Around 3 or 4am your eyes open, your mind starts racing and sleep will not come back. In perimenopause these late-night awakenings become common, with or without hot flushes. Two mechanisms meet. Oestrogen, which falls and fluctuates during the transition, makes sleep lighter. Cortisol, the hormone that prepares the body to wake up, starts to rise in the second half of the night, just when that lighter sleep is easiest to break.
Lighter sleep during the transition
The Seattle Midlife Women's Health Study followed 286 women from 1990 to 2007, with symptom diaries filled in several times a year and hormone measurements in first-morning urine (Woods and Mitchell, 2010). Waking in the night was worse in the late transition and early postmenopause. It went hand in hand with lower oestrogen, higher FSH, hot flushes, low mood, anxiety and perceived stress. Waking too early in the morning was linked to age, hot flushes, mood and stress, with no link to the stage of the transition.
Hot flushes and night sweats wake women up, yet many also wake without them, thoughts racing, and cannot get back to sleep. Missing the usual bedtime is sometimes enough to stay awake until late in the night.
Cortisol rises in the early hours
Cortisol follows a rhythm of roughly 24 hours. At its lowest early in the night, it rises in waves during the second half of sleep and peaks around waking, a curve described in the first all-night measurements in healthy volunteers (Weitzman et al., 1971). This rise prepares the body for the day. When sleep is already light, it comes at the hour when a noise, a wave of heat or a passing thought is enough to wake you.
In perimenopause the stress system is also under more strain than before. Short nights, overly strict diets and long, draining workouts add stress to this background without giving anything back.
A menopause simulated in the lab
A Boston team reproduced two features of menopause in young women, broken sleep and a drop in oestradiol (Cohn et al., 2023). Twenty-two women spent five nights in hospital, two normal nights and then three nights in which their sleep was repeatedly interrupted. Fourteen of them repeated the study after a treatment that lowered their oestradiol to postmenopausal levels.
After the broken nights, bedtime cortisol was 27% higher, and the normal rise in cortisol in the half hour after waking was 57% smaller. The longer the time spent awake in the middle of the night, the stronger this disruption. Lower oestradiol had its own effect, with bedtime cortisol 22% lower. The authors conclude that each of the two independently disturbs the hormonal stress axis, and that fragmented nights may weigh on heart and metabolic health over the years. The study involved young women and only a few nights, so it remains a model of menopause.
Alcohol and the timing of dinner
Many women notice they tolerate alcohol less well at this stage. Beyond one glass, sleep almost always suffers, with waking in the night, often around 3am, and sometimes sweats. Over a week, the tiredness builds up.
The timing of the last meal matters too. A trial in Chicago followed 39 adults living with overweight, aged 36 to 75, for seven and a half weeks (Grimaldi et al., 2026). One group finished their last meal at least three hours before bed, which gave 13 to 16 hours without food overnight, compared with 11 to 13 hours in the control group. Both groups dimmed the lights three hours before sleep. With the earlier dinner, blood pressure dipped more at night, the heart beat more slowly and night-time cortisol was lower. The next morning, blood sugar rose less during a glucose tolerance test. Dinner was moved earlier, never skipped. The study is small, mixes men and women and did not measure early-morning waking. It still supports having dinner at a sensible time and then nothing until morning.
What helps broken nights, according to trials
A Belgian meta-analysis published in 2026 pooled randomised trials in perimenopausal and postmenopausal women with chronic insomnia (Bruyneel et al., 2026). Of 24 trials included, 17 could be combined. Drug-free approaches, cognitive behavioural therapy for insomnia, acupuncture, yoga and massage, improved sleep quality on both questionnaires used. Medicines worked on only one of the two. No treatment changed total sleep time. For the authors, cognitive therapy and techniques that calm an over-alert nervous system are the most robust first-line options.
Exercise alone is not always enough. In 1,579 postmenopausal women bothered by hot flushes, nine trials of physical activity did not clearly improve sleep quality or insomnia, with only a slight improvement in sleep problems (Corrêa et al., 2025). Hormone therapy, on the other hand, often improves sleep by calming hot flushes, and progesterone taken in the evening seems to help some women sleep better. This is a conversation to have with your GP.
When to see your GP
Waking almost every night for several weeks, tiredness that weighs on the day, a darkening mood or hot flushes that stop you sleeping are reasons to book an appointment. Loud snoring, pauses in breathing noticed by a partner or headaches on waking call for a check for sleep apnoea. Night-time palpitations, a thyroid problem or low iron can also hide behind broken nights.
This article is for information only and does not replace medical advice.