Effect of Self-Reported Anxiety Levels on Blood Pressure Responses to Slow Breathing.

Anxiety, an emotion involved in the development and presentation of anxiety disorders, is linked to elevated blood pressure (BP) which may contribute to the increased cardiovascular disease risk observed in individuals diagnosed with anxiety disorders. Slow breathing (SB), defined as a respiration rate below 10bpm, has been implemented successfully to reduce BP in several clinical populations. However, to the best of our knowledge, the efficacy of SB has yet to be investigated in individuals with anxiety. Therefore, the purpose of this study was to compare BP responses to an acute bout of SB between individuals with moderate to severe anxiety and individuals with no or mild levels of anxiety. We hypothesized that individuals with moderate/severe anxiety levels would exhibit greater SB-induced decreases in BP compared to individuals with no/mild anxiety levels. We assessed 14 young (18-25 years old) lean (body mass index < 24.9kg/m ) non-smoking individuals with moderate/severe anxiety levels (n=7), as well as age- and body mass index-matched individuals with no/mild anxiety levels during 15-mins of rest and during 15-mins of device-guided SB (RESPeRATE). Anxiety levels were assessed using the Hospital Anxiety and Depression Scale, in which participants with a score of at least 8 were categorized as having a moderate/severe anxiety score (ANX) and individuals with scores less than 8 were classified as having no/mild anxiety levels (CTRL). Respiratory patterns were monitored via respitrace strain gauge. Beat-by-beat BP was measured using finger photoplethysmography calibrated to values obtained from manual sphygmomanometry. Respiratory and systolic BP (SBP) data were extracted averaged across 5-mins of steady state rest and during the final 5-mins of SB; differences between ANX and CTRL were evaluated using unpaired t-tests. Despite similar resting SBP between ANX and CTRL (111.28 ± 11.40 vs 109.39 ± 7.05mmHg; p=0.75), the SBP response to SB differed between ANX and CTRL (-2.18 ± 4.84 vs 3.57 ± 4.47mmHg; p=0.04). In fact, ANX experienced a clinically meaningful SB-induced reduction in BP (defined as a change greater than or equal to 2 mmHg) that was absent in CTRL. Interestingly, resting respiration rates were higher in ANX than CTRL (13.33 ± 4.07 vs 7.74 ± 2.18bpm; p<0.01), and reductions in respiration rate during SB were greater in ANX than CTRL (-9.27 ± 3.74 vs -2.66 ± 2.19bpm; p<0.01). Taken together, in a young and relatively healthy cohort of individuals with a range of self-reported anxiety levels, it appears that SB is effective in lowering SBP in individuals with moderate or high levels of anxiety but has no effect in individuals reporting no or low levels of anxiety. Thus, SB may be an effective intervention to reduce BP in individuals with high anxiety levels, which may have long-term implications in the treatment of elevated BP and reduction of cardiovascular disease risk in individuals diagnosed with anxiety disorders.