Effectiveness of fixed-site high-frequency transcutaneous electrical nerve stimulation in chronic pain: a large-scale, observational study

Figures & data

Figure 1 Schematic illustration of timing of pain ratings and therapy for subjects included in the study cohort.

Table 1 Demographics and pain characteristics of study cohort

Characteristic	All (N=713)	Utilization subgroups			P-value
		Low (n=148)	Intermediate (n=327)	High (n=238)
Female, n (%)	373 (52.3)	74 (50.0)	179 (54.7)	120 (50.4)	0.3663
Age (years), mean (SD)	55.4 (13.7)	55.0 (14.7)	55.2 (13.8)	55.9 (13.1)	0.8028
BMI (kg/m^2), mean (SD)	30.3 (7.0)	31.9 (8.0)	30.2 (7.1)	29.7 (6.2)	0.0305
Duration of pain >3 years, n (%)	527 (73.9)	103 (69.6)	236 (72.2)	188 (79.0)	0.0061
Daily pain, n (%)	691 (96.9)	143 (96.6)	311 (95.1)	237 (99.6)	0.0096
Number of pain sites, mean (SD)	4.8 (2.5)	4.8 (2.5)	4.8 (2.5)	4.9 (2.6)	0.7191
Number of painful health conditions, mean (SD)	3.6 (2.2)	3.7 (2.4)	3.6 (2.3)	3.7 (2.2)	0.8998
Baseline pain, mean (SD)
Average pain	6.23 (1.95)	6.28 (2.02)	6.22 (1.95)	6.21 (1.91)	0.9491
Sleep interference	5.23 (2.94)	5.84 (2.84)	5.03 (3.01)	5.11 (2.87)	0.0151
Activity interference	6.61 (2.43)	6.93 (2.50)	6.60 (2.43)	6.43 (2.35)	0.1458
Mood interference	6.29 (2.63)	6.46 (2.67)	6.20 (2.67)	6.30 (2.55)	0.6039

Notes: Low, therapy on ≤30 days. Intermediate, therapy on 31–56 days. High, therapy on ≥57 days. P-value is for one-way ANOVA among the three utilization subgroups.

Abbreviation: SD, standard deviation.

Table 2 Self-reported painful health conditions

Condition, n (%)	N=713
Musculoskeletal
Arthritis	444 (62.3)
Fibromyalgia	182 (25.5)
Spinal
Herniated disc	217 (30.4)
Spinal stenosis	205 (28.8)
Neuropathic
Diabetes	93 (13.0)
Complex regional pain syndrome	168 (23.6)
Shingles/post herpetic neuralgia	31 (4.3)
Restless leg syndrome	143 (20.1)
Multiple sclerosis	20 (2.8)
Previous injury
Back	290 (40.7)
Neck	160 (22.4)
Arm/hand	155 (21.7)
Leg/foot	13 (1.8)
Cancer	41 (5.8)
Headaches/migraine	176 (24.7)
Others	254 (35.6)

Note: More than one category per participant may apply.

Table 3 Anatomical distribution of pain

Location, n (%)	N=713
Lower extremity	641 (89.9)
Feet/ankle	360 (50.5)
Leg (including knees)	535 (75.0)
Hips	412 (57.8)
Low back	575 (80.6)
Trunk (midsection)	164 (23.0)
Upper extremity	478 (67.0)
Hands/wrist	309 (43.3)
Arms	177 (24.8)
Shoulders	375 (52.6)
Neck	359 (50.4)
Head/face	117 (16.4)
Others	72 (10.1)

Note: More than one category per participant may apply.

Table 4 FS-TENS therapy over 60-day assessment period

Parameter, mean (SD)	All (N=713)	Utilization			P-value
		Low (n=148)	Intermediate (n=327)	High (n=238)
Number of days with ≥1 session	44.5 (16.1)	18.4 (8.1)	45.2 (7.4)	59.7 (1.4)	0.0000
Number of nights with ≥1 session	19.6 (19.2)	5.4 (6.3)	16.2 (14.8)	33.1 (21.4)	0.0000
Sessions/day	6.3 (2.6)	4.5 (2.0)	5.8 (1.9)	8.1 (2.7)	0.0000
Total number of sessions	301 (192)	88 (58)	264 (109)	485 (168)	0.0000
Mean stimulation level (mA)	27.1 (14.0)	25.9 (12.9)	27.2 (14.0)	27.4 (14.6)	0.5840

Notes: Low, therapy on ≤30 days. Intermediate, therapy on 31–56 days. High, therapy on ≥57 days. P-value is for one-way ANOVA among the three utilization subgroups. Session, 1 hour continuous stimulation.

Abbreviations: FS-TENS, fixed-site high-frequency transcutaneous electrical nerve stimulation; SD, standard deviation.

Table 5 Changes in pain measures from baseline to 60-day follow-up in FS-TENS users

Pain measure, mean (SD)	All (N=713)	Utilization			P-value
		Low (n=148)	Intermediate (n=327)	High (n=238)
Average pain	−0.37 (2.51)*	0.23 (2.60)	−0.31 (2.38)*	−0.82 (2.54)*	0.0003
Sleep interference	−0.31 (3.07)*	0.03 (3.18)	−0.22 (2.97)	−0.65 (3.13)*	0.0814
Activity interference	−0.99 (2.69)*	−0.51 (2.70)*	−0.94 (2.63)*	−1.36 (2.74)*	0.0019
Mood interference	−1.02 (2.78)*	−0.22 (2.73)	−0.97 (2.66)*	−1.58 (2.87)*	0.0000
Follow-up (days)	58.78 (5.62)	58.97 (7.18)	58.20 (5.74)	59.47 (4.06)	0.0267

Notes: Low, therapy on ≤30 days. Intermediate, therapy on 31–56 days. High, therapy on ≥57 days. P-value is for one-way ANOVA among the three utilization subgroups.

* Statistical significance of baseline to 60-day follow-up changes determined by Wilcoxon rank sum test, P<0.05.

Abbreviations: FS-TENS, fixed-site high-frequency transcutaneous electrical nerve stimulation; SD, standard deviation.