Regular bedtimes linked to stabler blood sugar, study of 227,000 nights finds
Adults who maintain consistent sleep timing show measurably lower overnight glucose variability than those with irregular bedtimes, according to a preprint that draws on one of the largest wearable datasets assembled to date on the subject.
Researchers analysed 227,860 nights of paired sleep and continuous glucose data from 5,849 adults, using the Ultrahuman AIR smart ring and Ultrahuman M1 continuous glucose monitor. Participants were otherwise healthy and living normally outside clinical settings.
The effect is also evident in related research. Adults sleeping four to five hours showed glucose variability 2.87 percentage points higher than those sleeping eight hours. Persistently late bedtimes were associated with a 1.18 percentage-point increase in glycaemic variability, and short sleepers spent 3.11 percentage points less time with glucose in the healthy range of 3.9 to 10 mmol/L.
Clustering analysis identified distinct sleep-metabolic phenotypes within the dataset. Participants with poorer metabolic profiles also showed stronger coupling between heart-rate patterns and glucose curves overnight, suggesting cardiovascular and metabolic dynamics during sleep are more tightly linked than generally recognised in healthy adults.
Overnight glucose regulation depends on circadian rhythms and autonomic nervous system activity working in concert. Irregular sleep timing disrupts both. The authors propose sleep-wake regularity as a simple behavioural marker of cardiometabolic stability — one that is already captured passively by most consumer wearables.
The study is a preprint posted on medRxiv on 4 March 2026 and has not yet been peer reviewed. The participant pool was drawn from Ultrahuman device users, who may not be representative of the broader population. The findings establish an association rather than causation.
Source: Dhawale N., Gandhi D., Shanmugam A., et al. Sleep consistency is a low-cost, reliable indicator of nocturnal glycemic control: observations from 227,860 nights of real-world smart-ring and continuous glucose monitoring data. medRxiv preprint, 4 March 2026. DOI: 10.64898/2026.03.04.26347496.
This article is part of the site’s sports science reference for endurance athletes.
Last Updated on 3 October 2026 by tfk the5krunner
Small things I always use
- Garmin 90-degree charging adapter: Charges your Garmin from any USB-C cable. Essential when travelling. I use one.
- Body Glide: The blue anti-chafe stick swimmers and runners carry. I use it.
- Speedo earplugs: Fewer ear infections and no cold-water dizziness. I use them.
- Dryrobe Advance: My winter changing robe for open-water swims. I use one. A cheaper option is the AONYIYI changing robe.
- Maurten: Race fuel that stays easy on the stomach. I use them.
- Beet It Sport nitrate shots: Beetroot shots I take in the days before a race. I use them.
- Garmin charging puck: The quickest way to top up before a session. I use one.
- Injinji: Toe socks that stop rubbing, so you run more. I use them.
- Ultimate toe protectors: Stop black toenails on long runs. They work. I use them.
- Compressport R2 v2 calf sleeves: My calf sleeves of choice. I use them.
- Cellucor C4: My pre-workout before hard sessions.
- TPU tubes: Schwalbe Aerothan, Tubolito and Pirelli SmarTube. Light, tiny spares. I use all three.
- G8 insoles: Adjustable insoles that are good. I use them.
- Cycplus Cube: A 97g electric pump that gets a road tyre rideable in two minutes. I carry one. 5% off with code THE5KRUNNER.
Watches and sensors
- Polar H10: My daily driver for waking HRV.
- Polar Verity Sense: My backup arm-worn HR sensor.
- Nomad bedside charger: Charges my iPhone and Apple Watch overnight. I use it, and many of their bands.
- Train.Red: The best muscle oxygen sensor I’ve used.
- Tymewear: Accurate heart rate and reliable ventilatory zones. I use it to pace endurance rides over an hour.
- Garmin Forerunner 970: A pro-grade triathlon watch. I use this.
- Apple Watch Ultra 4: My daily smartwatch. No phone needed on rides.
- Garmin Fenix 9 Pro: I’ve just bought one.
On the bike
- Continental GP5000 for everyday riding, and Aero 111 on the front for special occasions.
- Helmets: Specialized S-Works Evade 3 for road riding, and Rudy Project Wing for TT-style races. I use both.
- Ravemen FR300: A front light that mounts under your Garmin or Wahoo. I use one.
- Wahoo TRACKR Radar: I use it on one bike and Varia on the other. They perform the same.
- Garmin Varia RTL515: Radar that warns you of cars from behind. I use this model.
- Wahoo ELEMNT Roam 3: The bike computer that’s easy to use. I use mine on most rides.
- Favero Assioma Pro RS2: Accurate power pedals that swap easily between bikes. I use this model.
Home and indoor training
- NPE Runn: Makes my basic treadmill smart, sending more accurate speed and distance to my watch and Zwift. I use it.
- Google Wifi: Keeps Zwift connected in my pain cave. I use it.
- Apple TV 4K: Zwift on the big screen. I use two.
- Google Nest Doorbell (wired, 2nd gen): My video doorbell, running in both Google Home and Apple Home. I use it.
Health, recovery and sleep
- FreeStyle Libre 3 Plus: Shows how my blood sugar responds to diet.
- hDrop: Measures my sweat loss in summer and indoors.
- Fourth Frontier Zone: Checks my heart under load in hard sessions.
- Oura Ring 5: My partner’s recovery tracker of choice.
- Eight Sleep: A cooling mattress cover my partner and I use nightly.
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tfk is the founder and author of the5krunner, an independent endurance sports technology publication. With 20 years of hands-on testing of GPS watches and wearables, and competing in triathlons at an international age-group level, tfk provides in-depth expert analysis of fitness technology for serious athletes and endurance sport competitors. See the gear tfk uses. ID
