentration test Konzentrations–Leistungs-Test (KLT) according to Düker was used. Participants were seated in a quiet air-conditioned room using ear plugs to minimize distraction. All tests were performed between 1400 and 1600 hours. The KLT consists of 250 analogously built simple arithmetic procedures mimicking conditions of office work stress. The impossibility to accomplish all procedures within the available time frame generates a high and reproducible level of stress. Heart rate and BP were measured every 5min during the mental stress test (duration 30min) and for 20min before and after completion. To compare the effects between groups and mental stress test periods, the averages of three time points before, seven time points during and four time points after the test completion were used. The primary end point of the trial was prespecified as the comparison between groups of the median change from baseline to follow up in systolic BP during mental stress (that is, the average of the seven measurement points). Sample size analysis suggested that 26 participants were needed to show a difference between groups with a power of 0.90, alpha of 0.05 and a drop-out rate of three subjects per group. Non-parametric tests were used to compare groups.

Groups were not different regarding the baseline characteristics shown in Supplementary Table 1. No subject in the CMBT group but three controls (two females) dropped out. Adherence to the study protocol in the CMBT group was >90% of all sessions. With CMBT, the median (%) change in resting office systolic BP after 8 weeks of meditation was −15mm Hg (−11%) vs 3mm Hg (0%) in controls (P<0.0001; Supplementary Table 2). Further, a significant reduction of diastolic BP (−13 vs −2%) and a trend for heart rate (−13 vs 0%) was observed. At follow-up, 75% of the subjects in the CMBT group but none of the controls had office BP levels <130mm Hg systolic/<80mm Hg diastolic. Consistently, in the CMBT group, ambulatory BP recordings showed absolute median reductions of 4–7mm Hg for systolic and diastolic BP values for day and night time periods (all Pless than or equal to0.005 for comparison of change between groups; Supplementary Table 2). At follow-up, 50% of subjects in the CMBT group, but none of the controls, had total mean BP levels <125mm Hg systolic/75mm Hg diastolic. Mental stress test induced an immediate sympathetic activation indicated by a sustained rise of systolic BP in both groups during the 30-min test period (Supplementary Table 2 and Figure 1a). At follow-up, this increase was still evident in both groups, but the averaged BP during mental stress was 11mm Hg lower in the CMBT group compared with controls: median (%) change −18mmHg (−12%) vs −7mmHg (−5%; P=0.002), respectively. The raw data and the result of the primary end point are shown in Figures 1b and c.

Figure 1.
Figure 1 - Unfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, please contact help@nature.com or the author

(a) The time course of systolic BP behaviour at baseline and follow-up during mental stress test in the intervention and control group. Boxes (baseline) and circles (follow-up) indicate means with standard errors. (b) Effect of meditation combined with breathing techniques on BP during mental stress test (that is, average of 7 BP measurements). The panels show individual systolic (top) and diastolic (bottom) BP levels at baseline and follow-up. Large square boxes indicate means±s.e.m. P-value for within-group comparison (Wilcoxon's test). (c) The change of systolic (top) and diastolic (bottom) BP levels between baseline and follow-up within each study group. Square boxes indicate box and whisker plots. P-value for between-group comparison of median BP changes from baseline to follow-up (Mann–Whitney U-test). BP, blood pressure.

Full figure and legend (182K)

This pilot trial indicates that CMBT may effectively lower BP levels in essential hypertension under resting conditions and during mental stress. The observed antihypertensive effects of CMBT were substantial, of similar magnitude compared with pharmacotherapeutic trials,10 sustained during day and night and were achieved in the majority of meditating subjects. A median difference in office BP between the intervention and the control group of 18mm Hg was found. This is compatible with a potentially pronounced risk reduction for stroke and myocardial infarction, because an increment of 20mm Hg in systolic BP office readings in middle-aged persons is associated with a twofold increase in cardiovascular mortality.11 In both groups, BP values during mental stress at follow-up were lower, either because the participants became accustomed to the stress situation or due to effects of regression towards the mean. The absolute increase in systolic/diastolic BP during mental stress was in the same order of magnitude as observed previously in healthy controls. However, at follow-up, meditating subjects started from a lower pre-test BP and maintained lower BP levels throughout the stress and post-test period. Both meditation and breathing techniques are thought to shift the sympathetic/vagal balance towards a vagal stimulation. Our trial design did not allow studying the differential effects of meditation8, 9, 12 and breathing.6, 7 It is possible that the BP-lowering effect of meditation may attenuate or dissipate if the intensity or frequency of meditation sessions decreases. Any meditation technique is likely to have a substantial placebo effect. Since no validated ‘sham meditation technique’ is available, this feature was not included into the study design. However, we aimed to avoid the previously identified methodological shortcomings of meditation research.3 The beneficial effects of CMBT may be achievable with less intense protocols and may also induce indirect effects as better compliance with pharmacotherapy. Future studies should address the long-term effects of CMBT on BP as a stand-alone treatment or as adjunct to pharmacological therapy.

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References

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Supplementary Information accompanies the paper on the Journal of Human Hypertension website (http://www.nature.com/jhh)

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