Sleep restriction for 1 week reduces insulin sensitivity in healthy men.
Level 2 - randomized trial
Controlled inpatient physiological trial with randomized drug arm
PubMed 20585000 · doi:10.2337/db09-0699
What was done
A 12-day inpatient study evaluated 20 healthy men (aged 20–35 years, BMI 20–30 kg/m²). Participants completed a sleep-replete phase (10 h/night in bed for ≥8 nights, including 3 inpatient nights) followed by a sleep-restricted phase (5 h/night in bed for 7 nights). Subjects were randomized to receive 300 mg/day modafinil or placebo during sleep restriction, while diet and physical activity were strictly controlled. On the last 2 days of each condition, glucose metabolism was assessed using an intravenous glucose tolerance test (IVGTT) and a euglycemic-hyperinsulinemic clamp. Salivary cortisol, 24-h urinary catecholamines, and neurobehavioral performance were also measured.
What was found
IVGTT-derived insulin sensitivity decreased by 20 ± 24% after sleep restriction (P = 0.001), with no significant alterations in insulin secretory response. Clamp-measured insulin sensitivity decreased by 11 ± 5.5% (P < 0.04). Glucose tolerance and disposition index were also reduced by sleep restriction. Modafinil treatment did not alter these metabolic outcomes. Salivary cortisol increased by 51 ± 8% under sleep restriction (P < 0.02), though changes in insulin sensitivity did not correlate with cortisol, urinary catecholamines, or slow-wave sleep.
Why it matters
This study provides experimental evidence that short-term sleep restriction directly impairs insulin sensitivity and glucose tolerance in healthy individuals, independent of diet and physical activity. It also demonstrates that pharmacologically sustaining alertness with modafinil does not prevent metabolic impairment.
Limits
The sample size was small (n = 20) and restricted entirely to healthy young men, limiting generalizability to women, older populations, and individuals with baseline metabolic disorders. The study assessed only short-term (7-day) sleep restriction in a controlled laboratory setting, which may not reflect chronic, fluctuating sleep debt in daily life.
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