Study record · validation · 1999

Warm feet promote the rapid onset of sleep

Kräuchi K, Cajochen C, Werth E, and Wirz-Justice A

Nature, 401(6748), 36-37 · 1999

Why this study matters to CircaTest

Foundational chronobiology paper widely cited as evidence that distal skin temperature is involved in sleep onset. CircaTest cites it in the 'how sleep trackers work' guide as the editorial basis for why temperature-sensing wearables have a physiological grounding beyond accelerometry and PPG. CircaTest does NOT have direct access to the full paper; this entry exists primarily as a stable citation target so the inline reference in the guide resolves to a verifiable PubMed record. Specific claims about what the paper found should be verified against the linked Nature page.

Abstract

PubMed does not index a structured abstract for this 1999 Nature Brief Communication. CircaTest does not have direct access to the full paper.…

Read the full abstract on the source →

Source: MANUAL · Excerpt for fair-use commentary; full abstract via the source link

Population

Age

not extracted (no PubMed abstract available)

Reference standard

other

PubMed does not provide an abstract or population details for this Brief Communication. Sample size, age range, and study design must be obtained from the full Nature paper linked under sources.

Cite this study

Kräuchi K, Cajochen C, Werth E, and Wirz-Justice A (1999). Warm feet promote the rapid onset of sleep. Nature, 401(6748), 36-37. https://doi.org/10.1038/43366

AI-assembled record · errors are possible

This page was built and is maintained by AI working from the published abstract and PubMed metadata for the cited study. CircaTest does not have access to the full text of every paper in its corpus. Categories of error that have happened on this site and could happen again include:

Per-device metric values inferred when the abstract reports only an aggregate range
Stage-specific accuracy figures pulled from secondary sources rather than the primary paper
Sample size or population characteristics missing from the abstract
Editorial framing in the curatorial note that overstates the study's actual scope
Year typos and author-name transliteration errors

Where a metric value reads see source, the published abstract did not contain that value and CircaTest deliberately left it null rather than guess. For any decision that depends on the underlying numbers, please consult the linked PubMed, PMC, or DOI source directly. Corrections are welcome via the about page.

Source links

Added to the CircaTest meta-analysis on 2026-04-06. How CircaTest evaluates studies →