Hawthorne effect with transient behavioral and biochemical changes in a randomized controlled sleep extension trial of chronically short-sleeping obese adults: implications for the design and interpretation of clinical studies
Abstract
Objective: To evaluate the effects of study participation per se at the beginning of a sleep extension trial between screening, randomization, and the run-in visit.
Design: Subjects were screened, returned for randomization (Comparison vs. Intervention) after 81 days (median), and attended run-in visit 121 days later.
Setting: Outpatient.
Patients: Obese (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.
Intervention: Non-pharmacological sleep extension.
Measurements: Sleep duration (diaries and actigraphy watch), sleep quality (Pittsburgh Sleep Quality Index), daily sleepiness (Epworth Sleepiness Scale), fasting glucose, insulin and lipids.
Results: Prior 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.
Limitations: Relatively small sample size.…
How strong is the evidence?
Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design. Reported size: 125 participants or records.
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