Blog

Health technology, privacy-first design, and the research behind what a ring can actually measure.

Closeup of roasted coffee beans scattered on a white surface, representing the source of caffeine that disrupts wearable biometric readings

Latest Sleep · Wearables Why Your Morning Coffee Confuses Your Sleep Tracker: Caffeine, Biometrics, and the False Recovery Signal Caffeine changes your biometrics in ways that look like recovery to a wearable. Higher HRV, elevated resting heart rate, and altered sleep architecture produce a readiness score that says you are rested while your body metabolizes a stimulant. Here is how the blind spot works and what wearables could do about it. James Hoffmann Jun 17, 2026 1 min read Read article

What Your Smart Ring Misses After a Night of Drinking: Alcohol and the Anatomy of a Broken Biometric James Hoffmann Jun 17, 2026 1 min read

Your Health Insurance Company Wants Your Wearable Data. Here Is What That Actually Means. John Hancock, UnitedHealthcare, and Aetna all offer premium discounts for sharing wearable data. The fine print lets them use that same data to raise your rates. Here is how the system works and what you can do about it. James Hoffmann Jun 16, 2026 1 min read

Browse by topic

LATEST ARTICLES

A person holding a phone with a health dashboard visible, looking stressed rather than informed

When Your Health Tracker Makes You Anxious: The Rise of Health Tracking Anxiety A growing body of research shows that wearables and wellness apps can increase stress and trigger obsessive behaviors. Here is what health tracking anxiety looks like, why the industry does not talk about it, and what Pulsyn does differently. James Hoffmann Jun 16, 2026 1 min read

Frost-covered hands in cold weather. The same vasoconstriction that makes your fingers cold also breaks your smart ring optical sensor.

Why Your Smart Ring Fails in Cold Weather: The Vasoconstriction Problem Nobody Mentions Your smart ring's PPG sensor stops working properly when your fingers get cold. Vasoconstriction reduces blood flow to your extremities, and the data quality drops by 50 percent or more. I spent a winter measuring exactly how much, and the numbers are worse than the industry admits. James Hoffmann Jun 15, 2026 1 min read

A dark bedroom with a person lying awake in bed, the kind of scene orthosomnia creates for people who obsess over sleep tracker data

Your Smart Ring Might Be Causing Your Insomnia Your sleep tracker tells you how badly you slept every morning. For a growing number of people, that number is the reason they can't sleep at all. The condition has a name: orthosomnia. James Hoffmann Jun 15, 2026 1 min read

A smartphone showing a health tracking app with cycle data

How Smart Rings Track Your Menstrual Cycle (and What They Get Wrong) Most smart rings track your cycle by measuring skin temperature for a thermal shift around ovulation. The problem is the algorithm defaults to a 28-day cycle that fits about 16% of people. Here is what the clinical evidence actually says and where your temperature data ends up. James Hoffmann Jun 14, 2026 1 min read

A runner training outdoors, with the kind of aerobic effort that wearables try to use for VO2 max estimation through submaximal heart rate analysis

Why Your Wearable's VO2 Max Estimate Is Probably Wrong (and What the Studies Actually Say) Every running watch and fitness tracker claims to estimate your VO2 max. But the number on your wrist and the number from a gas exchange analyzer are different things. Here is what the validation studies actually measure, and why your wearable is probably off by 10 to 15 percent. James Hoffmann Jun 14, 2026 1 min read

A person wearing a smart ring while sleeping, with a digital overlay showing temperature and heart rate data patterns used for early illness detection

Can Your Smart Ring Detect Illness Before You Feel Symptoms A March 2026 Nature study found that sleep and temperature data from consumer wearables can detect diabetes with 73% accuracy. The sensors are already in your smart ring. The companies selling them are not using them for this. James Hoffmann Jun 13, 2026 1 min read