About The Missing 90 Minutes by Dean Mcdonald:
You did everything right. Early night, dark room, no alarm. And the day still fell apart by three in the afternoon. Nine hours in bed with thirty minutes of deep sleep produces a wrecked day. Seven hours with ninety minutes of deep sleep produces a day where you feel a decade younger. Same person, same bed, opposite outcome. That gap is what this book is about. Dean Mcdonald spent twenty-eight years in technology, wore two sensors on his body, and never once opened the dashboard quietly recording the answer. When he finally looked, the number separating good days from bad was not hours asleep. It was minutes of slow-wave sleep. The book explains what deep sleep does, what quietly erodes it, and which levers actually move it. FREE on Kindle August 21 to 23, 2026.
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Author Bio:
Dean Mcdonald has spent twenty-eight years in technology, working across networks, servers, software, and artificial intelligence, and holds two Masters degrees in Technology. He lives in Sydney, Australia. He spent years wearing two health sensors without ever opening their dashboards, which is exactly the kind of embarrassing admission his writing leads with. The Missing 90 Minutes is his first book: dry, honest about uncertainty, and written for people who follow all the rules and still wake up tired.