Research

Hormonal

Total sleep time and sleep efficiency are significantly modulated by the circadian phase, being highest when the scheduled sleep episode coincides with the falling and plateau phases of the core body temperature rhythm, and lowest when it coincides with the rising phase.

For the most consolidated sleep, schedule your main sleep block during the time when your body temperature is falling and at its lowest (typically late night/early morning). Avoid scheduling long sleep blocks when your body temperature is rising (late afternoon/early evening), as this leads to shorter, less efficient sleep.

StrongSupportsHIGH confidence
TST and sleep efficiency varied significantly with the phase of the circadian rhythm... TST and sleep efficiency were highest when the midpoint of the scheduled sleep episodes were located on the falling and plateau phase of the curve... TST and sleep efficiency decreased as the midpoint of the scheduled sleep episodes approached the maximum of the rhythm.
Derk‐Jan Dijk et al. · Journal of Neuroscience · 1995

Why this rating

Robust experimental design with forced desynchrony protocol.

Source

Contribution of the circadian pacemaker and the sleep homeostat to sleep propensity, sleep structure, electroencephalographic slow waves, and sleep spindle activity in humans

Derk‐Jan Dijk et al. · Journal of Neuroscience · 1995

DOI 10.1523/jneurosci.15-05-03526.1995

rct · n=8Cited 1,346×
Read the paper
DOI resolved against Crossref · corpus check 2026-06-10

This is one finding among thousands. Every one is graded and traced to its source, so you can see what the evidence actually supports. Browse the research →