10-Week Hatha Yoga Increases Right Hippocampal Density Compared to Active and Passive Control Groups: A Controlled Structural cMRI Study

Abstract

Background:The current study was designed to evaluate potential Yoga specific changes of brain structure in comparison with an active sport group and a passive control group. Materials and Methods:We conducted a longitudinal structural MRI study to investigate changes in gray matter (GM) density following a Yoga intervention. In order to check the repeatability of the results two data acquisition periods (cohorts) with the same study design were done. Yoga naive subjects (n = 19/n = 20) received a Yoga intervention once a week for 75 minutes over a period of 10 weeks. Control groups included active sport subjects (n = 10/n = 22) and passive subjects (n = 17/n = 14). All participants could choose their group assignment by their own preference. A longitudinal and group comparison was done by voxelbased-morphometric analyses before and after the intervention. In addition, blood pressure was taken before and after the study period as a controlling instrument. Finally, the results of the two cohorts were reported into a comprising data set for a general conclusion on Yoga effects. Results:Initially, hippocampal GM density in the Yoga group was significantly lower than in both control groups already before the intervention. It was equally and independently present in both cohorts. The longitudinal MRI measurements showed a significant increase in the right hippocampal GM density as a specific effect of the Hatha Yoga intervention. Coincidentally, the blood pressure measurement detected a significant reduction in both systolic and diastolic blood pressure in the Yoga group but not in the sport or passive group. Conclusions:Various neurodegenerative and neuropsychiatric diseases as well as long lasting stress lead to structural shrinkage of the hippocampal GM. In contrast, stress reduction was shown to be associated with an increase in the hippocampal GM density. The Yoga specific effect in this study can be considered as positive impact on both stress management and its underlying neural structure. These effects have been already proven in prevention and therapy of neurodegenerative and neuropsychiatric diseases. The Yoga-induced stress reduction can be furthermore supported by the findings of blood pressure reduction. Blood pressure is well known as an indirect indicator for stress reduction. Since the GM density was detected lower in the two Yoga cohorts twice compared to both control groups, one may postulate a pre-existing but unconscious higher stress vulnerability when voluntarily deciding for the Yoga intervention.

Yoga Effects on Brain Health: A Systematic Review of the Current Literature

“…Garner and colleagues [29] investigated the impact of yoga training on GM density, which is related to a voxel's signal intensity and is reflective of the amount of gray matter within each voxel. They did this by comparing changes in GM density among healthy young adults after a 10-week intervention in which participants self-selected enrollment in a Hatha yoga, sport control, or passive control group.…”

Effects of Mind–Body Exercise on Brain Structure and Function: A Systematic Review on MRI Studies

“…Both the 12-week TCC and BDJ interventions increased the GMV in the hippocampus/MTL, and the increased GMV was positively associated with improved memory abilities [ 55 ]. Increased hippocampal GMV (compared with controls) and GMD (compared with active sport and passive groups) were reported in two yoga intervention groups, respectively [ 48 , 59 ].…”

“…Both cross-sectional and intervention studies reported the effect of mind–body exercise on structural changes in the hippocampus/MTL [ 32 , 43 , 48 , 55 , 59 ]. Notably, the positive changes in the hippocampus/MTL structure were related to the improvement in the cognitive function, particularly the memory function [ 32 , 55 ].…”

“…The effects of mind–body exercises on the hippocampus are similar to the findings of physical activity [ 64 ] and mindfulness meditation [ 65 ], suggesting that physical activity alone or meditation alone, as well as the combination of both, improves the brain structure related to memory. In addition, the intervention study [ 59 ] conducted by Garner et al indicated that yoga experts have a significantly increased GMD in the hippocampus compared with a sport group (stretching and strengthening training), implying that mind–body exercises are more effective in improving the hippocampal structure than physical exercises alone. However, because of the methodological defects of the study (participants were not randomly allocated), the baseline hippocampal GMD in the yoga group was significantly lower than in the sport group.…”

The Individual Inclination to an Occupation and its Neuronal Correlate

“…In longitudinal studies, the effect of training on a single group of subjects is examined according to defined time intervals. It can be observed that training leads to an intra-individual shift toward an increase in Gray matter at the cost of a decrease in the relative extent of White matter in the corresponding brain regions (Draganski et al, 2006;Krick et al, 2015;Garner et al, 2019). Those structural shifts usually were correlated to gradually measured performance scores.…”