Yes. Prediabetes is associated with changes in sleep architecture — including a reduction of approximately 6 minutes of REM sleep per night and a higher likelihood of fragmented, unrefreshing sleep. 62% of adults with prediabetic glucose levels report poor sleep, compared to 46% with normal glucose. The relationship runs in both directions: short or disrupted […]
Yes. Insulin resistance suppresses slow-wave sleep — the deepest and primary restorative stage — without necessarily reducing total sleep time. A 2008 crossover study found that selectively suppressing slow-wave sleep for three nights reduced insulin sensitivity by 23% in healthy adults, with a correlation of r = 0.89 between slow-wave sleep loss and insulin sensitivity
“Adrenal fatigue” is not a recognized endocrine condition, but the 3am waking pattern it describes is documented and measurable. The research identifies two distinct HPA axis states that produce different sleep disruption patterns: hyperactivation (elevated nocturnal cortisol, associated with accumulated stress) and hypoactivation (blunted cortisol response, associated with prolonged psychological burden). These are opposite ends
Yes. Caloric restriction elevates cortisol — the body’s primary stress hormone — which delays the overnight cortisol nadir, increases the number of nocturnal awakenings, and reduces slow-wave sleep. The effect is dose-dependent: moderate restriction raises cortisol modestly, while fasting-level deficits produce larger and more consistent elevations. Sleep extension may offset some of the metabolic cost
Cortisol rises during the second half of the night as part of the circadian rhythm, preparing the body for waking. When that rise comes too early, too steeply, or from a dysregulated baseline, it activates the brain’s arousal circuits and produces a 3am waking — often with racing thoughts, a sense of unease, or a
Waking up hungry at 3am is driven by two overlapping mechanisms: a blood sugar drop that triggers stress hormones and hunger, and a disruption in the hormones that regulate appetite — leptin (which suppresses hunger) and ghrelin (which drives it). Sleep restriction suppresses leptin and elevates ghrelin, creating a hormonal environment where hunger fires during
Yes. When blood glucose drops below approximately 70 mg/dL during sleep, the body releases epinephrine, cortisol, and glucagon to raise it back up. These same stress hormones activate the brain, producing the experience of waking abruptly — often between 2 and 4am — with a racing heart, sweating, or sudden alertness. This counterregulatory response occurs
How you sleep is tied to memory, mood, blood pressure, blood sugar, and whether you can show up for the people and activities that matter to you. For years, though, the tools we’ve had to measure sleep and long-term health risk have been fairly blunt: “how many hours,” questionnaires, or a diagnosis like sleep apnea.
Now something new is arriving: large AI models that look at every second of your sleep study and try to map that pattern to future health. One of the latest examples is the 2026 project, SleepFM—developed by a multi-institution collaboration including researchers at Stanford & Harvard.
SleepFM is a “foundation model” trained on more than half a million hours of clinical polysomnography (full overnight sleep studies with EEG, breathing, heart rhythm, and more).
From one overnight sleep study, it can estimate risk for conditions ranging from dementia to heart failure and all-cause mortality.
At the same time, other human studies are sharpening the picture of which features of sleep matter most in later life: how much deep slow-wave sleep you get, how stable your emotional brain feels after sleep, and how “old” or “young” your brain looks.
In this article, we’ll cover:
How the 2026 SleepFM study uses one overnight sleep study to predict risk for about 130 conditions, including dementia and cardiovascular disease.
What new work in older adults shows about deep non-REM slow-wave sleep and anxiety, and why that matters for brain aging..
How slow-wave sleep loss over years relates to your chance of developing dementia in late life.
How deep-learning models that estimate your “sleep age” from overnight studies connect to life expectancy.
All of this will stay grounded in what you can actually do with this knowledge: how to think about getting a sleep study, how to protect the parts of sleep that seem most tightly linked to brain and heart health, and how to view these new AI tools in a measured helpful way.
Let’s get started.
Overview: Estrogen, progesterone, and their downstream metabolites regulate multiple pathways that govern sleep — from the brain’s inhibitory tone to body temperature to the neurotransmitters that set the sleep-wake cycle. As these hormones’ function is disrupted during perimenopause and menopause, each pathway is affected in a specific way: Progesterone is converted to allopregnanolone, a neurosteroid
Testosterone, growth hormone, and DHEA all decline as men age — starting as early as the late 20s and accelerating after 40. These hormonal changes don’t reduce sex drive and muscle mass alone; they directly alter the brain’s ability to produce and maintain deep sleep. Declining testosterone function involves three concurrent changes: falling production from
