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From the Georgia Institute for Prevention of Human Diseases and Accidents (V.A.B., H.C.D., F.A.T.), Department of Pediatrics (V.A.B., F.A.T.), and Department of Psychiatry (F.A.T.), Medical College of Georgia, Augusta, GA; and Tutt Middle School, Augusta, Georgia (J.B.M.).
Address correspondence and reprint requests to Frank A. Treiber, Ph.D., Georgia Prevention Institute, Bldg. HS1640, Medical College of Georgia, Augusta, GA 30912. E-mail: ftreiber{at}mail.mcg.edu
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMETHODSRESULTSDISCUSSIONACKNOWLEDGMENTSREFERENCES |
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METHODS: Data from 73 middle school students (age 12.3 ± 0.6 years) randomly assigned by classroom to either meditation (N = 34) or health education control (N = 39) groups were analyzed. The meditation groups engaged in 10-minute sessions at school and at home after school each day for 3 months. Resting (seated) systolic blood pressure, diastolic blood pressure, and heart rate measurements were obtained pretest and posttest on three consecutive school days using Dinamap 1846SX monitors. Ambulatory systolic blood pressure, ambulatory diastolic blood pressure, and ambulatory heart rate were recorded over 24-hour periods at pretest and posttest every 20 minutes during self-reported normal waking hours and every 30 minutes during self-reported normal sleep hours using Spacelabs 90207 monitors.
RESULTS: Significant (p < .05) differences in average change from pretest to posttest were found between the meditation and health eduction control groups for resting systolic blood pressure (–2.7 vs. 1.1 mm Hg), daytime ambulatory systolic blood pressure after school (–2.0 vs. 3.6 mm Hg), daytime ambulatory diastolic blood pressure after school (0.1 vs. 4.3 mm Hg), and daytime ambulatory heart rate after school (–5.3 vs. 0.3 bpm).
CONCLUSION: These findings demonstrate the potential beneficial impact of meditation on blood pressure and heart rate in the natural environment in healthy normotensive youth.
Key Words: youth, • blood pressure monitoring, • ambulatory, • meditation, • clinical trial.
Abbreviations: AA = African American;; ABP = ambulatory BP;; ANOVA = analysis of variance;; BP = blood pressure;; bpm = beats per minute;; CA = Caucasian;; CTL = health education control;; CVD = cardiovascular disease;; DBP = diastolic blood pressure;; EH = essential hypertension;; HR = heart rate;; HPA = hypothalamic-pituitary-adrenocortical;; MANOVA = multivariate analysis of variance;; MED = meditation;; MBSR = Mindfulness-Based Stress Reduction;; PMR = progressive muscle relaxation;; SBP = systolic blood pressure;; SNS = sympathetic nervous system;; TM = Transcendental MeditationTM.
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INTRODUCTION |
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Psychosocial stress has been posited as playing a role in the development of EH (10,11). Stress reduction approaches may prove beneficial in the reduction of BP in youth. To date, few studies have evaluated stress reduction interventions on BP in prehypertensive youth, but findings have been encouraging. Progressive muscle relaxation (PMR) training was shown to reduce systolic BP (SBP) relative to controls after 3 months (–7.2 vs. –1.9 mm Hg) in predominantly white adolescents (12). Transcendental MeditationTM (TM) reduced daytime SBP and diastolic BP (DBP) at 2-month and 4-month evaluations and at 4-month follow-ups (average change across evaluations: –3.9 vs. –0.9 mm Hg for SBP; –2.4 vs. –0.1 mm Hg for DBP) compared to a health education control group in AA adolescents (13). Notably, both of these studies involved youth with high normal BP levels (ie, 85th to 95th percentile).
Recent epidemiologic studies have found BP levels to be monotonically associated with future CV morbidity and mortality (14). For example, adult normotensives (ie, SBP/DBP 120–129/80–84 mm Hg) have 40% increased risk and those with high normal BP levels (130–139/85–89 mm Hg) are at more than twice the risk of developing CVD, compared to adults with optimal BP (<120/<80 mm Hg) (14). Related to this, the recent JNC-7 report identified the need for nonpharmacological intervention in those groups who heretofore were not considered "at risk" for development of CVD. Furthermore, those with normal (prehypertensive) and optimal BP are encouraged to make lifestyle modifications to further reduce their risk of developing CVD (15). Research with adult long-term practitioners of TM has shown that they have significantly lower BP compared to age group-based population norms (16). Whether meditation programs will benefit BP levels in youth with normal BP is unknown.
Four controlled and seven uncontrolled adult studies on mindfulness-based stress reduction (MBSR) indicate effectiveness in reducing stress, anxiety, and depression (17). To date, no published studies have examined the impact of the simple breathing meditation component of MBSR on BP (17). Based on previous findings with adults (18) and with adolescents (13,19) practicing TM, it was predicted that youth who practiced meditation would exhibit greater decreases in resting and ambulatory BP from pretest to posttest.
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METHODS |
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Measures
All testing was conducted at the school except for the ambulatory BP (ABP) measurements, which were obtained during school and nonschool hours. Height (via stadiometer) and weight (via Detecto scale, Cardinal Scale Manufacturing Co., Webb City, MO) measurements were recorded using established protocols (19). Resting seated SBP, DBP, and heart rate (HR) were recorded from the right arm using Dinamap 1846SX monitors (Critikon, Inc., Tampa, FL) for 10 minutes (four readings at minutes 0, 5, 7, and 9) on three consecutive school days both before (pretest) and after treatment (posttest). The first measurement each day was discarded, and the other three measurements were averaged. The minimal daily average was used at both pretest and posttest as the basal resting measurement. Based on norms for age, height, and gender (20), no participants were found to be hypertensive (ie, 
95th percentile on each of the three pretest evaluation days). However, four participants were 95th percentile on one of the evaluation days.
Ambulatory blood pressure measurements were obtained from the nondominant arm over 24-hour periods pretest and posttest using SpaceLabs Model 90207 monitors (SpaceLabs, Inc., Redmond, WA). The monitors were set to record every 20 minutes during the hours each particpant reported as normal waking hours and every 30 minutes during hours reported as normal sleep hours. These devices have been previously validated (21). The monitors were programmed to repeat a reading if values were outside acceptable ranges of 70 to 285 mm Hg for SBP, 40 to 150 mm Hg for DBP, or 40 to 180 bpm (beats per minute) for HR. Adequacy of readings was based on acceptable readings using previously established criteria (22–24). These included deletion of all readings with error codes and pulse pressure readings (SBP minus DBP) less than 20 mm Hg. Hourly averages were obtained by averaging all readings for each clock hour. Data were reduced by averaging hourly averages into daytime at school (ie, 8 AM to 3 PM), after school (ie, 3 to 10 PM), and nighttime (ie, midnight to 6 AM) levels. Means for ambulatory SBP, DBP, and HR required a minimum of 50% of the total possible observations (ie, 21 daytime or 6 nighttime) to be included in the analysis.
A brief battery of behavioral questionnaires was completed by the participants at both pretest and posttest. The participants completed the Spielberger Anger Expression Scale (anger-in, anger-out, anger control) (25) and the Neighborhood Stress Index (a measure of neighborhood disorder and exposure to violence) (26). Physical activity was measured as self-report of aerobic activity, that is, the number of episodes per week outside of school and in school (eg, physical education class) spent in physical activity sufficient to "work up a sweat." Expectation of benefits was assessed for each treatment (MED vs. CTL) at pretest via brief scales consisting of Likert type responses. All instruments have been validated for use in youth for the age range in the present study (26–30).
Intervention
Two of the four classes were randomly chosen to receive a simple concentrative-type meditation technique that uses the breath as an object of focus and does not require changes in personal or spiritual beliefs. This is a beginner technique taught as Exercise 1 of the MBSR program (31). The rationale for choosing this technique was based on our previous experience with adolescents in implementing a meditation intervention in schools (13). Thus, we elected to implement a meditation program that would be as simple as possible for students to learn and for teachers to implement in a classroom setting. The meditation technique involves having the individual sit upright in a comfortable position with eyes closed. Participants were instructed to focus on the movements of their diaphragm while breathing in a slow, deep, relaxed manner. Participants were taught that if they found their attention shifting toward unrelated thoughts, ideas, or images to simply acknowledge and accept them without making judgments about them and to shift attention back to the breathing. The science teacher (J.B.M.) led the MED practice sessions in the classroom, and these sessions were typically started by dimming the lights at the beginning of the class period. The MED group engaged in 10-minute sessions at school and at home each day for 3 months. In addition to the time that the MED group spent meditating in the teacher’s presence, 20 minutes/week (average of 4 minutes/day) of direct contact time with the instructor was spent discussing issues related to MED sessions (eg, feelings and physical changes during meditation, how to improve meditation experiences, benefits, etc.).
The CTL group was given weekly 20-minute sessions on prevention of high BP and CVD risk factor reduction using National Heart, Lung, and Institute guidelines for youth (20). These included information and instructions on lowering BP through weight loss, diet (reducing fat and sodium intake), and increasing physical activity (ie, daily 20-minute walks after school). Both MED and CTL groups received roughly equivalent amounts of direct contact instruction time from the classroom teacher (20 minutes/week) in addition to 20 minutes/day of meditation for the MED group or 20-minute walks prescribed for the CTL group. The classroom teacher recorded compliance each day with a checklist of participant’s names, marking daily attendance at group meditation sessions and individual meditation practice at home. Data from two individuals who were neither Caucasian nor AA (ie, "other") were excluded to facilitate analysis of ethnicity differences. A third participant who had indicated ethnicity as "other" did not have data at posttest due to equipment failure. The study should be considered as single-blinded, as people assessing and entering the data were unaware of the treatment status of the participants. The participants were instructed not to share information or techniques learned with other individuals.
Statistical Analysis
To check for differences between the two groups at preintervention and/or postintervention on descriptive and anthropometric variables and expectation of benefits scales, a series of analyses of variance (ANOVAs) were performed. Because there were a number of dependent variables, a multivariate analysis of variance (MANOVA) was used to compare changes in groups by treatment. Effects that were significant for the MANOVA were retained, and a series of mixed model univariate analyses were used to determine group differences across the visits for resting and ambulatory daytime (school and after school) and nighttime SBP, DBP and HR and questionnaires including the Neighborhood Stress Index, Anger Expression Scale, and physical activity Likert scales. Results of the univariate analyses are presented as least squares means and standard errors.
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RESULTS |
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Ethnicity and Gender Effects
There were no significant ethnicity and/or gender by treatment by time interactions observed across the 3-month treatment period. Main effects for ethnicity were observed for resting SBP, nighttime SBP, and DBP such that levels for AAs were greater than those for Caucasians (all p values <.03). Levels for Caucasians were greater than for AAs for resting and school HR (both p values <.01). Furthermore, for resting and nighttime DBP, significant differences in change from pretest to posttest were observed by ethnicity, with AAs increasing and Caucasians remaining essentially the same (all p values <.03), but the ethnicity by treatment interactions were not significant (all p values >.05).
Main effects for gender were observed for resting HR, daytime school and home HR, and nighttime HR such that levels for males were lower than for females (all p values <.04). There were no significant gender by time SBP, DBP, or HR differences in change from pretest to posttest for any of the ambulatory measurements or for resting HR. For the resting SBP and DBP, males increased significantly more than females (both p values <.01). The gender by group interactions for BP and HR changes were not significant (all p values >.05).
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DISCUSSION |
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Adult studies have shown that another type of meditation (ie, TM) reduced BP significantly at 3 months in older hypertensive AAs (18,33), normotensive Asian medical students (34) and normotensive Caucasian college students (35). Few BP-related stress reduction studies have been conducted in youth, and findings have been mixed. Relaxation training combined with increased physical activity for four months failed to yield any BP differences in community-home boys compared to a control group (36). A daily progressive muscle relaxation program conducted for 4 months at school in teenagers with high normal BP showed a 5.3 mm Hg greater decrease in their SBP compared with a waiting list control condition (12). Findings in AA adolescents with high normal BP indicated that TM lowered resting SBP/DBP by 7.4/4.7 mm Hg after 2 months of intervention and daytime ambulatory SBP/DBP by 4.3/4.0 mm Hg after 4 months of intervention compared to health education controls (13,19). The present findings at three months compare favorably with and extend the results of the youth studies. That is, using an intent-to-treat analysis, the MED group exhibited a 3.8 mm Hg greater decrease in resting SBP, a 5.6 mm Hg greater decrease in after-school ASBP, and a 5.6 bpm decrease in after-school HR compared to the CTL group. Importantly, in contrast to previous youth studies (12,13,19), participants were not preselected for participation based on high normal BP status.
Main effects for nighttime measures indicated AAs had higher BP compared to Caucasians. This is corroborated by other studies indicating ethnicity differences in BP beginning in childhood (37). Daytime HR was observed to be higher in Caucasians compared to AAs. Not unexpectedly, daytime HR was observed to be higher in females compared to males. The increases observed in daytime (after school) BP in the health education control group may possibly be attributed to self-reported increases in physical activity levels. This is supported by the differential increase in HR observed after school. Both groups reported increased physical activity after school, which might have led to increases in ambulatory BP out of school in both groups, except that meditation might have prevented this increase in SBP in the MED group. This study compares with previous findings involving youth (19) and adults (18) where health education control groups exhibited slight increases in resting BP at follow-up compared with decreases exhibited by TM groups.
The underlying physiological links between stress and BP have not been clearly delineated. Sympathetic nervous system (SNS) and hypothalamic-pituitary-adrenocortical (HPA) axis responses to emotional distress have been posited as contributing to the etiology of EH (38). Even mild irritation without perceived distress may activate the SNS and HPA axis (39). If such activations are frequent or exaggerated, maladaptative changes of long-term BP control mechanisms may occur, leading to EH (40). An assumption underlying studies involving stress reduction techniques is that a decrease in perceived stress occurs that directly influences BP levels. Meditation has been shown to decrease CV reactivity to acute stress (19). Interestingly, participants with low levels of perceived stress assigned to a meditation treatment experienced declines in BP, suggesting that the improvement in BP might not necessarily be due to reduction in perceived stress (33). Further meditation research is needed to examine the relationship between changes in BP and perceived stress levels.
A strength of the study was that BP measures were recorded by ambulatory BP monitors in addition to the use of automated Dinamap BP monitors. Ambulatory BP monitoring has been shown to be a better predictor of hypertension than resting clinic pressure, relatively free of placebo effects, highly reproducible, and sensitive to small changes in average BP (41). This methodology facilitates a large number of measures over 24 hours in the individual’s natural setting (eg, at school and at home) as compared to measures observed in a controlled laboratory environment (19). This approach confers ecological validity to the findings (42).
All participants resided in the same geographical locale, and none participated in any formal lifestyle programs during the intervention period, besides physical education at school. The findings were not attributable to differences in anthropometrics (eg, height, weight, and adiposity), gender, ethnicity, and expectations of health benefits, because the meditation and control groups were similar on these parameters at preintervention. Efforts were made to provide comparable direct contact instruction time at school to both groups (20 minutes/week), with the time devoted to meditation practice (10 minutes twice per day), matching the 20-minute daily walks prescribed for the health education group. In efforts to minimize dilution of the treatment effect, the individuals were instructed not to share meditation or CVD health education techniques with other classes, although it was not possible to control for cross-contamination effects within this design. Future studies may control for this issue by utilizing a different school for each treatment group.
Further studies need to be conducted to determine whether meditation in normotensive youth has lasting impact on BP following completion of formal intervention. Because it is frequently many years before children display overt clinical symptoms of CVD, longitudinal studies are needed to examine the impact of meditation on the development of preclinical manifestations of increased EH risk (eg, increased BP, increased left ventricular mass, decreased arterial elasticity). Future studies should also examine the impact of simple meditation on hypertensive participants and compare its impact to other nonpharmacological BP reduction techniques (eg, physical exercise, meditation techniques, cognitive behavioral programs, etc.) with respect to efficacy (43).
In summary, these findings suggest that in comparison to a health education control group, simple breathing meditation lowered BP and HR in a group of normotensive youth. The meditation technique is easily learned and practiced at no cost (31). It is important to note that the meditation sessions were effectively implemented in the classroom by the teacher. Furthermore, a school-based meditation program was recently shown to not only decrease resting and ambulatory BP (13,19), but also decrease conduct problems and school absences in adolescents (44). Thus, implementation of such programs in the school setting is not only feasible but may also be desirable because of their impact on school-related conduct as well as possible impact on future health.
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ACKNOWLEDGMENTS |
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We would like to thank Dr. Charles Larke, Superintendent of Richmond County Board of Education, as well as the administration, teachers, and students of Tutt Middle School, Augusta, Georgia, for helping to make this study possible.
Received for publication February 12, 2004.
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