What is WASO and why does it matter for staying asleep?

WASO stands for Wake After Sleep Onset — the total minutes you spend awake after first falling asleep. It's the gold-standard metric researchers use to measure how well you stay asleep. Healthy adults usually have under 30 minutes of WASO. Consistently over 45 minutes is considered a red flag for sleep maintenance issues.

Does melatonin help you stay asleep?

No — immediate-release melatonin (the most common drugstore form) shows no significant effect on WASO in meta-analysis. The 2022 Menczel Schrire meta-analysis of randomized controlled trials confirmed this. Melatonin can help with sleep onset and shift work, but if your problem is waking up at 3am, standard melatonin is not the right tool.

What supplement actually helps you stay asleep?

Ashwagandha (typically 600mg/day) has the strongest evidence for reducing WASO. A 2021 meta-analysis (Cheah et al., 5 RCTs, ~400 participants) found a significant reduction in nighttime waking with a standardized mean difference of −0.39. Glycine (3g) also has supporting PSG-measured evidence from a small trial. Magnesium and L-theanine have weaker, more mixed evidence.

Why does alcohol make me wake up at night?

Alcohol is sedating in the first half of the night but as it metabolizes, it causes rebound arousal and fragments your sleep in the second half. The Jackson Heart Study (Spadola 2019, n=785) using actigraphy confirmed this fragmentation pattern. Most people fall asleep faster after drinking but wake up more often — and feel less rested in the morning.

How much does caffeine affect nighttime waking?

Caffeine adds about 12 minutes of WASO on average, according to a 2023 meta-analysis of 24 studies (Gardiner et al.). The effect persists much longer than people realize — caffeine consumed even 6-8 hours before bed can measurably increase nighttime waking, depending on dose and individual metabolism.

What's the ideal bedroom temperature for staying asleep?

Research consistently supports a bedroom temperature range of 20–25°C (68–77°F) for minimizing WASO. Temperatures outside this range — both too hot and too cold — significantly increase nighttime waking. Most sleep specialists recommend the cooler end (18–22°C / 64–72°F) for optimal sleep maintenance.

Is it bad to sleep with even a little light on?

Yes. The Cho 2016 study using polysomnography showed that even dim light at night — just 5–10 lux, roughly the level of a hallway nightlight bleeding under your door — significantly increased WASO and disrupted REM sleep. Your bedroom needs to be genuinely dark, not just 'kinda dark.' Blackout curtains and removing or covering LED lights helps.

Why do I keep waking up at 3am?

Waking up in the early morning hours is often driven by alcohol metabolism (if you drank in the evening), elevated cortisol from chronic stress, blood sugar swings from late-night eating, hot flashes (in perimenopausal/menopausal women), nocturia, or undiagnosed sleep apnea. The Vgontzas 2001 study showed chronic insomniacs have elevated cortisol particularly in the first half of the night. If 3am waking is consistent and unexplained, it's worth ruling out sleep apnea with a doctor.

How to Stay Asleep All Night: 31 Factors Ranked by Evidence (2026)

Ryan - Kygo Health
1 day ago
7 min read

You fall asleep fine. Then 3am hits and you're staring at the ceiling, doing math on how much sleep you'll get if you fall back asleep right now.

Person sleeping in a wooden bed with a blue blanket, clock showing 10:10 on nightstand, moon above. Peaceful night setting. Representing Kygo Healths 27 factors to stay asleep ranked by evidence.

Staying asleep is a different problem than falling asleep. The metric sleep researchers care about is WASO (Wake After Sleep Onset) — total minutes you spend awake after first falling asleep. The fewer the better.

We pulled 40+ studies and ranked 31 factors that actually move WASO. Some confirm what you'd expect (alcohol, caffeine, hot bedrooms). Others probably won't (immediate-release melatonin does basically nothing for staying asleep).

If you want to see how your own habits map to your nighttime waking, Kygo connects your wearable's sleep data with what you eat and drink so you can spot the actual triggers.

Download Kygo on iOS → Download Kygo on Android →

What "staying asleep" actually means

Quick definitions so the tables make sense:

WASO (Wake After Sleep Onset) — Total minutes you're awake after first falling asleep. Healthy adults usually sit under 30 min. Over 45 min consistently is a red flag.
Sleep efficiency — Percentage of time in bed actually sleeping. 85%+ is good.
Arousals — Brief wake-ups (often <15 sec) you may not remember but show up on PSG and most wearables as restlessness.
PSG — Polysomnography. The gold-standard sleep lab measurement.
Fragmentation — How broken-up your sleep is, regardless of total time.

1. Nutrition

Factor	Impact	Key Info	Plain English	Evidence
Dietary Fiber	↓ Arousals	St-Onge 2016; n=26, PSG, controlled crossover	More fiber = fewer nighttime wake-ups	Strong
Sugar / Refined Carbs	↑ Arousals	St-Onge 2016; n=26, PSG, significant predictor	Sugar directly increased sleep arousals	Strong
Caffeine	↑ WASO +12 min	Gardiner 2023; meta-analysis, 24 studies	Caffeine adds ~12 min of nighttime waking	Strong
Alcohol	↑ Fragmentation	Spadola 2019; Jackson Heart Study, n=785, actigraphy	Sleep breaks apart as alcohol metabolizes	Strong
Late Eating (<1hr)	↑ WASO 2–2.6× odds	Crispim 2022; British J Nutrition, large n	Eating right before bed doubles wake-ups	Moderate
Tart Cherry Juice	↓ WASO ~17 min	Pigeon 2010; n=15, RCT crossover, insomnia	Cherry juice cut nighttime waking vs placebo	Moderate

The headline finding: the St-Onge 2016 study fed people a controlled diet for several days and measured their sleep with PSG. Higher fiber meant fewer arousals. Higher sugar meant more. Both effects were independent of each other.

Caffeine is more nuanced than "don't drink it after 2pm." The Gardiner 2023 meta-analysis (24 studies) found caffeine adds ~12 min of WASO on average, but the effect persists much longer than most people think — up to 8 hours in some studies depending on dose.

Alcohol gets the biggest mismatch between what people feel and what's actually happening. It knocks you out faster, then fragments the second half of your night as it metabolizes.

2. Supplements

Factor	Impact	Key Info	Plain English	Evidence
Melatonin (immediate-release)	↔ No WASO effect	Menczel Schrire 2022; meta-analysis of RCTs	Standard melatonin does NOT help you stay asleep	Strong
Ashwagandha (600mg)	↓ WASO, SMD −0.39	Cheah 2021; meta-analysis, 5 RCTs, n=400	Ashwagandha significantly reduced nighttime waking	Strong
Glycine (3g)	↓ WASO, faster SWS	Yamadera 2007; n=11, PSG, crossover	Glycine reduced waking and deepened sleep	Moderate
Magnesium (500mg)	↑ Sleep efficiency (elderly)	Abbasi 2012; RCT, n=46, 8-week, 65+	Improved efficiency but no direct WASO data	Limited
L-Theanine (200–450mg)	↔ Mixed WASO results	Systematic review 2025	Some maintenance benefit but inconsistent alone	Limited
Valerian Root	↔ No consistent benefit	Shinjyo 2020; meta-analysis, 60 studies, n=6,894	Subjective improvement only, no objective WASO change	Weak

The biggest myth on this list: immediate-release melatonin (the kind sold in every drugstore) does basically nothing to help you stay asleep. The 2022 meta-analysis is clear on this. It can help with sleep onset and shift work, but if your problem is waking up at 3am, you're throwing money at the wrong supplement.

Ashwagandha has the strongest WASO evidence of any supplement studied. The Cheah 2021 meta-analysis pulled three trials specifically on sleep maintenance and found a meaningful reduction in nighttime waking.

Valerian sells well, performs poorly when objectively measured. People feel like it works, but PSG and actigraphy don't show it.

3. Exercise

Factor	Impact	Key Info	Plain English	Evidence
Moderate Aerobic Exercise	↓ WASO ~10 min	Riedel 2024; meta-analysis of RCTs, insomnia	Regular cardio cuts ~10 min of nighttime waking	Strong
Resistance Training	↓ Sleep disturbance, ↑ efficiency	Kovacevic 2018; review, 13 studies, n=652	Strength training improved mid-sleep disturbance	Moderate
Yoga	↓ WASO ~56 min	Bu 2025; network meta-analysis, 22 RCTs	Large WASO reduction in insomnia patients	Low
Evening Moderate Exercise	↓ WASO	Dolezal 2017; review, 34 studies	Moderate evening exercise helps you stay asleep	Moderate
Vigorous Exercise ≤1hr Before Bed	↑ WASO risk	Stutz 2019; meta-analysis, 23 studies	Intense exercise right before bed may fragment sleep	Moderate

The "don't exercise at night" advice is half-wrong. Moderate evening exercise actually improves WASO. The problem is vigorous exercise within an hour of bed, especially if it's harder than what you're used to.

The yoga number (56 min WASO reduction) looks too good to be true and probably is. Small samples, lots of variation between studies. The effect is real, just likely smaller than the headline number suggests.

4. Environment

Factor	Impact	Key Info	Plain English	Evidence
Bedroom Temp (20–25°C / 68–77°F)	↓ WASO at optimal range	Multiple PSG studies	Too hot or cold increases nighttime waking	Strong
Light at Night (even dim)	↑ WASO	Cho 2016; n=23, PSG, 5–10 lux	Even nightlight-level light increases wake time	Strong
Noise (>50 dBA)	↑ WASO +30 min	Basner 2018; WHO review, 74 studies	Noise above 50 dB adds ~30 min of waking	Strong
CO₂ >1000 ppm (poor ventilation)	↑ Wake time +5 min	Kang 2024; n=36, field-lab, 3 levels	Stuffy bedroom air measurably fragments sleep	Moderate
Mattress (medium-firm)	↓ Most consistent WASO	Hu 2025; n=12, PSG, 3 firmness levels	Medium-firm gave most stable sleep	Limited

The underrated one: the Cho 2016 light study used just 5–10 lux during sleep — about the level of a hallway nightlight bleeding under your door. That was enough to significantly increase WASO. Your bedroom needs to be dark, not "kinda dark."

The CO₂ finding is newer and most people have never thought about it. Sleeping with the door closed in a small room with no airflow can push CO₂ above 1000 ppm overnight, and the Kang 2024 study showed measurable WASO increase at that level. Cracking the door or running a fan helps.

5. Demographics & Health

Factor	Impact	Key Info	Plain English	Evidence
Aging (30 → 60+)	↑ WASO ~10 min/decade	Ohayon 2004; meta-analysis, 65 studies, n=3,577	Each decade adds ~10 min of nighttime waking	Strong
Female Sex	↔ Paradox: complaints vs PSG	Ohayon 2004	Women report worse sleep but objectively sleep better	Strong
Menopause (hot flashes)	↑ WASO, 69% flashes → wake	Joffe 2013; PSG + GnRH model, n=29	Nighttime hot flashes are a major wake trigger	Strong
Obesity (BMI ≥30)	↑ WASO significantly	Zhao 2021; Sleep Heart Health Study, n=5,723	Higher WASO independently associated with obesity	Strong
Shift Work	↑ WASO, ↓ efficiency	Wickwire 2017; review, SWSD patients	Shift workers have more fragmented daytime sleep	Moderate
Nocturia (≥2 episodes)	↑ WASO +34 min	Fung 2017; SOF study, n=1,520	More bathroom trips = much more nighttime waking	Strong
Obstructive Sleep Apnea	↑ WASO with severity	Patel 2019; comprehensive PSG review	Each breathing event triggers arousal and waking	Strong
Chronic Pain	↑ WASO, large effect	Mathias 2018; meta-analysis, 37 studies, PSG	Pain significantly increases nighttime wake time	Strong
Psychological Stress	↑ WASO via cortisol	Vgontzas 2001; n=24, 24-hr cortisol + PSG	Stress hormones directly fragment sleep	Moderate

A few things worth pulling out:

The female sleep paradox: women consistently report worse sleep than men but objectively sleep better on PSG. Why this happens is still debated.

Nocturia is one of the most underestimated WASO drivers. Going from 0 to 3-4 bathroom trips a night adds 34+ min of WASO on average. If this is you, it's worth talking to a doctor about — common causes include evening fluid timing, certain medications, untreated sleep apnea (yes, really), and prostate issues in men.

OSA is the elephant in the room. If you're consistently waking up multiple times a night and snore, gasp, or wake up unrefreshed, get tested. Untreated sleep apnea fragments sleep proportional to severity and is linked to almost every chronic disease worth avoiding.

What to do with this list

If you're trying to fix nighttime waking, start with the highest-evidence factors that you can actually control:

Cut alcohol within 3 hours of bed — biggest WASO win for most people who drink
Drop caffeine after noon — half-life is longer than you think
Cool, dark, quiet bedroom — temp 18–22°C, blackout curtains, white noise if needed
Stop eating within ~2 hours of bed
Move your body during the day — moderate aerobic, not vigorous within an hour of bed

If those aren't enough, look at the demographic/health factors. Nocturia, untreated OSA, chronic pain, and menopause are all fixable with the right help.

Track what's actually waking you up

The hard part isn't knowing what might be affecting your sleep. It's figuring out what's affecting yours.

Kygo syncs your wearable (Oura, Apple Watch, Garmin, Fitbit, WHOOP) with your food, drinks, and supplement logs and surfaces correlations between what you do during the day and how fragmented your sleep is at night. Stop guessing. Start knowing.

Download Kygo on iOS → Download Kygo on Android →

Or explore the interactive Staying Asleep Factor Explorer →

Sources

Nutrition

St-Onge MP et al. (2016). J Clin Sleep Med. Link
Gardiner C et al. (2023). Sleep Med Rev. Link
Spadola CE et al. (2019). SLEEP. Link
Crispim CA et al. (2022). Br J Nutrition. Link
Pigeon WR et al. (2010). J Med Food. Link

Supplements

Menczel Schrire Z et al. (2022). Neuropsychopharmacology. Link
Cheah KL et al. (2021). PLoS ONE. Link
Yamadera W et al. (2007). Sleep Biol Rhythms. Link
Abbasi B et al. (2012). J Res Med Sci. Link
L-Theanine systematic review (2025). Nutritional Neuroscience. Link
Shinjyo N et al. (2020). J Evid-Based Integr Med. Link

Exercise

Riedel A et al. (2024). Sleep Med Rev. Link
Kovacevic A et al. (2018). Sleep Med Rev. Link
Bu ZJ et al. (2025). BMJ Evid-Based Med. Link
Dolezal BA et al. (2017). Adv Prev Med. Link
Stutz J et al. (2019). Sports Medicine. Link

Environment

Akiyama Y (2021). Japan Architectural Review. Link
Cho CH et al. (2016). Chronobiology Int. Link
Basner M et al. (2018). IJERPH. Link
Kang M et al. (2024). Building and Environment. Link
Hu X et al. (2025). Nat Sci Sleep. Link

Demographics & Health

Ohayon MM et al. (2004). SLEEP. Link
Joffe H et al. (2013). SLEEP. Link
Zhao M et al. (2021). Obesity. Link
Wickwire EM et al. (2017). Chest. Link
Fung CH et al. (2017). J Am Geriatr Soc. Link
Patel SR (2019). Annals of Internal Medicine. Link
Mathias JL et al. (2018). Sleep Medicine. Link
Vgontzas AN et al. (2001). J Clin Endocrinol Metab. Link

Disclaimer: Kygo Health LLC is a personal data aggregation and insights platform designed for informational purposes only. The information provided by Kygo, including correlations, patterns, and trends identified in your data, does not constitute medical advice, diagnosis, or treatment. Always consult a licensed healthcare provider with any questions regarding medical conditions.