Table 5 

Significant correlations with r absolute value ≥ 0.05 between symptom scales and HRV parameters evaluated during sleeping hours (0000 to 0600 hours). 

Fibromyalgia (n = 22) 
Control (n = 22) 



r 
P value 
r 
P value 



FIQ total score 
SDNN 
0.69 
< 0.001 

SDANN 
0.60 
0.003 

FIQ VAS pain 
SDSD 
0.65 
0.001 

RMSSD 
0.65 
0.001 

pNN50 
0.62 
0.002 

FIQ VAS fatigue 
SDNN 
0.65 
0.001 

SDANN 
0.57 
0.005 

FIQ VAS anxiety 
SDNN 
0.62 
0.002 

SDANN 
0.53 
0.011 

FIQ VAS depression 
SDNN 
0.52 
0.012 

SDANN 
0.51 
0.015 

COMPASS constipation 
SDNN 
0.53 
0.010 

HADS depression 
Mean NN 
0.53 
0.010 

SF36 mental component 
SDSD 
0.64 
0.001 

RMSSD pNN50 
0.64 0.64 
0.001 0.001 



COMPASS, composite autonomic symptom scale; HADS, hospital anxiety and depression scale; FIQ, fibromyalgia impact questionnaire; Mean NN, mean NN interval; pNN50, percentage of adjacent pairs of RR intervals that differ by more than 50 ms from each other in a given time period; RMSSD, square root of the mean of the squares of differences between adjacent NN intervals; SDANN, mean standard deviation of the average NN intervals calculated over 5 minutes; SDNN, standard deviation of the NN intervals; SDSD, standard deviation of the successive NN differences; SF36, health survey short format 36 items; VAS, visual analogue scale. 

Lerma et al. Arthritis Research & Therapy 2011 13:R185 doi:10.1186/ar3513 