I used to be a great sleeper. I would get a full eight to 10 hours of sleep without any supplements, and not even the blasting morning sun could wake me up. Now, I have to use a sleep mask, take magnesium and keep my pillow at the perfect height to get decent sleep. All of these things help to some extent, but none of them fixed the consistent 3 a.m. wake-ups where I was drenched in sweat.

As someone who tests health gadgets for a living and a certified sleep coach, I became incredibly frustrated with my sleep hygiene. I thought I knew all the hacks and tried-and-true methods to get the best sleep. I attributed my constant wake-ups to a plethora of things, like stress, my partner’s body heat and the general weight of being a person with a full-time job while also trying to balance a social life and everything going on in the world.

What I hadn’t considered before was the role my hormones were playing. I know how deeply menopause affects sleep in older people, but as a 35-year-old, it hadn’t even crossed my mind that hormonal changes could be to blame. 

According to MIT Health, perimenopause, the hormonal transition that precedes menopause, can begin a decade before the last menstrual period, with symptoms manifesting in the mid- to late-thirties for many people. One of the earliest and most disruptive symptoms is what I was experiencing: fragmented and thermally unstable sleep.

With the current heat wave driving nighttime temperatures to record highs, getting a good night’s rest has felt practically impossible for everyone. But when you layer extreme summer weather on top of shifting hormones, “sleeping hot” takes on a whole new meaning.

Why you may be waking up at 3 a.m. drenched in sweat

Estrogen plays a direct role in thermoregulation. It’s the hormone that helps the hypothalamus, the brain region that regulates temperature and sleep, maintain what researchers call a thermoneutral zone. Essentially, it’s the margin within which core body temperature can shift without triggering a vasomotor response like night sweats (a common reaction during menopause or perimenopause, caused by a drop in estrogen levels) that wakes you up. As estrogen begins to fluctuate in perimenopause, that margin starts to narrow. 

“Those hormones fluctuate a ton during perimenopause, and they start to become more irregular,” says Dr. Nicole Moyen, who leads the clinical research team at sleep tech company Eight Sleep. “With that, the hormones and your body temperature in general also drive changes in the brain. And when estrogen starts to decline, we see changes in how that thermostat operates.”

A 2025 narrative review in the Journal of Clinical Medicine explains the process. The scientific explanation is that estrogen deprivation disrupts neurokinin B signaling in the hypothalamus, destabilizing the circuits that control temperature. The result is hot flashes, night sweats and even sudden chills that are more pronounced at night, when the body’s temperature is already cycling as part of normal sleep.

“Think of the thermostat in your house,” Moyen explains. “If it gets too hot, the AC kicks on. Our body’s AC is sweating and dilating our blood vessels (vasodilation) to cool us down.” During menopause, when estrogen levels drop, previously normal temperatures can feel too hot, leading to increased sweating. This is what’s known as a hot flash.

There’s also a timing aspect that explains why the worst thermal irregularities occur in the second half of the night. During REM sleep, the body’s temperature regulation system becomes impaired. “Your muscles are paralyzed during REM [sleep]. Your temperature regulation system is also essentially paralyzed,” Moyen says. 

For people in perimenopause, whose thermoneutral zone is already narrowed, the second half of the night can become the window of greatest risk of hot flashes and wake-ups.

Progesterone is a hormone produced primarily by the ovaries after ovulation, and it adds another layer to this for people with menstrual cycles. During a typical menstrual cycle, progesterone rises in the second half, which in turn raises core body temperature. As cycles become irregular during perimenopause, those progesterone fluctuations become unpredictable.

The question of whether perimenopause is identified and discussed early enough is something else to consider. 

“I think in the last couple of years it’s become more prominent, but what I haven’t seen is people defining what it is, how it’s diagnosed and how to have this conversation with your doctor,” says Moyen. 

Diagnosis is further complicated by the fact that hormone levels fluctuate significantly during perimenopause, so a single blood test cannot confirm the transition. Moyen explains that clinical assessments rely primarily on self-reported symptoms, which require people to closely monitor their bodies to recognize changes and be confident enough to bring them up with their healthcare provider.

That attunement, for me, came through all the data I’ve collected over the years. As someone who has professionally tested sleep and fitness trackers, I have a wealth of data on my sleep. But that data only tells me what’s happening, not why, and it certainly cannot change my body temperature while I’m sleeping to prevent hot flashes. 

What intrigued me about the Eight Sleep Pod 5 Core is that it adjusts its temperature to influence your body temperature in real time while you sleep. As someone experiencing perimenopause, this is my experience with the device.

What is the Eight Sleep Pod 5 Core?

The Eight Sleep Pod 5 is a mattress cover that uses a water system to cool or warm your bed. It has a bedside hub that circulates temperature-controlled fluid through tubes embedded in the cover, keeping each side of the bed at independently set temperatures.

In the Eight Sleep app, the temperature is displayed on a sliding scale from -10 to +10, where 0 is a neutral baseline and each level represents roughly a 2.75-degree Fahrenheit adjustment. Ranging from 55 to 110 degrees Fahrenheit, the Eight Sleep temperature scale is as follows:

• Cooling (-1 to -10): Ranges from slightly cool down to a minimum of 55 degrees Fahrenheit.
• Neutral (0): Baseline temperature, usually around 70 to 90 degrees Fahrenheit, depending on the ambient room temperature.
• Heating (+1 to +10): Ranges from slightly warm up to a maximum of 110 degrees Fahrenheit.

Being able to drop the temperature on my bed to 55 degrees is a game changer during the summer heat, especially if your bedroom’s AC is struggling to keep up. My partner also runs warm, so it’s nice that we can both set our sides of the bed to our ideal temperature. I keep my side between  -2 and -4, while he keeps his a few degrees higher. 

The system’s intelligence lives in the Autopilot feature, which tracks sleep stages in real time through sensors embedded in the cover and adjusts your bed’s temperature while you sleep. The Pod also serves as a wearable-free sleep tracker with the Autopilot 4.0 feature, which integrates with Apple Health and Google Health Connect. The Pod tracks heart rate, heart rate variability, respiratory rate, sleep stages and snoring.

I tested the Eight Sleep Pod for 60 days. Here’s how my deep sleep changed

The first few nights testing the Pod 5, I actually got worse sleep than before. I woke up with my hands and feet pretty cold. I had set my Pod too cool, and would wake up having to adjust it a little warmer. It took me a few nights of trial and error to get the temperature just right. Within the first week, I found the temperature that works best for me. It wasn’t until week two that I started to see improvements.

I started sleeping on the Pod in late April. Since then, I’ve been keeping a close eye on the data using my Oura Ring. 

For the first 30 days, my average deep sleep was 1 hour and 8 minutes, or roughly 17% of my total time asleep. By June, as outside temperatures soared during a summer heat wave, that time had increased to 1 hour and 22 minutes, or 19% of my total sleep. Looking back at my Oura Ring data before using the Eight Sleep Pod, I see that I averaged 1 hour and 4 minutes of deep sleep. While the two devices use different technology and are not totally comparable, the data gives me insight into where I started. 

By June, my Oura Ring also showed an improvement in my sleep score, from 75 to 80, further confirming that my deep sleep has improved since using the Eight Sleep Pod. My REM sleep remained stable at 1 hour and 52 minutes across both months. Deep sleep is one of the stages most sensitive to thermal disruption. A 14-minute average monthly gain is a meaningful signal.

In the second half of my menstrual cycle, when progesterone elevates and core body temperature rises, the Pod 5’s autopilot adjusted my side of the bed more than it did during the first half of my cycle. My typical setting runs around -2. One night, I woke to find the system had dropped to -4 without my intervention. My body needed more thermal intervention than baseline, and the Pod responded before I was even aware of it.

Can a mattress cover actually reduce hot flashes? What the research says

Eight Sleep conducted a 2026 study on the Pod’s efficacy for people in menopausal transition. In a study of 98 peri- and post-menopausal people — with 35 of them taking hormonal replacement therapy (HRT) — sleeping on the Pod reduced nighttime hot flashes by an average of 56%, independent of taking HRT or menopausal phase. 

Moyen explains that the Pod keeps people within that narrowed thermoneutral zone just enough so that the body doesn’t trigger a vasomotor event.

The Pod also has a feature called Hot Flash Mode, designed to provide on-demand, rapid cooling for people who wake up with night sweats. “We designed it from a scientific perspective of how quickly it needs to cool, how long a hot flash lasts and then how much rewarming people want to help them fall back asleep,” Moyen says. The feature is triggered manually, either by tapping the buttons on the cover’s side or via the app.

How much does the Eight Sleep Pod 5 cost?

The Pod 5 Core is a significant financial commitment at $2,749 for a queen-size setup, with an optional Autopilot subscription starting at $199 per year. In my opinion, the subscription is not optional. Without it, the system’s adaptive intelligence is disabled, leaving a temperature-controlled pad without the automatic temperature adjustments that define the product’s value.

The deepest discounts of the year have been during Memorial Day and Black Friday, with up to $500 off the Core.

Why so many people are left in the dark when transitioning into menopause

When I mentioned to Moyen that my mother had no awareness of perimenopause as a distinct phase, that her frame of reference was simply losing her period, experiencing hot flashes and arriving at menopause, Moyen was unsurprised. 

“A lot of [people] don’t even know the difference between perimenopause and postmenopause,” she says. “Clinically, postmenopause is defined as 12 consecutive months without a period.” In theory, you could go 11 months without a period, have one, and you’d still be in perimenopause. The gap lies in how rarely this information reaches people with enough clarity to be useful.

At 35, I’m working without a formal diagnosis, even after visiting my ob-gyn yearly. What I do have is years of sleep data and anecdotal experiences that make it impossible to deny what is happening.

For people who have exhausted traditional explanations and remedies and are still waking up at 3 a.m. without a clear cause, the answer may be hormonal. It’s worth tracking more precisely, raising the concern with your doctor and understanding that the perimenopause transition often begins well before the medical system tells you it’s happening.