Fig. 2

Correlation of age, blood pressure and BMI with the reactive hyperaemia index (RHI). Correlations of the RHI with age (a–c), systolic blood pressure (d–f), diastolic blood pressure (g–i) and BMI (j, k) for ME/CFS patients (n = 14; a, d, g, j), PCS patients (n = 16; b, e, h, k) and healthy controls (HC) (n = 15; c, f, i). Correlation analysis was performed using the nonparametric Spearman coefficient. A two-tailed p value ≤ 0.05 was considered statistically significant