Table 1 Study selection criteria

Participants

Healthy, adult long-term meditators (LTMs) practicing any type of meditation technique denoted by the umbrella term “meditation.”

(A long-term meditator was defined as a meditator with a mean practice experience of at least 3 years or more in a particular type of meditation, regardless of the daily routine practice and retreat experience for the purpose of selecting studies to be included in this review)

Studies involving unhealthy/diseased individuals, monks as “LTMs”, and those younger than 16 years and/or older than 70 years were excluded

Study design

Controlled trials and observational studies (cross-sectional, longitudinal, case–control, and cohort)

Articles not available in full-text form, reviews, case reports, news items, conference proceedings, and unpublished data were excluded

Intervention and comparison

Studies involving LTMs in any type of meditation technique, comparing selected respiratory function parameters at rest in healthy LTMs with matched controls, short-term meditators (STMs) or both, and/or studies comparing selected respiratory function parameters of LTMs during meditation with the same respiratory function parameters at rest, and studies which assessed the associations between selected respiratory function parameters and meditation practice variables were considered as eligible to be included in this review

Studies involving non-meditative relaxation techniques

Outcome

Studies investigated on selected respiratory function measures of healthy LTMs at rest and during meditation including rate of respiration (RR), spirometry parameters (forced expiratory volume in the first second (FEV₁), ratio of forced expiratory volume in the first second/forced vital capacity (FEV₁/FVC), peak expiratory flow rate (PEFR), tidal volume (TV), vital capacity (VC), and minute ventilation

Reports in which the practice experience of LTMs was unclear were not included