Why does anticipatory stress disrupt sleep if no call actually comes?

The nervous system cannot distinguish between a threat that arrives and one that might arrive. When the brain registers that a demand could land at any moment, it maintains a state of partial alertness — lighter sleep stages, more frequent micro-arousals, a lower threshold for full waking. This is the same sympathetic activation pattern that underlies other forms of anticipatory anxiety. The body is not irrational; it is simply responding to an unresolved open loop.

Does this affect only workers in healthcare or emergency services?

No. The research applies to any worker in an on-call arrangement — from retail shift workers receiving late-night roster changes, to corporate managers expected to respond to international time zones, to community services workers carrying emergency phones. The mechanism is the psychological state created by unresolved availability expectations, not the industry or profession.

On-call and can't sleep: the anticipatory anxiety mechanism

What just happened

CQUniversity researchers Madeline Sprajcer and Grace Vincent published a piece in The Conversation today explaining a phenomenon that a lot of people in on-call work arrangements have experienced but may not have seen named precisely: you cannot sleep even when the call never comes.

Their research, published in Sleep Health, found that just knowing you might be called in is enough to disrupt sleep. The call does not need to arrive. The interruption does not need to happen. The nervous system’s response to unresolved availability — the open loop of I might be needed at any moment — is sufficient to alter sleep architecture in measurable ways: lighter sleep stages, more frequent micro-arousals, reduced total sleep time, higher fatigue the next day.

For anyone who has spent a night with a work phone face-up on the bedside table and woken exhausted despite an undisturbed night: this is the mechanism.

Both-and

The biology underneath

Sleep is not a passive state. Restorative sleep — the kind that actually repairs tissue, consolidates memory, regulates cortisol, and restores immune function — requires the nervous system to genuinely downshift. The transition from waking to deep sleep involves a handover from sympathetic to parasympathetic dominance: heart rate slows, breathing deepens, muscle tone drops, the stress-response machinery stands down.

That handover cannot happen fully when the brain has an unresolved open loop. A phone that might ring. A message that might come. A situation that might require a response. The research describes this as the nervous system maintaining a state of readiness that is structurally incompatible with deep sleep — not because you are consciously thinking about work, but because the vigilance state persists below conscious awareness.

This is why the finding that calls that never come still disrupt sleep is not surprising from a biological standpoint, even if it sounds counterintuitive. The nervous system is responding to an unresolved threat, and the absence of the threat’s arrival does not resolve it. The loop closes only when the on-call period ends.

Who this affects and how broadly

On-call arrangements span industries in ways that are easy to underestimate. Healthcare workers and emergency services are the obvious examples — but the same pattern applies to: retail and hospitality workers receiving last-minute roster changes by text; corporate and financial sector workers expected to be reachable across international time zones; community and disability service workers carrying emergency phones; managers who are never formally on call but have implicitly been expected to respond for long enough that the expectation has become internalised.

The right-to-disconnect legislation that passed in Australia in 2024 was a meaningful step — it created a legal framework for employees to disengage from unreasonable contact outside working hours. But the legislation explicitly excludes on-call arrangements. If your role involves a formal on-call obligation, the disconnect right does not apply. Schedule design is the primary lever remaining.

The perimenopausal complication

For women in their forties and fifties, on-call sleep disruption lands on terrain that is already compromised. Perimenopause is associated with changes in sleep architecture independent of work — increased sleep fragmentation, reduced slow-wave sleep, heightened sensitivity to nocturnal arousal. The physiological changes of the perimenopause shift the nervous system’s baseline in ways that make it harder to sustain deep sleep in response to any additional stressor.

An on-call obligation in this context does not add a sleep disruption to a normal baseline — it adds it to a baseline that is already more fragile. The cumulative effect on daytime functioning, cognitive performance, mood regulation, and metabolic health can be substantial, and it is the kind of compounding harm that tends not to get identified clearly in either occupational health assessments or routine GP consultations.

If you are in perimenopause and in an on-call role and you are struggling with sleep: both things are contributing, and naming both matters for addressing either.

What the research says about what helps

The CQUniversity researchers are clear that individual strategies — earlier bedtimes before on-call nights, clear pre-sleep wind-down rituals, limiting screens in the hour before bed — can reduce the impact. These are real and worth doing.

They are also clear that the weight of responsibility sits with organisations, not individuals. Sustainable on-call scheduling — predictable rotations, sufficient recovery time between on-call periods, rotation among a large enough pool of workers that no single person carries the obligation too frequently — is the intervention that changes the population-level harm, not individual sleep hygiene advice.

The person who designs the on-call schedule is making decisions that directly affect the sleep architecture of everyone on it. That is not how it is typically framed in workplaces, but it is what the evidence describes.

My two cents

Sleep disruption is one of the most underestimated health exposures in working life — and anticipatory stress from on-call availability is one of the most undernamed causes of it. The thing that makes this research valuable is the precision: it is not about overwork, or long hours, or the stress of a demanding job in a generic sense. It is specifically about what happens when the nervous system cannot close a loop.

The clinical implication for anyone presenting with persistent fatigue, poor sleep quality, or unexplained mood disruption is worth checking: is there an on-call obligation in the picture? Not just formal rostered on-call, but the informal version — the expectation that you are reachable, the phone that never quite turns off.

The loop that cannot close at bedtime does not just cost you that night’s sleep. Over weeks and months, it compounds.

Verdict: yes — the mechanism is real, the population affected is larger than it looks, and naming it precisely is the first step toward doing something about it.

Sources cited

How being ‘on-call’ for work can disrupt your sleep — even if the call never comes. The Conversation, 21 August 2026. https://theconversation.com/how-being-on-call-for-work-can-disrupt-your-sleep-even-if-the-call-never-comes-286763