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Trial registered on ANZCTR


Registration number
ACTRN12618001199202
Ethics application status
Approved
Date submitted
16/07/2018
Date registered
18/07/2018
Date last updated
18/07/2018
Type of registration
Retrospectively registered

Titles & IDs
Public title
Does choice enhance the placebo effect for sleep?
Scientific title
Does choice enhance the placebo effect for sleep?
Secondary ID [1] 295568 0
None
Universal Trial Number (UTN)
U1111-1217-5022
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Sleep difficulty 308838 0
Condition category
Condition code
Neurological 307773 307773 0 0
Other neurological disorders

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
Participants were recruited under the guise of a study investigating how attitudes and lifestyle factors can affect adherence to sleep treatment. Participants were then randomised to one of four groups, placebo with daily choice, placebo with single choice, placebo with no choice, or control (see below). All participants that received placebo treatment (lactose capsules) were told that they would receive a sleep medication for 1 week that had been found to be effective for improving sleep quality.

Placebo daily choice - this group was told that they could choose between two different types of sleep medication (actually lactose placebo capsules) each night. One of the supposed medications was described as 'helping to relax the body and induce sleepiness' whereas the other was described as 'preventing feelings of wakefulness and alertness at bedtime'.

Placebo singe choice - this group was told that they could choose between two different types of sleep medication (actually placebo capsules) at the start of the treatment period and took that 'medication' for the entire week. One of the supposed medications was described as 'helping to relax the body and induce sleepiness' whereas the other was described as 'preventing feelings of wakefulness and alertness at bedtime'.

Placebo no choice - this group was given lactose placebo capsules which were described as either 'helping to relax the body and induce sleepiness' whereas the other was described as 'preventing feelings of wakefulness and alertness at bedtime'. The allocation of the description of the supposed medication in this group was yoked to the decision made by the placebo single choice group.
Intervention code [1] 301864 0
Other interventions
Comparator / control treatment
No treatment control group. This group received no treatment and were told that they were acting as controls.
Control group
Active

Outcomes
Primary outcome [1] 306758 0
Insomnia Severity Index
Timepoint [1] 306758 0
Baseline - the 7 night period prior to treatment
Post-treatment - the 7 night period during treatment
Primary outcome [2] 306759 0
Fatigue Symptom Inventory
Timepoint [2] 306759 0
Baseline - the 7 night period prior to treatment
Post-treatment - the 7 night period during treatment
Secondary outcome [1] 349512 0
Sleep onset latency (i.e. number of minutes taken to fall asleep) measured via:
a) self-report diary
b) actigraphy: assessed using accelerator
Timepoint [1] 349512 0
Baseline - the 7 night period prior to treatment
Post-treatment - the 7 night period during treatment
Secondary outcome [2] 349513 0
Total sleep time (i.e. total number of minutes slept) measured via:
a) self-report diary
b) actigraphy: assessed using accelerator
Timepoint [2] 349513 0
Baseline - the 7 night period prior to treatment
Post-treatment - the 7 night period during treatment
Secondary outcome [3] 349514 0
Perceived Sleep Quality, measured via self-rport rating of sleep quality on a 5 point scale (0 = Very poor to 4 = Very good
Timepoint [3] 349514 0
Baseline - the 7 night period prior to treatment
Post-treatment - the 7 night period during treatment
Secondary outcome [4] 349517 0
Expected efficacy of the (placebo) treatment for improving sleep, measured via three self report questions assessing expectancy from the Credibility/Expectancy Questionnaire.
Timepoint [4] 349517 0
Post-randomisation but prior to receipt of treatment
Secondary outcome [5] 349518 0
Treatment satisfaction, measured via the Treatment Satisfaction Questionnaire for Medicine
Timepoint [5] 349518 0
Post-treatment - at the end of the 7 night treatment period

Eligibility
Key inclusion criteria
Participants were eligible if they self-identified as having sleep difficulty at least three nights per week on average and were at least 18 years old.
Minimum age
18 Years
Maximum age
No limit
Gender
Both males and females
Can healthy volunteers participate?
No
Key exclusion criteria
Participants were ineligible if they had received treatment for sleep difficulty in the past three months, were lactose intolerant, or were taking prescription medication other than the contraceptive pill.

Study design
Purpose of the study
Treatment
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Participants were allocated to groups within sets of four in order to appropriately match participants in the placebo no choice group to the types of 'treatment' delivered in the other groups. The first participant within each set of four was allocated to the single choice group, and the subsequent three participants were randomly allocated to daily choice, no choice, and no treatment control groups, with those in the no choice group receiving placebo treatment yoked to the single choice group
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s


Intervention assignment
Parallel
Other design features
Phase
Type of endpoint(s)
Statistical methods / analysis
Participant data were excluded if they did not answer all items in questionnaires needed to calculate an overall or subscale scores, or if they did not record a particular variable in the sleep diary for four or more nights out of seven. One participant missed a question when completing ISI-A (daily choice group) and FSI (control group) for the treatment week, and one did not return the sleep diary for treatment week (daily choice group), so self-reported SOL and TST could not be calculated. Two participants (daily choice and no choice groups) missed one question in the TSQM.

Planned analyses
One-way analyses of variances (ANOVAs) and chi-square tests of independence were used to compare baseline participant characteristics across groups. Analysis of co-variances (ANCOVAs) with planned orthogonal contrasts were conducted to examine whether there was a difference in sleep outcomes a) between groups that received a placebo treatment (single choice, daily choice, and no choice) and the no treatment control group, b) between groups given a choice (single choice, daily choice) and the no choice group, and c) between single choice and daily choice groups. Baseline scores for ISI-A and FSI composite, as well as TST, SOL and PSQ measured via the sleep diary, and TST and SOL measured via actigraphy, were included as covariates for their respective outcomes. An ANCOVA with planned orthogonal contrasts was also conducted to compare global treatment satisfaction between a) choice and no choice groups, and b) single choice and daily choice groups. To determine whether expectancy mediated the relationship between placebo treatment and sleep outcomes for the placebo groups and no treatment group, mediation analysis was performed using the PROCESS Macro for SPSS. All planned analyses were conducted using the computer software program SPSS (Version 20).

Post hoc analyses
Null hypothesis significant testing (NHST) is increasingly recognised as being inherently limited in terms of providing evidence in favour or a null effect. This is because it can only provide evidence for or against an alternative hypothesis relative to a null hypothesis, the latter of which cannot be taken as positive evidence in favour of the null hypothesis. In light of our results, we therefore conducted post hoc Bayesian analysis to directly estimate the extent to which our data supported no benefit of choice versus some benefit of choice. A one-sample t-test on individual contrast estimates, closely approximates the contrasts run via ANCOVA and can be considered an equivalent test for this purpose when individual contrast estimates are adjusted for the appropriate covariates. Therefore to conduct the Bayesian analysis, we calculated individual contrasts estimates for the choice versus no choice contrast on all sleep outcomes, controlling for gender, relevant baseline score, and the other two contrasts. Then, we used these individual contrast estimates to run Bayesian one-sample t-tests using JASP (V0.8.6, University of Amsterdam). The two hypotheses we compared were that choice has no benefit on the placebo effect (i.e. choice is equivalent to or worse than no choice) versus choice has some benefit (i.e. choice is better than no choice). We used the default Cauchy prior width of 0.707 but also examined and report Bayes Factor Robustness Checks across the full range of Cauchy prior widths (0-1.5) to ensure that the results did not depend on the chosen prior.

Recruitment
Recruitment status
Completed
Date of first participant enrolment
Anticipated
Actual
Date of last participant enrolment
Anticipated
Actual
Date of last data collection
Anticipated
Actual
Sample size
Target
Accrual to date
Final
Recruitment in Australia
Recruitment state(s)
NSW

Funding & Sponsors
Funding source category [1] 300145 0
University
Name [1] 300145 0
University of Sydney
Address [1] 300145 0
School of Psychology, A18
University of Sydney
NSW 2006
Country [1] 300145 0
Australia
Primary sponsor type
University
Name
University of Sydney
Address
University of Sydney
NSW 2006
Country
Australia
Secondary sponsor category [1] 299547 0
None
Name [1] 299547 0
Address [1] 299547 0
Country [1] 299547 0

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 300976 0
University of Sydney Human Research Ethics Committee
Ethics committee address [1] 300976 0
University of Sydney
NSW 2006
Ethics committee country [1] 300976 0
Australia
Date submitted for ethics approval [1] 300976 0
Approval date [1] 300976 0
02/04/2013
Ethics approval number [1] 300976 0

Summary
Brief summary
Choice has been found to facilitate placebo effects in acute conditions where standard placebo treatment without choice has failed to elicit a placebo effect. However, it is unknown whether choice can enhance the placebo effect for longer-term treatments where placebo effects are readily established without choice. This study tested whether either a single or daily choice between two treatments enhanced the placebo effect for sleep difficulty relative to no choice and no treatment over a one-week period.
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 85486 0
A/Prof Ben Colagiuri
Address 85486 0
School of Psychology, A18
University of Sydney
NSW 2006
Country 85486 0
Australia
Phone 85486 0
+61 2 9351 4589
Fax 85486 0
Email 85486 0
ben.colagiuri@sydney.edu.au
Contact person for public queries
Name 85487 0
A/Prof Ben Colagiuri
Address 85487 0
School of Psychology, A18
University of Sydney
NSW 2006
Country 85487 0
Australia
Phone 85487 0
+61 2 9351 4589
Fax 85487 0
Email 85487 0
ben.colagiuri@sydney.edu.au
Contact person for scientific queries
Name 85488 0
A/Prof Ben Colagiuri
Address 85488 0
School of Psychology, A18
University of Sydney
NSW 2006
Country 85488 0
Australia
Phone 85488 0
+61 2 9351 4589
Fax 85488 0
Email 85488 0
ben.colagiuri@sydney.edu.au

No information has been provided regarding IPD availability
Summary results
Have study results been published in a peer-reviewed journal?
Other publications
Have study results been made publicly available in another format?
Results – basic reporting
Results – plain English summary