What Is Sleep?
Sleep is an active, structured process of different stages that your body moves through several times a night, cycling between lighter and deeper stages and periods of dreaming. Each cycle does different work: repairing the body, consolidating memory, balancing hormones, and resetting you for the day ahead.
Theia brings your sleep together from your connected wearable and organizes it into a few views:
Sleep stages show how your night was divided between Light, Deep, REM, and Awake
Last night covers how much you actually slept, how long you were in bed, and time spent awake
Sleep timing shows when you slept, not just how long
Together these help your care team see both the quantity and the shape of your sleep.
The Four Sleep Stages
Over a typical night, sleep moves through four stages, each supporting your body in a different way. The ranges below are typical for healthy adults - your own night will look different, and a single night outside these ranges is rarely cause for concern.
Light sleep (40-60%): The bridge between being awake and deeper sleep. Your muscles relax, heart rate slows, and body temperature drops. Light sleep supports memory and learning, and most adults spend about half the night here.
Deep Sleep (13-23%): The most physically restorative stage. This is when your body handles repair, immune support, and solidifying what you learned during the day. Deep sleep is usually strongest early in the night.
REM Sleep (20-25%): When most dreaming happens. Your brain stays active, processing emotions and locking in skills and spatial memory. REM stretches get longer toward morning.
Awake (<10%): Short wake-ups between cycles are completely normal and easy to miss. most adults spend under 10% of the night awake. More frequent wale-ups can leave you feeling less rested even when your total sleep looks fine.
Why Sleep Matters
It's easy to think of sleep as simply "rest," but it's one of the most powerful levers for metabolic health specifically. The American Diabetes Association now places healthy sleep alongside nutrition and physical activity as a core lifestyle factor in preventing and managing type 2 diabetes. This is sleep across three dimensions: quantity, quality, and timing. Here's how it connects to the same systems tracked elsewhere in Theia:
Insulin Sensitivity: Short and poor-quality sleep are linked to reduced insulin sensitivity, as well as associated with a higher risk of developing type 2 diabetes.
Next-Day Glucose: Because of that drop in insulin sensitivity, poorer or shorter sleep tends to show up as higher glucose readings in the following day, including after meals.
Appetite & Cravings: Short sleep shifts the hormones that govern hunger and fullness, which can increase appetite and cravings, especially for quick-energy, high-carb foods that drive larger glucose swings.
The Daily Rhythm: Sleep, meals, movements, and morning glucose all run on the same 24-hour clock. Not just how much you sleep, but when you sleep is apart of the rhythm too. A more irregular sleep pattern is independently associated with higher metabolic risk.
Sleep Timing: When you sleep, Not Just How Long
Duration vs. Timing: Duration is how long you slept. Timing is when. Eight hours from 2AM to 10AM is not the same night, biologically, as eight hours from 10PM to 6AM - even though the total is identical.
Why Timing Matters: When you sleep is part of the same daily rhythm as your meals, movement, and morning glucose. A more regular bedtime and wake time can make all of those patterns easier to read. Consistency, not just total hours, is increasingly recognized as its own pillar of sleep.
What the Research and Guidelines Say
It helps to know where commons sleep targets come from.
The 7-9 hour recommendation. The most widely used sleep target for adults comes from the National Sleep Foundation, whose expert panel reviewed the scientific literature and recomments 7-9 hours of sleep per night for most adults (7-8 hours for adults 65+). This is the range Theia uses as a reference
A few things make this more useful than a single magic number:
The range is the point. Individual needs vary within 7-9 hours, and the relationship isn't "more is always better." A meta-analysis of prospective studies found the lowest type 2 diabetes risk around 7-8 hours, with risk rising for bother shorter and longer sleep. The goal is finding where you feel and function best, not hitting an exact figure.
Consistency counts as much as quantity. In Theia, consistency measures how often you meet your sleep duration goal.
Quality matters alongside duration. Frequent wake-ups or very little deep or REM sleep can leave you less rested even when total hours look fine.
At Theia, your goals are personal. These guidelines are general reference points, not personalized prescriptions. The right sleep target depends on your health, history, and goals. Instead, patients and providers set targets together, and Theia tracks consistency against them.
Haven't set goals yet? Visit the Goals page within Theia to set nutrition, activity, and sleep goals.
Accuracy & Limits
From your wearable. Stages and timings come from your connected device or a sleep session you logged. Theia brings them together in once place for you and your care team.
Stage names can differ. Devices name and detect sleep stages differently. Where we can, we map them to Deep, REM, Light, and Awake.
Insight, not diagnosis. Use Sleep to understand your nights and to share what you notice with your care team. Wearable data is not a diagnosis. If something concerns you, check in with your provider.
Need Help?
Our team is always glad to assist if you have any questions about your account.
Our support team can be reached via [email protected] or you may send us a message via the Help button in the Theia app.