Evidence dashboard · 15 July 2026

What actually helps sleep?

A fast ranking of light, sound, and smartwatch techniques from the Sleep Tight critical literature review.

38references in the full review

26key sources quality-appraised

10techniques ranked below

5watch signal groups considered

01 · Ranked techniques

Evidence before enthusiasm

Ranked by practical value, evidence quality, and risk of disturbing sleep. Expand any row for the reasoning and key papers.

Rank	Technique	Verdict	Key-source count	Confidence

No techniques match these filters.

Counts classify key sources directly appraised—not every paper nested inside a systematic review.

02 · Practical protocol

A routine you can use tonight

The watch observes and records. The scheduled environment does most of the work.

MorningGet bright light

Daylight strengthens the contrast between day and the dim evening.

3 h before bedLower melanopic dose

Aim below 10 lux melanopic EDI at eye level where practical.

45 min before bedStart wind-down

Fade warm, low-melanopic light and optionally play familiar low-arousal music.

Lights-outDarkness and silence

Target below 1 lux melanopic EDI. Use masking only for a real noise problem.

During sleepWatch, don’t react

Record movement and cardiac trends. Do not brighten or raise sound from HR alone.

Morning reviewRate before looking

Record perceived quality and alertness, then compare multi-night watch trends.

03 · Smartwatch use

What your watch can contribute

Useful signals are indirect and probabilistic. Combine them over time; never turn one sample into a diagnosis or a stimulus.

Signals and safe uses

Galaxy Watch4 and later can expose these through Samsung APIs on supported models.

Signal	What it is	Useful marker	Safe product action
Heart rate	Measured from PPG	Deviation from personal sleeping baseline; sustained descent or elevation	Log trends. Never infer mood or increase sound from a single rise.
IBI / pulse variability	Measured intervals, quality-dependent	Autonomic recovery trend across clean, comparable nights	Use next morning and over weeks; reject motion-corrupted intervals.
Movement	Accelerometer	Settling, restlessness, probable awakenings, time in bed	Combine with cardiac data for coarse states and an explicit unknown state.
Respiration / SpO₂	Derived or intermittently measured	Repeated irregularity or desaturation flags from validated vendor features	Context only. Persistent concerns belong with a clinician, not the lamp controller.
Skin temperature	Peripheral trend	Deviation from the user’s baseline; illness or cycle context	Explain unusual nights retrospectively; do not treat it as room temperature.
Sleep stages	Vendor inference	Exploratory multi-night pattern	Morning review only. Do not trigger light or sound from a claimed live stage.

Useful composite markers

These are product research targets, not clinical diagnoses.

Settling probability

Several minutes of lower movement plus a plausible HR descent relative to the same user.

Live · medium confidence

Probable arousal burden

Sustained movement and cardiac change, counted across the night rather than acted on immediately.

Live log · low-medium confidence

Recovery deviation

Sleeping HR above baseline, lower clean-signal HRV, fragmented movement, and poor morning rating.

Morning · trend only

Schedule regularity

Variance in session start, probable sleep onset, and wake time across at least one week.

Weekly · useful

Data confidence

Contact quality, packet completeness, motion artefact, battery, and contradictory channels.

Always · mandatory

04 · Paper highlights

The papers that change the decision

A short reading list spanning consensus, meta-analysis, controlled experiments, and device validation.