Abstract
BackgroundThe 'Hawthorne Effect' may be an important factor affecting the generalisability of clinical research to routine practice, but has been little studied. Hawthorne Effects have been reported in previous clinical trials in dementia but to our knowledge, no attempt has been made to quantify them. Our aim was to compare minimal follow-up to intensive follow-up in participants in a placebo controlled trial of Ginkgo biloba for treating mild-moderate dementia.MethodsParticipants in a dementia trial were randomised to intensive follow-up (with comprehensive assessment visits at baseline and two, four and six months post randomisation) or minimal follow-up (with an abbreviated assessment at baseline and a full assessment at six months). Our primary outcomes were cognitive functioning (ADAS-Cog) and participant and carer-rated quality of life (QOL-AD).ResultsWe recruited 176 participants, mainly through general practices. The main analysis was based on Intention to treat (ITT), with available data. In the ANCOVA model with baseline score as a co-variate, follow-up group had a significant effect on outcome at six months on the ADAS-Cog score (n = 140; mean difference = -2.018; 95%CI -3.914, -0.121; p = 0.037 favouring the intensive follow-up group), and on participant-rated quality of life score (n = 142; mean difference = -1.382; 95%CI -2.642, -0.122; p = 0.032 favouring minimal follow-up group). There was no significant difference on carer quality of life.ConclusionWe found that more intensive follow-up of individuals in a placebo-controlled clinical trial of Ginkgo biloba for treating mild-moderate dementia resulted in a better outcome than minimal follow-up, as measured by their cognitive functioning.Trial registrationCurrent controlled trials: ISRCTN45577048
Highlights
The so-called 'Hawthorne Effect' may be an important factor affecting the generalisability of clinical research to routine practice, but has been little studied
Data on effectiveness of Ginkgo versus placebo, and adverse events will be reported elsewhere. To summarise these findings in the analysis of co-variance (ANCOVA) model with baseline score as a co-variate (n = 176), we found no evidence that a standard dose of high purity Ginkgo biloba confers benefit over placebo in mild-moderate dementia over six months
In the ANCOVA model with baseline score as a co-variate, follow-up group had a significant effect on outcome at six months on the ADAS-Cog score (n = 116; β = -2.376; 95%CI -4.519, 0.233; p = 0.030), which favoured the intensive follow-up group
Summary
The 'Hawthorne Effect' may be an important factor affecting the generalisability of clinical research to routine practice, but has been little studied. The so-called 'Hawthorne Effect' may be an important factor affecting the generalisability of clinical research to routine practice, but has been little studied. The clinician has not taken into account the possible impact of the Hawthorne Effect on the trial results that guide his practice- patients in clinical trials appear to fare better than those in routine practice by virtue of their participation. He may have stopped his patient's medication unnecessarily. The definition has been broadened; here it refers to treatment response rather than productivity
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