Does trait anxiety influence muscle sympathetic nerve activity responsiveness in humans?

Abstract

The relationship between anxiety and muscle sympathetic nerve activity (MSNA) remains equivocal. The purpose of this study was to examine associations between trait anxiety and MSNA in young, healthy adults. We hypothesized that trait anxiety would be positively correlated to resting MSNA and MSNA reactivity to mental stress. Twenty adults (11 men, 9 women; 22±1 years; 24±1 kg/m2) were examined during a 10 min supine baseline and 5 min of mental stress (via mental arithmetic). Psychological measurement included trait anxiety determined using the State‐Trait Anxiety Inventory (STAI), and autonomic measurements included blood pressure (sphygmomanometer and finger plethysomography), heart rate (HR; electrocardiogram), and MSNA (micro neurography). Standardized trait anxiety was 43±2 arbitrary units (range 30 – 57; n=20), while mean baseline values of mean arterial pressure (MAP; n=20), HR (n=20), and MSNA (n=13) were 77±2 mmHg, 68±3 beats/min, and 11±1 bursts/min, respectively. Mental stress significantly (p<0.05) increased MAP (Δ7±1 mmHg; n=20), HR (Δ15±2 beats/min n=20), and MSNA (Δ2±1 burst/min; n=10). Trait anxiety was not correlated with resting MAP (r=−0.053, p=0.824), HR (r=0.193; p=0.415), MSNA burst frequency (r=−0.158; p=0.605), or MSNA burst incidence (r=−0.147; p=0.632). MAP (r=0.311; p=0.182) and HR (r=0.047; p=0.876) reactivity to mental stress were not correlated with trait anxiety. In contrast, trait anxiety was strongly correlated with MSNA reactivity to mental stress quantified as changes (Δ) in MSNA burst frequency (r=−0.742; p=0.014), Δ MSNA burst incidence (r=−0.750; p=0.013), and % change in total MSNA (r=−0.700; p=0.024). Contrary to our initial hypothesis, the associations between trait anxiety and MSNA reactivity to mental stress were negative. In conclusion, this pilot study suggests a negative association between trait anxiety and MSNA reactivity to mental stress. Our findings advocate for the inclusion of basic psychological surveys such as STAI prior to micro neurographic sessions, and we posit that future studies might pool data across various laboratories to more definitively determine the role of psychological states and traits on sympathetic neural activity and reactivity in humans.Support or Funding InformationSupport from NIH (HL‐122919).