Written by the Nuvirox Research Team
Key Points
- Substitute teachers frequently get same-day or night-before assignment calls, which research on schedule instability links to measurably worse sleep than even night-shift work.
- A large study of over 16,000 hourly workers found unpredictable scheduling was a stronger predictor of poor sleep than having a young child or working nights.
- The core problem isn't the teaching itself — it's the anticipatory vigilance of not knowing your schedule until hours before it starts.
Short answer: yes, and it's less about the classroom and more about the phone call. Substitute teachers are frequently notified of assignments the night before, early that morning, or mid-shift when another sub cancels. Research on schedule unpredictability in hourly and shift-based work — the closest available evidence base, since no study has isolated substitute teachers specifically — consistently finds that not knowing your schedule in advance is associated with worse sleep than even fixed night-shift work. The uncertainty itself appears to be the stressor.
Why does an unpredictable schedule affect sleep more than a hard schedule?
A fixed night shift, however punishing, lets your body adapt: you know when you'll sleep and when you won't. An unpredictable schedule prevents that adaptation entirely. Your body never gets a consistent enough cue to settle into a rhythm, and your mind stays partly on alert — checking the phone, wondering if today's the day you get called, or whether tomorrow's assignment will require a 5:30 a.m. wake-up or none at all.
This is sometimes described as anticipatory vigilance: a low-grade state of readiness that keeps the nervous system from fully powering down at night, even when nothing is actively happening. It's a similar mechanism to why on-call workers report worse sleep quality even on nights they're never actually called in.
Is this really different from other unpredictable jobs?
Not fundamentally — substitute teaching shares its core stressor with other on-call and short-notice work. What's somewhat distinct is the combination of high-notice cognitive demand (managing a classroom of students you may have never met, with lesson plans you didn't write) landing on almost no preparation time. Workers in more predictable jobs at least get days to mentally prepare for a demanding day; substitutes often get hours.
There's also a financial layer: many substitutes are paid only for days worked, so declining a late assignment because you're exhausted has a direct cost. That combination of income pressure and unpredictability compounds the sleep-disrupting effect beyond what either factor would cause alone.
This kind of anticipatory-vigilance pattern shows up across other unpredictable-schedule work too — it's part of why night-shift workers struggle even on a fixed schedule, and why catching up on lost sleep is harder than it sounds. Startup founders face a related version of this problem — see why founders can't seem to get enough sleep — though the driver there is an inability to detach rather than schedule notice itself.
What Human Studies Actually Show
The most directly relevant evidence comes from The Shift Project, a Harvard-based research initiative that surveyed more than 16,000 hourly service-sector workers. The study found that unstable and unpredictable schedules — short notice, on-call shifts, last-minute changes — were associated with worse sleep quality, more difficulty falling asleep, and more nighttime waking. Notably, the researchers compared this effect to two well-established predictors of poor sleep (having a preschool-age child, and working a regular night shift) and found unpredictable scheduling was a stronger predictor of poor sleep than either one.
A companion analysis from the same research group, published through the National Bureau of Economic Research and later peer-reviewed, found that workers receiving less than one week's notice of their schedule reported worse sleep than those given two or more weeks, and that exposure to multiple forms of instability (short notice, on-call shifts, cancelled shifts) compounded the risk. Around three-quarters of workers in the broader sample reported only fair or poor sleep quality to begin with, which is itself a useful honest caveat — a lot of hourly, schedule-unstable work involves poor sleep as a baseline, not a rare complication.
A separate, smaller study looking specifically at on-call work found something worth noting as a genuine counterweight: on-call status itself didn't significantly change objective sleep architecture (measured by in-home EEG) in most participants, even though people subjectively felt less refreshed on-call. The effect was more consistently a subjective one — feeling worse rested — than a fully measurable change in sleep structure for everyone. That doesn't erase the problem, but it's an honest nuance: the harm may be as much about daytime functioning and perceived rest as about a wrecked night of sleep.
What Sleep+ Restore Won't Do
Sleep+ Restore is formulated to support your body's ability to relax and settle into sleep — it isn't designed to eliminate the underlying cause of schedule-driven sleep disruption, which is structural and logistical, not physiological.
If your schedule genuinely changes night to night, no supplement replaces having a consistent pre-bed wind-down routine you can run regardless of what time you'll wake up, or negotiating more advance notice where that's possible.
If sleep problems persist most nights for more than a few weeks regardless of your schedule, or you're experiencing symptoms of anxiety or depression tied to income instability, talk to a doctor — chronic uncertainty-driven insomnia sometimes benefits from CBT-I, which is specifically designed for exactly this kind of sleep-onset difficulty.
What Actually Helps When Your Schedule Isn't Fixed
Anchor your wake time, not your bedtime. Sleep researchers generally find that a consistent wake-up time does more for circadian stability than a consistent bedtime, which is useful if your work start time varies but you can still choose when you get up on off days.
Build a portable wind-down routine — the same 15–20 minutes of low light and no screens before bed, whether you're going to bed at 9:30 for a 5:30 call time or 11 p.m. because tomorrow's open. Consistency in the routine itself, even without a consistent clock, gives your body a reliable cue.
Where possible, ask about advance-notice policies. The research is fairly clear that even modest gains in notice (one week versus a few days) measurably improve reported sleep quality — it's a reasonable ask to raise with a district or staffing coordinator, not just a personal coping strategy.
Frequently Asked Questions
Why do I feel more tired on my unpredictable sub days than on days I know I'm off?
This tracks with the research: anticipatory uncertainty (not knowing if you'll get called) is itself linked to worse sleep, independent of whether you actually end up working. Your nervous system stays partly on alert even on nights nothing happens.
Does it help to just say yes to every assignment so I stop worrying about missing income?
The research on schedule instability suggests the opposite might help more — workers with some control over accepting or declining shifts report better sleep than those who feel they have no choice. If financially possible, protecting a few reliably off nights each week may do more for sleep than maximizing every assignment.
Is caffeine timing a bigger issue for substitute teachers specifically?
It can be, because early or late call times shift when you're using caffeine to cope, sometimes late enough in the day to interfere with that night's sleep onset. Keeping a personal caffeine cutoff (roughly 8–10 hours before your intended bedtime) tends to help regardless of what time your shift ends.
FROM NUVIROX
Why we formulated Sleep+ Restore
We built Sleep+ Restore around the idea that healthy sleep onset and sleep quality are best supported through a research-informed combination of ingredients working together, rather than any single compound. The formula is designed to support your body's natural ability to relax and wind down at night — not to sedate you or force sleep chemically.
Every batch is backed by our 60-day money-back guarantee — long enough to actually evaluate whether it fits into your routine the way it's meant to.
Learn more about Sleep+ Restore →The Bottom Line
The core issue for substitute teachers isn't classroom stress — it's that a body and mind can't fully relax when there's no way to predict tomorrow's schedule. The research on schedule instability, drawn from the closest available comparable populations, points to unpredictability itself as one of the strongest sleep disruptors researchers have measured, ahead of night-shift work and having a young child. Anchoring what you can control — a consistent wake time, a portable wind-down routine, and honest conversations about advance notice — is the most evidence-grounded starting point.
References
- Schneider D, Harknett K. Losing sleep over work scheduling? The relationship between work schedules and sleep quality for service sector workers. SSM Popul Health. 2020. PMC7644775.
- The Shift Project. Consequences of routine work schedule instability for worker health and wellbeing. PMC7730535.
- Nagashima S, et al. Effects of night-time on-call work on heart rate variability before bed and sleep quality in visiting nurses. PubMed PMID: 29808432.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This article is for informational purposes only and is not a substitute for professional medical advice.