In 2005, despite considerable prior evidence against echinacea and no scientific plausibility whatsoever, the NCCAM funded this study on echinacea for the common cold, published in NEJM. The study was negative---showing no benefit or evidence of biological effect. Not that it was needed, but it should have been the final nail in the coffin. Despite that state of affairs the NCCAM subsequently announced plans to continue study of echinacea on the ridiculous argumentum ad populum that the public was demanding something be done about colds and echinacea was widely used! I blogged it here, lamenting that NCCAM just couldn't seem to give up, planning to drag it on and on no matter how strong the evidence against it.
Well, surprise, surprise, here are the findings of the Annals study:
Mean global severity was 236 and 258 for the blinded and unblinded echinacea groups, respectively; 264 for the blinded placebo group; and 286 for the no-pill group. A comparison of the 2 blinded groups showed a 28-point trend (95% CI, −69 to 13 points) toward benefit for echinacea (P = 0.089). Mean illness duration in the blinded and unblinded echinacea groups was 6.34 and 6.76 days, respectively, compared with 6.87 days in the blinded placebo group and 7.03 days in the no-pill group. A comparison of the blinded groups showed a nonsignificant 0.53-day (CI, −1.25 to 0.19 days) benefit (P = 0.075). Median change in interleukin-8 levels and neutrophil counts were also not statistically significant (30 ng/L and 1 cell/high-power field [hpf] in the no-pill group, 39 ng/L and 1 cell/hpf in the blinded placebo group, 58 ng/L and 2 cells/hpf in the blinded echinacea group, and 70 ng/L and 1 cell/hpf in the open-label echinacea group)....
Conclusion: Illness duration and severity were not statistically significant with echinacea compared with placebo. These results do not support the ability of this dose of the echinacea formulation to substantively change the course of the common cold.
So will this be the final finishing blow? Not likely. The authors give themselves some wiggle room. From the discussion:
Although these results do not allow us to reject the null hypothesis and confidently claim evidence of benefit, data are also insufficient to exclude the possibility of a clinically significant effect....
...we now conclude that a conventional randomized, controlled trial would need slightly more than 200 people in each of 2 groups to have 80% power to detect a 20% difference in global severity, using the WURSS-21 (61). A trial that used illness duration or prespecified day-to-day change as a primary outcome could be smaller, but the results would be less meaningful. We also note that our results were obtained with only 1 of many possible types of echinacea formulations. Although the dosing and array of phytochemical constituents that we used (Appendix Table) are reasonably representative of currently available echinacea preparations, a substantively different formulation could give substantially different results. Finally, because randomized trials provide results in terms of group averages, they may obscure benefits (or harms) for individuals or subgroups.