Abstract
Background
Chronic neck pain (CNP) is a common musculoskeletal disorder and a major contributor to disability. Although acupuncture is beneficial for CNP, evidence on the optimal treatment frequency, particularly in young adults, remains limited.
Objective
To compare the clinical efficacy of different electroacupuncture treatment frequencies in young adults with CNP.
Methods
In this single-center, three-arm randomized controlled trial, 90 young adults with CNP were randomized 1:1:1 to three sessions per week (TSWA), one session per week (OSWA), or a waiting-list control (WL). Both acupuncture groups received bilateral electroacupuncture at Jingbailao (EX-HN15) and Jianzhongshu (SI15) for 30 min per session for 4 weeks. Participants and the treating acupuncturist were not blinded; outcome assessors and statisticians were blinded. The primary outcome was the Northwick Park Questionnaire (NPQ). Secondary outcomes were VAS, SF-MPQ, PPT, and PTO. Analyses followed the intention-to-treat principle with multiple imputation.
Results
All 90 randomized participants were included in the analysis. Significant group-by-time interactions were observed for all outcomes (all P < 0.001). At week 4, both acupuncture groups were superior to WL. TSWA was also superior to OSWA for NPQ (P = 0.0196), VAS (P = 0.0042), SF-MPQ (P = 0.0200), and PTO (P = 0.0038), but not PPT (P = 0.0869). At 4-week follow-up, TSWA remained superior to OSWA only for VAS (P = 0.007); NPQ and SF-MPQ no longer differed significantly between groups.
Conclusion
Both treatment frequencies improved pain, functional disability, and selected pain-threshold outcomes compared with WL. Three sessions per week produced greater short-term benefit, but its longer-term advantage was limited and was retained only for VAS at follow-up.
Trial Registration
International Traditional Medicine Clinical Trial Registry, ITMCTR2025001658.
Keywords: chronic neck pain, acupuncture frequency, electroacupuncture, randomized controlled trial, young adults
Introduction
Chronic neck pain (CNP) is one of the most common musculoskeletal disorders, characterized primarily by persistent or recurrent pain in the neck and shoulder region accompanied by functional limitation, and it is also a major contributor to the global burden of disability. Epidemiological studies have shown that approximately 203 million people worldwide were affected by neck pain in 2020, with an age-standardized prevalence of about 2,450 cases per 100,000 population, and the total number of affected individuals is projected to continue increasing through 2050.1 Particularly among young adults, CNP not only leads to persistent pain and neck-related dysfunction, but is also associated with poor sleep quality,2 psychological distress such as anxiety and depression,3 reduced life satisfaction and overall quality of life,4,5 as well as adverse outcomes including impaired academic participation and social functioning.6 Therefore, it warrants greater clinical attention.
At present, the management of CNP is primarily based on conservative treatment. As an important non-pharmacological intervention, acupuncture has been supported by a substantial body of clinical research because of its favorable clinical efficacy, relative safety, good reproducibility, and high patient acceptability, and it has gradually become an important component of comprehensive management for CNP.7−10 However, the therapeutic effect of acupuncture does not depend solely on acupoint selection itself, but may also be influenced by multiple intervention-related parameters. Existing studies generally suggest that acupuncture exhibits certain dose–effect characteristics, with its stimulation dose being jointly regulated by multiple operational and treatment parameters, including needle insertion depth, stimulation technique and intensity, needle retention time, as well as the number and frequency of treatment sessions.11−13 Among these, treatment frequency, as an important component of the overall stimulation dose, may influence both clinical efficacy and the maintenance of therapeutic effects through its interaction with other parameters.14
Available evidence also suggests that treatment frequency itself may alter the speed and magnitude of acupuncture benefit. A recent randomized trial in CNP used bilateral Jingbailao (EX-HN15) and Jianzhongshu (SI15) with a twice-weekly electroacupuncture schedule,10 while a scoping review found that frequency-effect relationships vary by condition and may be nonlinear.14 We therefore compared three sessions per week with one session per week to contrast an intensified schedule with a lower-burden schedule around a clinically used twice-weekly regimen, while keeping the acupoint prescription and stimulation parameters constant. Jingbailao and Jianzhongshu were selected because this standardized local point prescription has been used in previous CNP electroacupuncture research.10
Although the effectiveness of acupuncture for CNP has been supported by relatively substantial evidence, evidence regarding the optimization of different acupuncture treatment frequencies, especially in young adults with CNP, remains limited. Accordingly, this randomized controlled study divided young adults with CNP into 3 sessions per week of acupuncture(TSWA), 1 session per week of acupuncture (OSWA) and a waiting-list (WL) group, to compare the effects of different treatment frequencies on outcome measures including pain, functional impairment, and pain thresholds, and to further evaluate short-term efficacy as well as changes in therapeutic effects during follow-up. This study is expected to provide clinical evidence for optimizing acupuncture treatment frequency in young adults with CNP and to offer a reference for the standardization and evidence-based development of acupuncture treatment protocols.
Methods
Design
This study was a single-center, three-arm, randomized controlled clinical trial designed to compare the clinical efficacy of different frequencies of electroacupuncture (EA) in young adults with CNP. The study was conducted in accordance with the principles of the Declaration of Helsinki and was approved by the Ethics Committee of Guangdong Provincial Hospital of Chinese Medicine (No. YF2025-099-01). Written informed consent was obtained from all participants before enrollment. The study was registered with the International Traditional Medicine Clinical Trial Registry (ITMCTR2025001658).
Participants
A total of 90 young adults with CNP were enrolled from the outpatient clinics of the Department of Acupuncture and Moxibustion and the Traditional Therapy Department, Guangdong Provincial Hospital of Chinese Medicine, between September 2025 and March 2026.
The diagnosis of CNP was based on the criteria proposed by the Orthopedics Section of the American Physical Therapy Association (APTA).7,15,16 Participants were eligible for inclusion if they met all of the following criteria: aged 18–44 years; neck pain as the chief complaint, or restricted cervical motion accompanied by neck pain or discomfort; a Visual Analogue Scale (VAS) score of at least 3, with symptoms present on at least 5 days during a consecutive 1-week period; symptom duration of at least 3 months; and no acupuncture, massage, or other related treatments within the previous month.
Participants were excluded if they met any of the following criteria: a history of cervical fracture or cervical spine surgery; congenital deformity, local skin lesions, or bleeding disorders in the neck region; other severe primary diseases that were poorly controlled; cognitive impairment preventing comprehension of the study procedures or completion of the relevant questionnaires; pregnancy, lactation, or plans to become pregnant within the next 6 months; or concurrent participation in another clinical trial.
Medication history was collected as part of the baseline clinical information. Participants were not permitted to use analgesic medications for neck pain during the study period.
Randomization and Blinding
Eligible patients were randomly assigned to 1 of 3 groups. The random sequence was generated by the investigators using Excel, and participants were allocated to the TSWA group, the OSWA group, and the WL group in a 1:1:1 ratio. Allocation slips corresponding to the random sequence were prepared in advance, folded, and placed in a sealed box. Participants drew one folded slip from the box in the order of enrollment, and group assignment was determined accordingly. Outcome assessors and statisticians were blinded to group allocation throughout the study. Owing to the nature of the acupuncture intervention and the waiting-list control design, neither the treating acupuncturist nor the participants were blinded.
Interventions
Participants in both acupuncture groups received bilateral Jingbailao (EX-HN15) and Jianzhongshu (SI15). Sterile disposable needles (0.30 × 40 mm) were inserted into the local muscle layer to a depth of approximately 20 mm. After manual manipulation to elicit deqi, the needles were connected to a KWD-808-I electroacupuncture device. A sparse wave at 2 Hz was applied, with the stimulation intensity adjusted to each participant’s tolerance, and stimulation was maintained for 30 min before needle withdrawal. All electroacupuncture treatments were administered by the same licensed acupuncturist throughout the study to minimize therapist-related variability. Safe needling of the cervicothoracic and upper back regions was emphasized throughout treatment to avoid adverse events caused by excessive needle penetration.
Participants in the TSWA group received treatment once every other day, for a total of three sessions per week, over 4 consecutive weeks. Participants in the OSWA group received treatment once weekly for 4 consecutive weeks. Participants in the WL group entered a waiting period after completing the baseline assessment and received no intervention during the 4-week observation period. They underwent outcome assessments at the same time points as the acupuncture groups and were subsequently offered compensatory treatment.
Outcomes
Primary Outcome
The main assessment time points were baseline, week 4 after treatment, and 4 weeks after completion of treatment. The primary outcome was the Northwick Park Questionnaire (NPQ), which was used to assess neck pain-related functional disability in daily life.
Secondary outcomes
Secondary outcomes included the Visual Analogue Scale (VAS), the Short-Form McGill Pain Questionnaire (SF-MPQ), pain perception threshold (PPT), and pain tolerance threshold (PTO).
NPQ, VAS, and SF-MPQ were assessed at baseline, week 4 after treatment, and 4 weeks after completion of treatment. PPT and PTO were assessed at baseline and week 4 after treatment. Adverse events occurring during treatment were also recorded to evaluate the safety of the intervention.
PPT and PTO were measured bilaterally using a Wagner FDK10 force gauge (Wagner Instruments, Italy), with results expressed in kg/cm2. A 0.5 cm2 probe was placed perpendicular to the measurement point. Pressure was gradually applied until the participant first perceived pain and instructed the assessor to stop; the displayed pressure value was recorded as the pain perception threshold (PPT). Testing was then continued until the participant could no longer tolerate the stimulus, and this value was recorded as the pain tolerance threshold (PTO). The measurement sequence was repeated three times, with an interval of 10–40 s between measurements, and the mean of the three measurements was used for analysis.
Sample Size
Based on previous literature, the change in NPQ score before and after treatment was used for sample size estimation. The mean difference ± standard deviation was 6.11 ± 4.67 in the TSWA group and 19.16 ± 12.43 in the WL group. With α set at 0.05 (two-sided) and β at 0.10 (power = 0.90), PASS 26.0 software was used to calculate a required sample size of 22 participants per group. After accounting for a 20% dropout rate, at least 28 participants were required in each group. The sample size formula was as follows:
n = [(k−1)(Z1₋α/2 + Z1₋β)2 × s2] / [Σi₌1k(μi − μ)2]
Because the planning estimate was based on the TSWA-versus-WL contrast for the primary outcome, the initial calculation provided a minimum per-group requirement rather than a separate three-arm omnibus estimate. After allowing for a 20% dropout rate, at least 28 participants were required per group. To preserve balanced 1:1:1 allocation and provide modest additional precision for the three-arm comparison, 30 participants were enrolled in each group, yielding a total sample size of 90.
Statistical Analysis
The primary analysis followed the intention-to-treat (ITT) principle, whereby all randomized participants were analyzed according to their originally assigned groups. Missing outcome data were handled using multiple imputation, and the imputation model included treatment group, baseline outcome measures, and covariates related to both the outcome and the missing-data mechanism. Continuous variables are presented as the mean (SD) or median (interquartile range), while categorical variables are presented as the number and percentages. For baseline comparisons, categorical variables such as sex were analyzed using the χ2-test, whereas continuous variables such as age and disease duration were analyzed using one-way analysis of variance (ANOVA) when the assumptions of normality and homogeneity of variance were met, or the Kruskal–Wallis test when these assumptions were not met. For the primary and secondary outcomes, between-group comparisons at a single time point were performed using One-Way ANOVA when data were normally distributed with equal variances, or the Kruskal–Wallis test otherwise; when the overall group difference was statistically significant, pairwise comparisons were further conducted with Bonferroni correction. For between-group comparisons across multiple time points, Linear Mixed-Effects Models (LME) were used, with group, time, and group-by-time interaction included as fixed effects and participant included as a random effect, to evaluate between-group differences in changes over time under different treatment frequencies. All statistical tests were two-sided, and P < 0.05 was considered statistically significant.
Results
A total of 90 young adults with CNP were randomly assigned to the TSWA group (n = 30), OSWA group (n = 30), or WL group (n = 30). One participant in the TSWA group and one in the OSWA group withdrew after treatment. According to the ITT principle, all randomized participants were included in the final analysis, and missing outcome data were handled using multiple imputation (Figure 1).
Figure 1.
Trial flow chart.
Abbreviations: TSWA, 3 sessions per week of acupuncture; OSWA, 1 session per week of acupuncture; WL, waiting-list; ITT, intention-to-treat.
Baseline characteristics were comparable among the three groups. Overall, 71 participants were female and 19 were male. There was no significant between-group difference in sex distribution (P = 0.935). Likewise, no statistically significant between-group differences were observed in age, disease duration, or any baseline outcome measures, including NPQ, VAS, SF-MPQ, PPT, and PTO (all P > 0.05), indicating good baseline comparability across groups (Table 1).
Table 1.
Participant Demographic and Baseline Characteristics
| Variable | TSWA (n=30) | OSWA (n=30) | WL (n=30) | P Value |
|---|---|---|---|---|
| Female, n (%) | 23 (76.7%) | 24 (80.0%) | 24 (80.0%) | 0.935 |
| Age, y, median (IQR) | 25.00 (24.00, 25.75) | 25.50 (24.00, 27.00) | 26.00 (24.25, 27.00) | 0.244 |
| Duration of disease, y, median (IQR) | 2.00 (1.42, 3.00) | 2.00 (1.10, 3.00) | 2.35 (1.62, 3.00) | 0.697 |
| NPQ, %, median (IQR) | 36.85 (30.75, 43.73) | 36.10 (28.88, 41.70) | 34.40 (25.00, 40.17) | 0.272 |
| VAS, score, median (IQR) | 5.00 (4.00, 6.00) | 5.00 (4.25, 5.75) | 5.00 (4.00, 6.00) | 0.920 |
| SF-MPQ, score, median (IQR) | 17.50 (16.00, 21.00) | 17.00 (15.00, 20.75) | 18.00 (16.00, 20.50) | 0.853 |
| PPT, kg/cm2, median (IQR) | 1.50 (1.47, 1.65) | 1.58 (1.32, 1.67) | 1.50 (1.40, 1.67) | 0.917 |
| PTO, kg/cm2, mean (SD) | 3.63 (0.91) | 3.34 (0.66) | 3.20 (0.77) | 0.107 |
Abbreviations: NPQ, Northwick Park Questionnaire; VAS, visual analogue scale; SF-MPQ, Short-Form McGill Pain Questionnaire; PPT, pain perception threshold; PTO, pain tolerance threshold; TSWA, 3 sessions per week of acupuncture; OSWA, 1 session per week of acupuncture; WL, waiting-list; IQR, interquartile range.
NPQ
LME analysis showed a significant group-by-time interaction for NPQ (P < 0.001). At baseline, NPQ scores did not differ significantly among the three groups (P = 0.272). After 4 weeks of treatment, a significant between-group difference was observed (P < 0.001), with NPQ scores of 16.15 (12.50, 22.20) in the TSWA group, 25.00 (16.40, 27.33) in the OSWA group, and 32.25 (25.00, 38.58) in the WL group. Bonferroni-adjusted pairwise comparisons showed that NPQ scores were significantly lower in the TSWA group than in the OSWA group (P = 0.0196) and the WL group (P < 0.001), and were also significantly lower in the OSWA group than in the WL group (P = 0.0025).
For the follow-up analysis, only the two acupuncture groups were compared. LME still showed a significant group-by-time interaction for NPQ (P < 0.001). However, at 4 weeks after treatment completion, no significant difference in NPQ scores was observed between the TSWA and OSWA groups [28.25 (7.80) vs 29.14 (7.48), P = 0.656] (Figure 2 and Table 2).
Figure 2.
NPQ scores during the study. Vertical bars represent 95% confidence interval. *P < 0.05, ** P < 0.01, *** P < 0.001.
Abbreviations: NPQ, northwick park questionnaire; TSWA, 3 sessions per week of acupuncture; OSWA, 1 session per week of acupuncture; WL, waiting-list.
Table 2.
Primary and Secondary Outcomes
| Variable | TSWA | OSWA | WL | P Value Between Groups |
|---|---|---|---|---|
| NPQ | ||||
| Baseline | 36.85 (30.75, 43.73) | 36.10 (28.88, 41.70) | 34.40 (25.00, 40.17) | 0.272 |
| Week 4 | 16.15 (12.50, 22.20) | 25.00 (16.40, 27.33) | 32.25 (25.00, 38.58) | <0.001 |
| Follow-up | 28.25 (7.80) | 29.14 (7.48) | - | 0.656 |
| VAS | ||||
| Baseline | 5.00 (4.00, 6.00) | 5.00 (4.25, 5.75) | 5.00 (4.00, 6.00) | 0.920 |
| Week 4 | 2.00 (1.00, 2.00) | 2.00 (2.00, 3.00) | 4.00 (4.00, 5.00) | <0.001 |
| Follow-up | 3.00 (2.12, 3.75) | 3.55 (3.00, 4.00) | - | 0.007 |
| SF-MPQ | ||||
| Baseline | 17.50 (16.00, 21.00) | 17.00 (15.00, 20.75) | 18.00 (16.00, 20.50) | 0.853 |
| Week 4 | 8.00 (6.25, 9.00) | 9.50 (8.25, 12.00) | 17.00 (14.25, 19.00) | <0.001 |
| Follow-up | 12.00 (10.00, 14.00) | 12.00 (10.36, 15.00) | - | 0.451 |
| PPT | ||||
| Baseline | 1.50 (1.47, 1.65) | 1.58 (1.32, 1.67) | 1.50 (1.40, 1.67) | 0.917 |
| Week 4 | 2.10 (1.80, 2.20) | 1.90 (1.80, 2.00) | 1.50 (1.40, 1.70) | <0.001 |
| PTO | ||||
| Baseline | 3.63 (0.91) | 3.34 (0.66) | 3.20 (0.77) | 0.107 |
| Week 4 | 4.35 (4.03, 5.10) | 3.90 (3.60, 4.18) | 3.20 (2.70, 3.55) | <0.001 |
Notes: For PPT at week 4, Bonferroni-adjusted pairwise comparisons were: TSWA vs OSWA, P = 0.0869; TSWA vs WL, P < 0.001; OSWA vs WL, P < 0.001.
Abbreviations: NPQ, Northwick Park Questionnaire; VAS, visual analogue scale; SF-MPQ, Short-Form McGill Pain Questionnaire; PPT, pain perception threshold; PTO, pain tolerance threshold; TSWA, 3 sessions per week of acupuncture; OSWA, 1 session per week of acupuncture; WL, waiting-list.
VAS
A significant group-by-time interaction was observed for VAS (P < 0.001). At baseline, VAS scores were comparable among the three groups (P = 0.920). After 4 weeks of treatment, the between-group difference was statistically significant (P < 0.001), with VAS scores of 2.00 (1.00, 2.00) in the TSWA group, 2.00 (2.00, 3.00) in the OSWA group, and 4.00 (4.00, 5.00) in the WL group. Bonferroni-adjusted pairwise comparisons showed that the TSWA group had significantly lower VAS scores than the OSWA group (P = 0.0042) and the WL group (P < 0.001), and that the OSWA group also had significantly lower scores than the WL group (P < 0.001).
In the follow-up comparison between the two acupuncture groups, the group-by-time interaction for VAS remained significant (P < 0.001). At 4 weeks after treatment completion, VAS scores remained significantly lower in the TSWA group than in the OSWA group [3.00 (2.12, 3.75) vs 3.55 (3.00, 4.00), P = 0.007] (Figure 3 and Table 2).
Figure 3.
VAS scores during the study. Vertical bars represent 95% confidence intervals. **P < 0.01, ***P < 0.001.
Abbreviations: VAS, visual analogue scale; TSWA, 3 sessions per week of acupuncture; OSWA, 1 session per week of acupuncture; WL, waiting-list.
SF-MPQ
The group-by-time interaction for SF-MPQ was significant (P < 0.001). No significant between-group difference was found at baseline (P = 0.853). After 4 weeks of treatment, SF-MPQ scores differed significantly among the three groups (P < 0.001), with scores of 8.00 (6.25, 9.00) in the TSWA group, 9.50 (8.25, 12.00) in the OSWA group, and 17.00 (14.25, 19.00) in the WL group. Bonferroni-adjusted pairwise comparisons showed that SF-MPQ scores were significantly lower in the TSWA group than in the OSWA group (P = 0.0200) and the WL group (P < 0.001), and were also significantly lower in the OSWA group than in the WL group (P < 0.001).
In the follow-up analysis comparing the two acupuncture groups, the group-by-time interaction remained significant (P = 0.013). However, at 4 weeks after treatment completion, no significant difference in SF-MPQ scores was found between the TSWA and OSWA groups [12.00 (10.00, 14.00) vs 12.00 (10.36, 15.00), P = 0.451] (Figure 4 and Table 2).
Figure 4.
SF-MPQ scores during the study. Vertical bars represent 95% confidence intervals. *P < 0.05, ***P < 0.001.
Abbreviations: SF-MPQ, short-form mcGill pain questionnaire; TSWA, 3 sessions per week of acupuncture; OSWA, 1 session per week of acupuncture; WL, waiting-list.
PPT
A significant group-by-time interaction was observed for PPT (P < 0.001). PPT did not differ significantly among the three groups at baseline (P = 0.917). After 4 weeks of treatment, a significant between-group difference was observed (P < 0.001), with PPT values of 2.10 (1.80, 2.20) in the TSWA group, 1.90 (1.80, 2.00) in the OSWA group, and 1.50 (1.40, 1.70) in the WL group. Bonferroni-adjusted pairwise comparisons showed that PPT was significantly higher in the TSWA group than in the WL group (P < 0.001), and significantly higher in the OSWA group than in the WL group (P < 0.001), whereas the difference between the TSWA and OSWA groups was not statistically significant (P = 0.0869) (Figure 5 and Table 2).
Figure 5.
PPT during the study. Vertical bars represent 95% confidence intervals. ***P < 0.001.
Abbreviations: PPT, pain perception threshold; TSWA, 3 sessions per week of acupuncture; OSWA, 1 session per week of acupuncture; WL, waiting-list.
PTO
The group-by-time interaction for PTO was significant (P < 0.001). No significant between-group difference was detected at baseline (P = 0.107). After 4 weeks of treatment, PTO differed significantly among the three groups (P < 0.001), with values of 4.35 (4.03, 5.10) in the TSWA group, 3.90 (3.60, 4.18) in the OSWA group, and 3.20 (2.70, 3.55) in the WL group. Bonferroni-adjusted pairwise comparisons showed that PTO was significantly higher in the TSWA group than in the OSWA group (P = 0.0038) and the WL group (P < 0.001), and was also significantly higher in the OSWA group than in the WL group (P < 0.001) (Figure 6 and Table 2).
Figure 6.
PTO during the study. Vertical bars represent 95% confidence intervals. **P < 0.01, ***P < 0.001.
Abbreviations: PTO, pain tolerance threshold; TSWA, 3 sessions per week of acupuncture; OSWA, 1 session per week of acupuncture; WL, waiting-list.
Discussion
The present study compared the effects of TSWA, OSWA, and WL in young adults with chronic neck pain. The results showed that, after 4 weeks of treatment, both TSWA and OSWA were superior to WL in terms of pain, functional disability, and pain threshold-related outcomes. Moreover, TSWA was superior to OSWA with respect to NPQ, VAS, SF-MPQ, and PTO, suggesting that, under the same acupoint prescription, treatment duration, and stimulation parameters, a higher treatment frequency may yield greater short-term clinical benefit. Follow-up analyses further showed that the advantage of TSWA over OSWA was retained only for VAS, whereas the between-group differences in NPQ and SF-MPQ were no longer statistically significant. These findings suggest that the principal value of a higher treatment frequency may lie in its ability to produce a more rapid onset of effect and greater short-term improvement, whereas its superiority in some outcomes may not be fully maintained through the end of follow-up.
These findings are broadly consistent with the current evidence base for chronic neck pain. Current guidelines and guideline overviews emphasize that the management of chronic neck pain should be based on conservative and multimodal approaches, in which non-pharmacological interventions play a central role.17 Acupuncture, as a widely used non-pharmacological therapy, has been supported by individual patient data meta-analyses for chronic pain overall,18 and randomized controlled trials and systematic reviews in chronic neck pain have also shown that acupuncture can improve pain and function, with some persistence of effect after treatment.7,8 Accordingly, the importance of the present study does not lie in re-establishing whether acupuncture is effective, but rather in addressing a more clinically meaningful question: whether different treatment frequencies influence the magnitude of benefit and the pattern of treatment maintenance.
The superiority of TSWA over OSWA at week 4 may be interpreted from the perspective of the acupuncture dose-response relationship. In recent years, discussion of acupuncture “dose” has expanded beyond acupoint selection alone to include a more comprehensive intervention framework encompassing stimulation parameters, treatment course, and treatment frequency. Methodological work has suggested that acupuncture dose is not determined solely by a single needling session, but by the combined effects of stimulation modality, stimulation intensity, retention time, number of treatment sessions, and treatment interval.12,19 More specifically, a scoping review on treatment frequency indicated that the relationship between acupuncture frequency and efficacy may be disease-specific and potentially nonlinear, with higher-frequency regimens in some pain conditions being associated with faster onset and greater short-term benefit.14 Within this framework, the present results suggest that, in young adults with chronic neck pain, increasing treatment frequency from once weekly to three times weekly may enhance the cumulative therapeutic effect over a short time window, thereby producing more rapid improvements in pain relief, functional recovery, and pain threshold modulation. At the same time, not all outcomes appeared equally sensitive to changes in frequency. TSWA showed an advantage over OSWA for PTO, whereas the between-group difference in PPT did not reach statistical significance. This pattern suggests that the additional benefit conferred by a higher treatment frequency may be more readily reflected in patient-reported pain experience and overall pain tolerance than in every objective threshold measure.
One possible explanation for the stronger week-4 effect with TSWA is temporal accumulation of repeated stimulation. When sessions are delivered at shorter intervals, analgesic and neuromodulatory effects from one session may overlap with subsequent sessions, potentially enhancing cumulative modulation of nociceptive processing. Repeated electroacupuncture may also influence central pain-regulatory networks and descending inhibitory processes; however, these mechanisms were not directly measured in the present trial. This interpretation should therefore be regarded as hypothesis-generating rather than as mechanistic evidence.
Another noteworthy finding was that the maintenance pattern differed across outcomes during follow-up. In the linear mixed-effects models, NPQ, VAS, and SF-MPQ all showed significant group-by-time interactions, indicating that the overall trajectories differed between TSWA and OSWA. However, at the follow-up endpoint, only VAS remained significantly different between groups. This suggests that the primary advantage of TSWA may lie in a faster rate of improvement and greater short-term benefit, rather than in a uniformly sustained long-term superiority across all outcome domains. In other words, a higher-frequency regimen may be more suitable as an initial intensified treatment strategy, particularly for patients requiring rapid symptom relief, whereas the lower-frequency regimen, although slower to take effect, may eventually approach the higher-frequency regimen for some outcomes. This interpretation is consistent with previous evidence on the persistence of acupuncture effects in chronic pain, which indicates that some benefit is often retained after treatment cessation, although durability may vary across outcome dimensions.8,18
From a clinical decision-making perspective, treatment frequency may therefore be individualized according to patient goals and resource constraints. A three-times-weekly regimen may be preferable when rapid symptom relief is a priority, whereas once-weekly treatment may reduce visit burden and resource use for patients with time, travel, or economic constraints, particularly because between-group differences in NPQ and SF-MPQ were no longer evident at follow-up. These findings also support future evaluation of staged schedules, such as an initial higher-frequency phase followed by lower-frequency maintenance, rather than assuming that a single frequency is optimal for all patients.
Nevertheless, several limitations should also be acknowledged. First, this was a single-center study with a relatively limited sample size, and the study population was restricted to young adults; therefore, generalizability should be interpreted with caution. Second, participants and the treating acupuncturist could not be blinded, which may have influenced subjective outcomes through expectation or performance effects, although outcome assessors and statisticians were blinded. Third, allocation was implemented by participants drawing folded slips from a sealed box. Although the sequence itself was randomly generated, this procedure does not provide the same degree of allocation concealment as centralized randomization or sequentially numbered opaque sealed envelopes and may introduce selection bias. Fourth, the waiting-list control did not control for nonspecific effects such as treatment attention, expectancy, or provider interaction; comparisons with WL therefore cannot isolate the specific physiological effect of electroacupuncture. Fifth, only two treatment frequencies were tested, which is insufficient to define a complete frequency-response curve. Finally, follow-up was limited to 4 weeks after treatment, and compensatory treatment in the WL group prevented long-term parallel comparison among all three groups. Future multicenter trials with larger samples, more frequency gradients, stronger allocation concealment, an attention- or sham-controlled comparator, and longer follow-up are warranted.
In conclusion, compared with waiting-list control, both three sessions per week and one session per week of acupuncture improved pain, functional disability, and selected pain threshold measures in young adults with chronic neck pain. Among these regimens, three sessions per week produced faster and more pronounced short-term clinical benefit, whereas its long-term advantage was not consistent across all outcome dimensions. These findings provide direct clinical evidence for optimizing acupuncture treatment frequency in young adults with chronic neck pain and may help shift acupuncture research from the question of “whether it works” toward the more practice-oriented question of “how it can be optimally delivered.”
Funding Statement
This study was supported by the National Natural Science Foundation of China (81873381).
Data Sharing Statement
The datasets generated during and/or analyzed during the current study are available from the corresponding author upon reasonable request.
Disclosure
The authors report no conflicts of interest in this work.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The datasets generated during and/or analyzed during the current study are available from the corresponding author upon reasonable request.