Posts tagged: Sleep

6 posts found

A person sleeping on their side with a smart ring on their finger, illustrating how body position compresses the finger against a pillow or mattress

Why Your Smart Ring's Nighttime Data Is a Lie: The Sleep Position Problem Nobody Mentions

Your smart ring's PPG sensor assumes your finger is at heart level with unrestricted blood flow. When you sleep on your side, neither of those things is true. Here is what the data actually looks like.

James Hoffmann

Jun 21, 2026 1 min read

A pregnant woman wearing a smart ring, with abstract biometric data lines flowing around her finger

Heart RateBiometricsAlgorithms

Your Smart Ring Has No Idea You're Pregnant: How Pregnancy Breaks Every Biometric Algorithm

Pregnancy raises your resting heart rate by 10 to 20 bpm, drops your HRV, raises your temperature, and changes your sleep architecture. Every wearable algorithm trained on non-pregnant baselines gets this wrong. Here is what the data actually looks like.

James Hoffmann

Jun 21, 2026 1 min read

An alarm clock on a bedside table in soft morning light, showing the gap between weekday wake times and weekend sleep schedules

Circadian RhythmSocial JetlagReadiness

The Social Jetlag Problem: Why Your Weekend Sleep Schedule Is Wrecking Your Recovery Score

Most wearables score Monday morning as poor recovery when the real problem is that their algorithm does not know what time your brain thinks it is. Social jetlag shifts your circadian clock by one to two hours every weekend. The recovery score does not.

James Hoffmann

Jun 10, 2026 15 min read

A hotel room at night with an unmade bed, representing the unfamiliar environment where the first night effect occurs and sleep trackers get confused

First Night EffectOuraScience

How Traveling Breaks Your Sleep Tracker (and Why the First Night Effect Is Real)

The first night effect is a documented neurological phenomenon where half your brain stays awake in unfamiliar environments. Most wearables treat this as a bad night and tank your score. They should be treating it as a different kind of night entirely.

James Hoffmann

Jun 1, 2026 11 min read

Macro photograph of finger skin showing the dense capillary network near the surface. The biological reason transmissive PPG works better at the fingertip than the wrist.

SleepPpgForm Factor

Why the Smart Ring Form Factor Is Better for Sleep Than the Wrist: A Physics Argument

The wrist is the worst place to measure heart rate during sleep. It is too thick for transmissive PPG, too prone to motion artifact, and too thermally unstable. The finger wins on every metric that matters for overnight biometrics.

James Hoffmann

May 29, 2026 13 min read

A serene bedroom scene representing quality sleep

Health TechWearablesSleep

How Pulsyn Calculates Your Sleep Score: A Transparent Look at Our Algorithm

The complete math behind your sleep score. Personalized baselines, five weighted components, and how it compares to polysomnography.

James Hoffmann

Jan 14, 2026 11 min read