Juan Antonio Madrid, physiologist: “A 30‑minute nap? Perfect. Beyond that, you increase the risk of type 2 diabetes"

The physiologist Juan Antonio Madrid has dismantled one of the biggest myths about rest: that everyone needs exactly eight hours of sleep.

“We keep missing the point”

“The first thing I’d get rid of is the idea of the eight hours. No matter how much we insist on it, we keep missing the point,” he told a podcast hosted by the cardiologist and nutritionist Dr. José Abellán.

For Madrid, the problem isn’t just the number - it’s the obsession. “There’s nothing worse for your sleep than worrying about trying to sleep more.” Many people, he notes, go to bed before they’re actually tired or spend extra time lying awake and staring at the clock, which only breeds frustration and insomnia.

For the physiologist, ideal sleep isn’t measured in hours but in how you feel during the day: having steady energy, not feeling irritable, keeping good memory, and not needing multiple cups of coffee just to function until lunchtime. “If I’ve slept well, I’m the best version of myself,” Madrid said. “My personality is operating at 100%. If I’ve slept poorly, I’m at 90, 80, or even 70.” He also breaks down another widely held belief: some people function perfectly well with six hours of deep, high‑quality sleep.

The nap: an ally… as long as it doesn’t drag on

Madrid reminds us that biphasic sleep - rest split between nighttime sleep and an afternoon nap - has been part of human history, especially in summer, when nights were shorter and nighttime rest wasn’t enough. In today’s world, he says, napping can be beneficial: it reduces stress load, can lower blood pressure, and boosts cognitive performance. But there’s a key condition - keep it short.

“Naps that last an hour are too long,” he warns. One reason is what’s called sleep inertia: waking up groggy and disoriented for 20 to 30 minutes. On top of that, an extended nap “steals your sleep hunger and can make nighttime rest harder”.

His recommendation is clear: “A 30‑minute nap? Perfect. Beyond that, you begin to increase the risk of type 2 diabetes.” His warning links overly long naps to potential metabolic issues, reopening the debate over how much - and how - we should be sleeping to protect our health.

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