Dose-response and efficacy of spinal manipulation for care of cervicogenic headache: a dual-center randomized controlled trial.

Background Context: The optimal number of visits for the care of cervicogenic headache (CGH) with spinal manipulative therapy (SMT) is unknown.

Purpose: The present study aimed to identify the dose-response relationship between visits for SMT and chronic CGH outcomes and to evaluate the efficacy of SMT by comparison with a light-massage control.

Study Design/setting: This is a two-site, open-label randomized controlled trial.

Patient Sample: Participants were 256 adults with chronic CGH.

Outcome Measures: The primary outcome was days with CGH in the previous 4 weeks evaluated at the 12- and 24-week primary end points. Secondary outcomes included CGH days at remaining end points, pain intensity, disability, perceived improvement, medication use, and patient satisfaction.

Methods: Participants were randomized to four dose levels of chiropractic SMT: 0, 6, 12, or 18 sessions. They were treated three times per week for 6 weeks and received a focused light-massage control at sessions when SMT was not assigned. Linear dose effects and comparisons with the no-manipulation control group were evaluated at 6, 12, 24, 39, and 52 weeks. The present study was funded by the National Center for Complementary and Integrative Health (R01AT006330) and is registered at ClinicalTrials.gov (NCT01530321). The authors declare no conflicts of interest.

Results: A linear dose-response was observed for all follow-ups, a reduction of approximately 1 CGH day/4 weeks per additional 6 SMT visits (p<.05); a maximal effective dose could not be determined. Cervicogenic headache days/4 weeks were reduced from about 16 to 8 for the highest and most effective dose of 18 SMT visits. Mean differences in CGH days/4 weeks between 18 SMT visits and control were -3.3 (p=.004) and -2.9 (p=.017) at the primary end points, and were similar in magnitude at the remaining end points (p<.05). Differences between other SMT doses and control were smaller in magnitude (p>.05). Cervicogenic headache intensity showed no important improvement nor differed by dose. Other secondary outcomes were generally supportive of the primary outcome.

Conclusions: There was a linear dose-response relationship between SMT visits and days with CGH. For the highest and most effective dose of 18 SMT visits, CGH days were reduced by half and about 3 more days per month than for the light-massage control.