PpgAccuracySpo2
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