Sleep runs in cycles of roughly 90 minutes, each moving from light sleep into deep sleep and then REM sleep, and most people pass through four to six of them a night. Waking briefly at the edges of those cycles is a normal feature of healthy sleep, not a sign that something is broken. What changes the picture is how easily you drift back down afterwards, and that is exactly where new parents and women in perimenopause tend to feel it most.
What is a sleep cycle, and how long does it last?
A sleep cycle is one full pass through the stages of sleep. You begin in light sleep, descend into slow-wave (deep) sleep, then rise through lighter sleep into REM, the stage most linked with vivid dreaming. A meta-analysis of healthy sleepers across the lifespan (Ohayon et al., 2004, Sleep) documented how the proportions of these stages shift with age, which is one reason the shape of your night at 45 is not the shape it had at 25.
The popular “90 minutes” figure is an average, not a rule. Cycles tend to be a little shorter early in the night and longer later, and the stage mix changes as the night goes on. Deep sleep dominates the first half; REM takes up more of the second half. If you want the stage-by-stage detail, our guide to sleep stages explained walks through each one.
Why do I wake up between sleep cycles?
At the end of a cycle, sleep is naturally at its lightest. This is the moment your brain is most open to surfacing, and a small noise, a shift in temperature or a full bladder is more likely to tip you into brief wakefulness. Researchers describe these short events as arousals, and they are a recognised part of normal sleep physiology (Halász et al., 2004, Journal of Sleep Research). Most are over in seconds and never make it into memory.
So waking once or twice a night is common, and not a failing. It becomes noticeable when you stay awake long enough to remember it, or when your mind starts working the moment your eyes open. If that is your pattern, why you wake up multiple times during the night covers the common triggers in more depth.
Why does the night feel so different for new parents?
If you are a new parent, your sleep is being interrupted from two directions at once.
The first is the baby. Infant sleep is organised differently from adult sleep. Newborns cycle in shorter loops, spend a larger share of sleep in the active, REM-like state, and need frequent feeding, so they surface often (Mirmiran et al., 2003, Sleep Medicine Reviews). A systematic review of observational studies describes how total sleep and the length of the longest stretch change gradually across the first year as the body clock matures (Galland et al., 2012, Sleep Medicine Reviews). Waking every couple of hours in the early weeks is typical development, not a problem to be solved.
The second is you. Research comparing postpartum women with non-postpartum women has found that new mothers sleep less and have more fragmented sleep, and that this is linked to poorer daytime alertness and performance (Insana et al., 2013, Sleep). A study of new mothers and fathers found that both parents’ sleep is disrupted in the early months, with mothers typically more affected (Gay et al., 2004, Biological Research for Nursing). Even after the baby settles, many parents find they keep waking on the old schedule, because the body has learned to be light and watchful. If this sounds familiar, postpartum insomnia explains why you can lie awake even when the baby is asleep.
The practical takeaway is gentler than it sounds. You are not failing to sleep properly. You are sleeping in short segments because your nights are being cut into short segments, and the aim is to protect one longer stretch where you can. How to split night shifts with a partner shows one way to do that.
Why do I wake more between cycles in perimenopause?
In perimenopause, the cycle boundaries themselves haven’t changed, but the threshold for waking has. Sleep difficulty is one of the most common complaints of the menopausal transition, and a review of the evidence describes disrupted sleep as frequent and often persistent during this stage (Baker et al., 2018, Nature and Science of Sleep). A large community survey also found that sleep difficulty rises as women move through the transition (Kravitz et al., 2003, Menopause).
Several things can stack up. Fluctuating oestrogen and progesterone affect the systems that regulate temperature and arousal. Night sweats can pull you out of sleep, and the alertness that follows can last a long while after the heat has passed, as we describe in night sweats and sleep. Many women also notice they wake in the small hours and find it hard to settle again, a pattern explored in why you wake at 3am. The broader picture is in perimenopause and sleep.
What actually helps you fall back asleep after a cycle ends?
Because the waking itself is normal, the useful goal is making the return to sleep easier. A few things that tend to help:
- Keep the room cool and dark. Core body temperature needs to fall for sleep to deepen, so a cooler room helps at every cycle boundary, and matters even more if you have night sweats.
- Leave the clock alone. Checking the time turns a harmless arousal into a small problem-solving task, and that alertness is what keeps you up.
- Stay low-key when you wake. Dim light, slow breathing and no phone give your brain the signal that nothing needs attention.
- Keep a steady wake time. A consistent rising time anchors your body clock so that cycles line up more predictably.
If you do find yourself wide awake, how to get back to sleep has a calm, step-by-step approach.
When is waking at night worth mentioning to a clinician?
Occasional waking is part of being a sleeper. It is worth raising with a doctor if you regularly lie awake for long stretches, if you wake gasping or with loud snoring, if you feel unrefreshed on most days for several weeks, or if low mood or anxiety is building. These can point to something treatable, such as sleep apnoea, thyroid changes or low iron, and a clinician can look into them properly. Nothing here is a reason to worry in the meantime; it is simply information worth having.
The calm version
Your sleep was never meant to be one unbroken block. It is a series of cycles, and brief waking between them is expected. For new parents and women in perimenopause the gaps are simply easier to notice, and harder to cross back over. Mendtide reads your Apple Health sleep data and turns it into a calm morning briefing, so you can see the shape of your nights without a score to chase. It won’t diagnose anything, but it can help you notice patterns worth bringing to a clinician.
Waking between cycles is part of how sleep works. Be patient with the gaps, and protect the stretches around them.