Normative data for the 10-min Lean Test in individuals without Orthostatic Intolerance

Background

Orthostatic intolerance syndromes such as Orthostatic Hypotension (OH) and Postural Orthostatic Tachycardia Syndrome (PoTS) are common symptoms seen in post-infection conditions and other neurological conditions with autonomic dysfunction. The 10-minute National Aeronautics and Space Administration Lean Test (NLT) is an objective clinical test used to assess these symptoms and direct management. There is, however, no robust literature on normative data for this test, particularly from a younger population.

Aims

The aim of this study was to produce a healthy control data set for NLT, which can be used for comparison with the patient population with health conditions.

Methods

Individuals recruited into the study had no history or symptoms of orthostatic intolerance; autonomic dysfunction; post-infection conditions (such as long COVID); or other neurological conditions with hemodynamic instability. Participants were primarily recruited from the general population in a metropolitan city. All participants underwent a standardised NLT. Lying Blood Pressure (BP) and Heart Rate (HR) after 2 min of lying down supine was recorded, followed by BP and HR recordings at every minute of standing (leaning against a wall) up to 10 minutes, along with recording patient-reported symptoms at each time point.

Results

A complete dataset was available for 112 individuals (60.7% Female, 39.3% Male). The population was 61.6% Caucasian, 8.0% Asian, 3.6% Black/Caribbean, 9.8% Mixed, and 17.0% Other; the mean age was 35.3 ± 15.1, with a BMI of 24.8 ± 4.0; 30.6% of individuals had a background medical condition, but none of the exclusion criteria.

During NLT, upon standing, the average change of HR was an increase of 9.89 ± 8.15bpm. The sustained HR increase (HR increase sustained at two consecutive readings) was an average of 6.23 ± 6.94bpm. The predominant response with BP was an increase of systolic BP, with the average initial increase being 7.55 ± 10.88mmHg. None of the participants met the diagnostic criteria for symptomatic OH or PoTS during NLT.

Conclusion

For the first time in the current literature, NLT data from a relatively younger healthy population without orthostatic intolerance have been gathered. This normative data will help interpret NLT findings in younger patients with Orthostatic Intolerance better and be useful in managing dysautonomia in specific conditions.