Abstract
ObjectiveTo evaluate the effects of study participation per se at the beginning of a sleep extension trial between screening, randomization, and the run-in visit.DesignSubjects were screened, returned for randomization (Comparison vs. Intervention) after 81 days (median), and attended run-in visit 121 days later.SettingOutpatient.PatientsObese (N = 125; M/F, 30/95; Blacks/Whites/Other, N = 73/44/8), mean weight 107.6±19.7 kg, <6.5 h sleep/night.InterventionNon-pharmacological sleep extension.MeasurementsSleep duration (diaries and actigraphy watch), sleep quality (Pittsburgh Sleep Quality Index), daily sleepiness (Epworth Sleepiness Scale), fasting glucose, insulin and lipids.ResultsPrior to any intervention, marked improvements occurred between screening and randomization. Sleep duration increased (diaries: 357.4 ±51.2 vs. 388.1±48.6 min/night; mean±SD; P<0.001 screening vs. randomization; actigraphy: 344.3 ±41.9 vs. 358.6±48.2 min/night; P<0.001) sleep quality improved (9.1±3.2 vs. 8.2±3.0 PSQI score; P<0.001), sleepiness tended to improve (8.9±4.6 vs. 8.3±4.5 ESS score; P = 0.06), insulin resistance decreased (0.327±0.038 vs. 0.351±0.045; Quicki index; P<0.001), and lipids improved, except for HDL-C. Abnormal fasting glucose (25% vs. 11%; P = 0.007), and metabolic syndrome (42% vs. 29%; P = 0.007) both decreased. In absence of intervention, the earlier metabolic improvements disappeared at the run-in visit.LimitationsRelatively small sample size.ConclusionsImprovements in biochemical and behavioral parameters between screening and randomization changed the “true” study baseline, thereby potentially affecting outcome. While regression to the mean and placebo effect were considered, these findings are most consistent with the “Hawthorne effect”, according to which behavior measured in the setting of an experimental study changes in response to the attention received from study investigators. This is the first time that biochemical changes were documented with respect to the Hawthorne effect. The findings have implications for the design and conduct of clinical research.Trial RegistrationClinicalTrials.gov NCT00261898.
Highlights
Prior to any intervention, marked improvements occurred between screening and randomization
The earlier metabolic improvements disappeared at the run-in visit
While regression to the mean and placebo effect were considered, these findings are most consistent with the ‘‘Hawthorne effect’’, according to which behavior measured in the setting of an experimental study changes in response to the attention received from study investigators
Summary
Since the first prospective report in 2004 of an inverse association between short sleep and body mass index (BMI) in a cohort of 496 young adults followed for 13 years [1], a growing body of evidence has accumulated on the negative consequences of sleep deprivation on weight, metabolism, and the endocrine system. A meta-analysis of 45 studies with a total of more than 600,000 children and adults reported an increased risk of obesity in subjects with short sleep duration (odds ratio: 1.55, adults; 1.89, children) [4]. The existence of an inverse relationship between short sleep and BMI is undisputed [5] especially in obese subjects [6], but it remains to be established whether extending sleep would result in weight loss. A 6 year, large, longitudinal study found that subjects sleeping on average less than 6 h/night gained over time approximately 60% more visceral fat than subjects sleeping more than 9 h/night [8]
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