Healthspan analyzes nine key metrics to calculate your WHOOP Age and assess whether your body is aging faster or slower than your biological age. Backed by longevity research, Healthspan highlights daily actions that affect your long term health most — and shows you exactly where to improve. WHOOP tracks all four stages of sleep — slow wave sleep (SWS), REM, light, and awake — with near-perfect accuracy. Each stage serves a different purpose in your recovery. Depending on membership, you can add or subtract the biometrics you want. The cost of the device is usually worked into the membership. This will make the price infinitely more affordable.