Acupuncture for irritable bowel syndrome: 2-year follow-up of a randomised controlled trial

This study represents an extended follow-up of a randomized clinical trial that evaluated the efficacy of acupuncture in the treatment of irritable bowel syndrome (IBS). The primary objective was to determine whether the clinical benefits previously observed were maintained 24 months after randomization. The research was motivated by the need to understand the durability of acupuncture effects, especially considering that previous studies had suggested sustained benefits in other conditions such as low back pain. The original study recruited 233 adults with IBS from primary care between November 2008 and June 2009.

Participants had persistent symptoms for a mean of 13 years and a minimum score of 100 on the IBS Symptom Severity Scale (IBS-SSS). They were randomized into two groups: 116 patients received up to 10 weekly sessions of individualized traditional acupuncture in addition to usual care, while 117 continued with usual medical care only. Acupuncture was provided by qualified practitioners who performed traditional Chinese diagnosis and offered diagnosis-related lifestyle advice in 68% of cases. Sessions were predominantly weekly during the first 3 months, with patients who attended at least one session completing a mean of 9 of the 10 sessions offered.

The primary outcome was the IBS-SSS score at 24 months, measured on a 0-500 point scale, where lower values indicate less severe symptoms. Secondary outcomes included non-colonic IBS symptoms and quality of life measured by the SF-12. Statistical analysis used an unstructured multivariate linear model, a more robust method for handling missing data compared with traditional analysis of covariance. This model treats follow-up and baseline measurements as correlated outcomes, allowing simultaneous estimation of treatment differences at all time points.

Results showed a 61% response rate at 24 months, with greater loss to follow-up in the control group (47%) compared with the acupuncture group (32%). The adjusted difference in IBS-SSS score at 24 months was -18.28 points (95% CI -40.95 to 4.40) favoring acupuncture but was not statistically significant. This difference represented approximately 80% of the magnitude of the significant effects observed at 6, 9, and 12 months. Interestingly, reanalysis with the multivariate model revealed a significant difference at 12 months (-23.06 points, p = 0.035), which had been only marginally significant in the original analysis.

No significant differences were found in secondary outcomes, except for non-colonic symptoms at 3 months. The clinical implications suggest that, although acupuncture demonstrates sustained benefits up to 12 months, these may gradually diminish after that period. The authors propose that long-term benefits may be related to specific components of acupuncture beyond needling, including traditional Chinese diagnosis and lifestyle advice. The progressive improvement observed in the control group between 12 and 24 months may also have contributed to the reduction in the between-group difference.

The study suggests that the observed effects probably exceed simple placebo responses, given that previous reviews have not demonstrated a sustained placebo response at 12 months in IBS trials. The physiological mechanisms underlying the long-term effects require further investigation. For future research, the authors recommend active controls that provide structural equivalence in non-specific treatment components, such as hypnotherapy or cognitive-behavioral therapy.