Highly variable breathing rate, regardless of sleep quality, is a marker of neuropsychophysiological stress

Introduction Differences in breathing patterns, even with similar sleep quality, may reflect a neurophysiological state indicating the importance of attention to the breath. Breathing rate variability (BRV) is known to be higher during psychophysically stressed states and is often associated with high BMI, high blood pressure (BP), higher attention-anxiety-aggression problems. It is also known that spontaneous neuronal activity estimated with fractional amplitude of low-frequency fluctuations (fALFF) is higher in the occipital cortex, correlated with sleep deprivation; and fALFF is lower in the frontoparietal cortex associated with poor attention/emotion control. Thus, we predicted that BRV would correlate with fALFF and the fALFF activity would be worse in a group with higher BRV.Methods: In this study, we estimated fALFF during rest in groups showing deep breath [(n=21, 5 males) age 29±4 years, BMI 26±5 kg/m2] vs. a serial, rhythmic set of tapers in breathing (burst) [(n=21, 14 males) 30±4 years, 28±6 kg/m2]. Pittsburgh Sleep Quality Index (PSQI), Blood Pressure (BP), Adult Self Report (ASR) raw scores for anxiety-attention-aggression problems as found in the HCP data are reported for the burst and deep-breath groups. BRV was estimated in the two groups from respiration belt data at 15 minutes of rest. fALFF was calculated from resting-state fMRI data. Then, BRV was correlated with fALFF, followed by group differences in fALFF with BRV as a co-variate. Results: Burst group showed higher BRV (4±3 breaths per minute or bpm) compared to the deep-breath group (3±3 bpm). PSQI in both groups was 5±3. Systolic BP in the burst group was higher by 7 mmHg. ASR raw scores showed higher (by 2 points) anxiety-attention-aggression problems in the burst group. Only in the burst group, BRV positively correlated with BMI (r = 0.5, p<0.05). fALFF correlated with BRV in both groups in cerebrospinal fluid (CSF) areas (strongest in lateral ventricles), p<0.05 corrected for multiple comparisons. With BRV as co-variate, the burst group showed higher fALFF activity compared to the deep-breath at the visual and somatosensory regions, p<0.05 corrected for multiple comparisons.Discussion: Although PSQI scores in both groups did not differ, the burst compared to the deep breath group showed higher stress in terms of psychophysiological variables. BRV correlated with fALFF. Keeping BRV as co-variate, higher fALFF was observed in burst compared to deep breath group at the visual and somatosensory regions, a finding common in the sleep-deprived population. Overall, our results indicate that irrespective of sleep quality, individuals showing the tendency to take deep breaths during resting state have improved neuropsychophysiological states.