- Heart rate: Studies consistently show that the heart rate slows during meditation anywhere from 2 or 3 to 15 beats per minute, with greater declines for advanced meditators. At the same time (and possibly the reason for the decrease), cardiac output increases by as much as 15 percent.
- Blood pressure: One of the most frequently studied parameters, blood pressure consistently decreased in a score of studies by as much as 25 mmHg systolic (among normal and moderately hypertensive subjects).
- Brainwaves: Meditators experience more alpha rhythms, both during and between practice sessions. Advanced meditators also have brief bouts of theta, during which they report feeling peaceful, spacious, and self-aware.
- Dehabituation: Whereas Zen meditators experience sounds freshly no matter how often they occur, yogic meditators (who are taught to withdraw their senses rather than heighten their awareness) habituate to sounds and gradually become less responsive.
- Stress chemicals: As one might expect from a practice renowned for reducing stress, meditation brings down the levels of cortisol (the primary stress hormone produced by the adrenals) by as much as 25 percent in advanced practitioners and lactate (a chemical released into the bloodstream during stress) by as much as 33 percent.
- Cholesterol: Regular practice of meditation reduces serum cholesterol levels as much as 30 mg/dL.
- Metabolism: Dozens of studies have found that meditation reduces oxygen consumption by as much as 55 percent, CO2 elimination by up to 50 percent, and breathing rate from a norm of 14 to 16 breaths per minute to as few as 1 or 2.
- Longevity: Long-term studies of TM practitioners show they live on average nearly 8 years longer than their nonmeditating counterparts, with 30 percent fewer cardiac fatalities and 50 percent fewer deaths from cancer.
- Medical-care utilization: An 11-year study of TM practitioners found they logged 74 percent fewer hospital days, 55 percent fewer outpatient visits, and 63 percent fewer total medical expenses than subjects in a nonmeditating control group.
