Impact of Transcendental Meditation® on cardiovascular function at rest and during acute stress in adolescents with high normal blood pressure
Introduction
Essential hypertension (EH) remains a significant health problem in the US with approximately 40 to 50 million persons affected [1]. Epidemiological studies have shown that blood pressure (BP) percentile ranking relative to age mates tends to track from late childhood through adolescence into adulthood [2], [3]. Teenagers with high normal BP are at increased risk for development of EH as young adults [4], [5], [6], [7]. From late childhood onward, African Americans (AAs) exhibit higher casual BP than Caucasian Americans (CAs) [8]. Thus, AA youth with high normal BP are at particular risk for EH [8], [9].
Although the relationship between cardiovascular reactivity (CVR) and EH has been controversial, exaggerated CVR to stress has been hypothesized as contributing to the early etiology of EH [10], [11], [12]. Exaggerated CVR to laboratory stressors has been shown to predict future EH in adults [13], [14], [15], and change in BP levels and left ventricular mass 1 to 6 years later in youth [16], [17], [18], [19], [20], [21]. It has been hypothesized that the high prevalence of EH among AAs is in part due to their greater exposure to chronic environmental stress related to sociostructural barriers (e.g., racism, inadequate economic resources) [11], [22], [23], [24]. Similar to adult findings [22], [25], [26], [27], AA youth often exhibit greater BP reactivity to stress than CA youth, and the underlying hemodynamic mechanism frequently responsible is increased total peripheral resistance (TPR) [17], [28], [29], [30].
Few studies have examined whether stress reduction methods reduce casual BP in youth with high normal BP, and the results of those studies are mixed. Ewart et al. [31] examined the efficacy of progressive muscle relaxation (PMR) training in teenagers with BP above the 85th percentile. PMR instruction provided in class for 3 months reduced the systolic blood pressure (SBP) compared to a waiting-list control condition, but group BP differences 4 months later were not significant [31]. In another study, relaxation training combined with increased physical activity did not decrease BP compared to a control group in community-home boys [32].
Recent research suggests that behavioral stress reduction via Transcendental Meditation (TM) may hold promise in the reduction of casual BP and/or CVR in at-risk youth. Recent clinical trials found that TM lowered clinic BP, and reduced the risk of heart disease, carotid atherosclerosis, and mortality in hypertensive AA adults [33], [34], [35], [36], [37]. Further, a recent finding with long-term TM practitioners indicated that acute declines in BP during TM are due to decreases in TPR [38]. Goleman and Schwartz [39] found that TM reduced heart rate (HR) reactivity to a stressful film in normotensive CA adults, but another study of normotensive CA adults found no decreases in HR or BP reactivity to three laboratory stressors [40]. TM has also been shown to effect beneficial stress-related physiological changes, including decreased sympathetic nervous system arousal [41], [42], hypothalamic–pituitary–adrenocortical axis dysregulation [43], [44], cortisol levels [44], and sympathetic β-adrenergic receptor sensitivity [45]. These findings suggest that examination of the effects of TM on reducing BP and CVR in at-risk youth is warranted.
In the present study, youth with high normal BP, primarily AAs, were randomly assigned to either a 2-month TM program or a health education control (CTL) group. Based on previous findings, it was predicted that youth who practiced TM would exhibit greater decreases in resting BP and TPR, and greater decreases in CVR to laboratory stressors from pretest to 2-month posttest than controls.
Section snippets
Participants
Permission to conduct the study was granted by the Superintendent of Richmond County Public Schools and the Medical College of Georgia Human Assurance Committee. A BP screening was conducted on a random sample of youth at an inner-city high school (200 students, 97% AAs). Thirty-five adolescents (34 AAs, 1 CA; ages 15–18 years) exhibited resting SBP in the sitting position in the ≥85th and ≤95th percentile for their age and gender on three consecutive occasions [46]. Exclusion criteria
Descriptive characteristics
The average attendance of the TM and CTL groups at the school sessions was 67.8% and 68.2%, respectively. The average self-reported compliance with TM practice at home was 76.6%. The percentage of students attending at least 60% of the total possible sessions was 80% for the TM groups and 58% for the CTL group. Descriptive characteristics of the TM and CTL groups are presented in Table 1, Table 2. There were no significant main (i.e., intervention, time) or interaction effects for any parameter
Discussion
This study examined the impact of a 2-month participation in the TM technique on CV function at rest and during acute stress in adolescents with high normal BP. With respect to resting CV function, the TM group exhibited greater decreases in resting SBP and a trend for greater decreases in DBP compared to the control group. These findings were not attributable to differences in anthropometrics or demographics since the TM and control groups were similar on these parameters at pre- and
Acknowledgements
We would like to thank Dr. Charles Larke, Superintendent; Dr. Rush Utley and Mr. Quentin Motley, Principals, Richmond County Public Schools in Augusta, GA for their cooperation in providing the facilities for this study. This study was supported in part by National Institutes of Health Grant #HL62976 to Dr. Treiber and an American Heart Association Scientist Development Grant #9930073N to Dr. Barnes.
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