Is snoozing bad for you? What the evidence actually says

Is snoozing bad for you?

For most healthy adults, no — not in the way it is usually claimed. The best controlled study found a 30-minute snooze cost about six minutes of sleep, with no harm to cognition, cortisol or mood. Snoozing is associated with slightly worse sleep quality and a longer groggy start, and it is a poor substitute for enough sleep. But it is not doing you damage.

This is a subject where the headlines openly contradict each other. The Sleep Foundation runs a piece titled “Hitting the Snooze Button May Actually be Good for You”. Cleveland Clinic runs one quoting a sleep psychologist saying you should minimise it. Both are reputable. Both are, in a narrow sense, correct.

The reason is that they are describing different studies that asked different questions. Once you separate those questions the picture is much clearer than the coverage suggests.

What happens when you hit snooze

Your sleep in the last hour before your alarm is mostly light sleep — stages N1 and N2 — with REM periods that lengthen toward morning. Deep, slow-wave sleep is largely behind you by then. That matters, because the cost of being woken depends enormously on which stage you are woken from.

Being pulled out of slow-wave sleep produces the worst grogginess. Being nudged out of light sleep produces much less. The Stockholm lab study monitored this directly and found that, during a 30-minute snooze period, none of its 31 participants was woken from slow-wave sleep. By that hour of the morning, there was very little of it to wake them from.

The case that snoozing is fine

The strongest evidence here is the 2024 Journal of Sleep Research paper by Sundelin and colleagues — a survey of 1,732 adults plus a controlled two-morning lab study of 31 habitual snoozers.

• Participants got over 20 minutes of genuine sleep during a 30-minute snooze window.
• The net cost to the night was about six minutes of total sleep.
• Cognitive tests taken straight afterwards — processing speed, episodic memory, executive function, arithmetic — were unchanged or slightly better than after an abrupt single wake-up.
• Cortisol was measured directly and showed no adverse effect, nor did morning tiredness, mood, or overall sleep architecture.

The case that snoozing is bad

Two findings pull the other way, and they should not be waved off.

The Notre Dame study of 450 professionals over ten months found habitual snoozers had a resting heart rate about 1.9 bpm higher across the whole night, and in the final hour 2.2% more light sleep and 1.9% less deep sleep. Note the direction of that association, though: it holds at the level of people who snooze, not nights on which they snoozed. On actual snoozing days, resting heart rate was lower. Snoozing may be a marker of something — short sleep, late chronotype, a job that starts too early — as much as a cause.

The stronger objection is the Japanese work by Ogawa and colleagues, which found that snooze alarms prolong sleep inertia relative to a single alarm. The mechanism they describe is “repeated forced awakenings”: sleep in the last twenty minutes gets fragmented, reaction times slow, and the number of stage transitions climbs.

Why both results are right

Sundelin tested a designed 30-minute snooze with a known end. Ogawa tested repeated forced awakenings from the same alarm with no defined end. Those are different behaviours. The evidence does not say “snoozing is fine” or “snoozing is harmful” — it says the structure of the snooze is what determines which one you get.

That reading also explains the survey data. In Ogawa’s sample, 70.5% of students said they snoozed mainly to reduce anxiety about oversleeping. That is not a description of rest. It is a description of a half hour spent repeatedly checking you have not failed — which is exactly the kind of morning that would fragment sleep and stretch out grogginess.

When snoozing genuinely is a problem

• When it is standing in for sleep you did not get. Six minutes recovered from a snooze does not offset ninety minutes lost the night before. Nothing in this research argues otherwise.
• When you have somewhere to be and no fixed end. The risk of snoozing is not physiological, it is logistical. It is missing the train.
• When you are exhausted every single morning regardless. Persistent unrefreshing sleep can point to sleep apnoea, a circadian rhythm disorder, depression, thyroid problems, or medication effects — none of which an alarm can fix. That is a conversation for a doctor.
• When you sleep through everything anyway. If you have dismissed alarms without any memory of doing it, the design of the alarm matters more than the snoozing debate — see how to stop hitting snooze.

So should you stop?

If snoozing is working for you — you get up on time, you feel reasonably human, you are sleeping enough overall — the evidence does not support telling you to stop. The instruction to “set one alarm and get up” is clean advice that most people cannot follow, and the failure to follow it turns out to cost about six minutes.

What is worth changing is the shape. Give the window a fixed end you chose while awake, vary what the alarms sound like so you cannot habituate to them, and stop making snooze-or-dismiss decisions in a state where you are not competent to make them. That is roughly the difference between the two studies, and it is entirely under your control.

It is also, more or less, what Slowrise does: a ladder of alarms across a window you set once, gentle at the start and non-negotiable at the deadline.