Repeating Patterns of Sleep Restriction and Recovery: Do We Get Used to It?

This laboratory-controlled randomized crossover study subjected 14 healthy adults to repeating cycles of sleep restriction (4 hours/night for 3 nights) followed by recovery sleep (10 hours/night for 3 nights), across multiple restriction-recovery cycles, to assess whether physiological adaptation occurred with repetition.

Subjective stress and sleepiness ratings adapted across cycles — participants reported feeling less impaired despite similar objective sleep restriction. However, physiological stress markers did not adapt: cortisol and IL-6 remained elevated after sleep restriction and did not normalize during the recovery periods. Inflammatory activation persisted across repeated restriction-recovery cycles.

The cardiovascular relevance is indirect but meaningful. Chronic sleep restriction elevates inflammatory markers (IL-6, CRP) and cortisol — both of which are established cardiovascular risk factors. The dissociation between subjective adaptation (feeling fine) and physiological activation (systemic inflammation) is particularly important: it means patients with habitual short sleep may underreport its impact because they feel “used to it,” while actually maintaining a chronically elevated inflammatory state.

For cardiovascular risk assessment, persistent sleep restriction should be recognized as a modifiable lifestyle risk factor through the inflammation pathway, alongside diet, exercise, and smoking.

We rate the evidence moderate-limited. A small but carefully controlled crossover study demonstrating that physiological inflammatory responses to sleep restriction do not adapt with repetition despite subjective habituation — relevant context for sleep’s role in cardiovascular risk.