The placebo response and effect of time in a trial of acupuncture to treat nausea and vomiting in early pregnancy

https://doi.org/10.1016/S0965-2299(02)00072-9Get rights and content

Abstract

Objectives: The sham control is widely used in acupuncture research, and its adequacy may be assessed by exploring the ‘credibility’ of the intervention. We aimed to examine the credibility of the study intervention, to quantify the size of the placebo response and effect of time in reducing nausea in early pregnancy. Design: Five hundred and ninety-three women with nausea or vomiting in early pregnancy volunteered to participate in a randomised controlled trial, conducted at the Women’s and Children’s Hospital, South Australia. Outcome measures: Women completed the Rhodes Index of Nausea and Vomiting and the Credibility Rating Scale. Results: The credibilities of the acupuncture and sham acupuncture interventions were not different. The relative change in nausea at the end of the first week of the study was estimated to be 28% attributed to a time effect and 7% to the placebo response. At the end of the third week, there was a further small increase in time effect (32%) and the placebo response (17%). Conclusion: Sham acupuncture is a credible control and allows assessment of the size of the placebo response.

Section snippets

INTRODUCTION

Nausea and vomiting in early pregnancy is a self-limiting condition, with women reporting a reduction in their symptoms as their pregnancy progresses towards the end of the first trimester. Clinical trials of interventions to reduce nausea and vomiting in pregnancy which omit a control group in the study design, have reported impressive results. In a recent randomised controlled trial of acupuncture to treat nausea and vomiting in early pregnancy, two control groups were included in the trial

METHODS

Women were volunteers to a randomised controlled trial evaluating the role of acupuncture to treat nausea and vomiting in early pregnancy, conducted at the Women’s and Children’s Hospital, South Australia. Women with a confirmed pregnancy, presenting at less than 14 weeks pregnant, with symptoms of nausea or vomiting were eligible to join the trial. Women were not eligible if there were any signs of clinical dehydration, or reason to suspect their symptoms were not due to their pregnancy. The

STATISTICAL ANALYSIS

It was an entry requirement that women experienced nausea at trial entry. A trial of 114 women would have an 80% power to detect a treatment effect of a 35% reduction in the number of women reporting nausea from 99 to 64% (alpha=0.05). The prevalence of vomiting is reported at 50% and to detect a 35% reduction in vomiting from 50 to 32.5% (alpha=0.05, beta=0.2), a sample size of 592 women was required. The sample size allowed for a 10% loss to follow up (pregnancy loss or withdrawal from the

RESULTS

Five hundred and ninety-three women were randomised to the trial between January 1997 and July 1999. Figure 1 summarises recruitment and return of data forms. We received nausea and vomiting data from 534 (90%) of women at the end of the first week of the trial and data from 443 (75%) at the end of the fourth week of the trial (Fig. 1). Assessments of the credibility of acupuncture was received from 419 (94%) women at baseline and from 391 (88%) women at the end of the study.

The median

WOMEN’S BELIEFS ABOUT ACUPUNCTURE

Women expressed positive views on the logic of acupuncture and confidence in the treatment improving their symptoms (Table 2). Women’s views did not differ between the acupuncture and sham groups at trial entry.

At the end of the trial, there was a difference in women’s views on recommending acupuncture (P<0.01) and their views on the success of acupuncture to treat other conditions between study groups (P<0.01; Table 2). Women’s confidence in recommending acupuncture to their friends was higher

PREVIOUS USE OF ACUPUNCTURE

It was feasible that women with previous acupuncture experience may have different beliefs or knowledge about acupuncture compared with the novice. Sixty-eight (17%) women reported previous acupuncture use. These women recorded higher scores on the logic of the treatment, compared with women who had no previous use of acupuncture (P<0.05; Table 3). Confidence in the treatment did not differ between women with previous acupuncture experience and women with no prior acupuncture experience.

GUESSING STUDY GROUP ALLOCATION

Three hundred and eighty (85%) women guessed which study group they were allocated to, but eight women were unable to guess. The majority of women (272, 71%) thought they were in an active acupuncture group (traditional acupuncture or PC6 acupuncture) and 100 women (26%) thought they were in the sham acupuncture group (Table 4).

We found women’s views on their perceived study group allocation differed according to their actual group allocation (P<0.0001). A higher proportion of women (102, 84%)

ESTIMATION OF THE PLACEBO RESPONSE AND THE EFFECT OF TIME ON NAUSEA

Estimates were made of the placebo response and improvement of nausea over time. Women’s nausea scores by study group (active acupuncture or sham acupuncture) are presented in Table 6.

Our data demonstrated an effect of time contributing to a decline in nausea at the end of the first and third weeks of the study (P<0.001; Table 6). There was no significant placebo response at the end of the first week but a significant placebo response was present at day 21 (P<0.001), and there was evidence that

DISCUSSION

We propose that an important aspect of the placebo response that we were able to explore in this trial was the strength of women’s expectations to improve. Women’s views on joining the study were positive and we suggest the method of recruiting women to the trial may have contributed to these optimistic views. The media was used to great effect to aid recruitment. However, the media sensationalised news of the trial, and women picking up the weekend newspaper were greeted by the heading

Acknowledgements

The authors wish to thank Kristyn Willson for her statistical support to this study.

Caroline Smith PhD, MSc, BSc, Lic Ac, Post-doctoral Research Officer, Department of Obstetrics and Gynaecology, The University of Adelaide, Women’s and Children’s Hospital, 72 King William Road, North Adelaide, SA 5006, Australia. Tel.: +61 88161 7565; Fax: +61 88161 7652; E-mail: [email protected]

References (9)

There are more references available in the full text version of this article.

Cited by (22)

  • The hip

    2010, Acupuncture in Manual Therapy
  • Meta-analysis of Acustimulation Effects on Nausea and Vomiting in Pregnant Women

    2006, Explore: The Journal of Science and Healing
    Citation Excerpt :

    These trials were then evaluated using the Quality of Reports of Meta-analysis of Randomized Controlled Trials (QUOROM) guidelines.23,24 Three papers were excluded because repeated data were used from previous studies,25-27 and six additional papers were excluded because they were case studies.28-33 The remaining 17 papers were then evaluated for the quality of randomization and the quality of treatment.

  • Complementary and alternative medicine in obstetrics

    2005, International Journal of Gynecology and Obstetrics
  • Patients' Expectancies to Acupuncture: A Systematic Review

    2022, Journal of Integrative and Complementary Medicine
View all citing articles on Scopus

Caroline Smith PhD, MSc, BSc, Lic Ac, Post-doctoral Research Officer, Department of Obstetrics and Gynaecology, The University of Adelaide, Women’s and Children’s Hospital, 72 King William Road, North Adelaide, SA 5006, Australia. Tel.: +61 88161 7565; Fax: +61 88161 7652; E-mail: [email protected]

Caroline Crowther MD, FRCOG, FRANZCOG, CMFM, Associate Professor, Department of Obstetrics and Gynaecology, The University of Adelaide, Women’s and Children’s Hospital, 72 King William Road, North Adelaide, SA 5006, Australia

Funding The study was financially supported by the Department of Obstetrics and Gynaecology, the University of Adelaide and the Women’s and Children’s Hospital Research Foundation, Adelaide. Needles were donated by Cathy Herbal Products, Sydney, Australia.

View full text