A claim you hear on longevity podcasts
The claim checked: A longer out-breath than in-breath switches off the stress system Hear it at 10:19
One trial found the breath ratio made no difference to stress in healthy adults; four found mixed effects, two of them in veterans with PTSD.
Computed from 5 studies that test this point, each judged by two readers, in full. 10 more studies are waiting for a full read and do not count yet.
“now with breath work one of the key principles to think about is when your out breath is longer than your in breath you have to switch off the stress part of your nervous system and promote the relaxation part”
None.
other primary study · 2014
“Contrary to what one would expect, heart rate was increased when breathing at a low i/e ratio as compared to a high i/e ratio.”
Inhalation/Exhalation ratio modulates the effect of slow breathing on heart rate variability and relaxation. Appl Psychophysiol Biofeedback
Who: undergraduate students aged 18-22 (30 recruited, 2 men; 23 analysed) without cardiac, respiratory or psychiatric disorders
PMID 25156003
controlled trial · 2023
“No significant changes were found in heart rate variability or resting heart rate over the course of the study in either of the groups ( Figures 4 C and 4D).”
Brief structured respiration practices enhance mood and reduce physiological arousal. Cell Rep Med
Who: 108 healthy adults 18+ (mostly Stanford undergraduates) randomized remotely to cyclic sighing, box breathing, cyclic hyperventilation with retention, or mindfulness meditation
PMID 36630953
controlled trial · 2018
“DGB acutely lowers BP and MSNA and improves sympathetic but not cardiovagal BRS in prehypertensive veterans with PTSD.”
Acute effects of device-guided slow breathing on sympathetic nerve activity and baroreflex sensitivity in posttraumatic stress disorder. Am J Physiol Heart Circ Physiol
Who: 23 post-9/11 prehypertensive veterans with combat-related PTSD, mostly African-American men
PMID 29652544
controlled trial · 2020
“In summary, 8 wk of DGB lowered sympathetic reactivity to mental stress in PTSD without changes in BP reactivity or resting MSNA, BP, HR or BRS.”
Eight weeks of device-guided slow breathing decreases sympathetic nervous reactivity to stress in posttraumatic stress disorder. Am J Physiol Regul Integr Comp Physiol
Who: Post-9/11 veterans with combat PTSD and prehypertensive blood pressure, mostly African-American men
PMID 32847397
controlled trial · 2023
“In our analyses for group differences, breath ratios do not have a significant effect on psychological and physiological stress measures among healthy adults.”
Slow breathing for reducing stress: The effect of extending exhale. Complement Ther Med
Who: 99 healthy adults aged 30-60 (mean 41, 79% female) with PROMIS Anxiety score of 45 or higher, non-smokers without pulmonary disease, Vanderbilt University Medical Center
PMID 36871835
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