The Hawthorne Effect: a randomised, controlled trial.
BACKGROUND
The '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.


METHODS
Participants 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).


RESULTS
We 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.


CONCLUSIONS
We 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.


BACKGROUND
Current controlled trials: ISRCTN45577048.
McCarney
Rob
R
Department of Psychological Medicine, Imperial College London, UK. robmccarney@googlemail.com <robmccarney@googlemail.com>
Warner
James
J
Iliffe
Steve
S
van Haselen
Robbert
R
Griffin
Mark
M
Fisher
Peter
P
D000368:Aged; D000369:Aged, 80 and over; D017028:Caregivers; D003071:Cognition / Q000187:drug effects; D016001:Confidence Intervals; D003704:Dementia / Q000188:drug therapy* / Q000453:epidemiology / Q000208:ethnology; D004311:Double-Blind Method; D015987:Effect Modifier, Epidemiologic; D005194:Family Practice; D005260:Female; D020441:Ginkgo biloba; D006801:Humans; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D008517:Phytotherapy; D010919:Placebos; D010936:Plant Extracts / Q000627:therapeutic use*; D011788:Quality of Life; D011795:Surveys and Questionnaires
D010919:Placebos; D010936:Plant Extracts