Building a sleep app for nurses, pilots, and the people who don't have a 9-to-5

A friend who works ICU nights asked me, in 2024, why none of her sleep apps understood what she was doing.

She’d open one of the popular ones, log a five-hour daytime sleep, and the app would politely tell her she’d had a poor night and should try going to bed earlier. The app meant well. Its model of a human was someone who sleeps at night. Her model of a human was a nurse who sleeps when the rotation allows.

That conversation was the start of AfterShift. This is what I learned building it.

Why is the 9-to-5 assumption everywhere in sleep apps?

Open any major consumer sleep app and walk through onboarding. You’ll be asked when you go to bed, when you wake up, and what your weekend pattern is. The app assumes a five-day workweek with weekends free, and it assumes “night” means one uninterrupted block of darkness.

Now take a typical nurse’s twelve-hour rotation: three days on, three days off, a two-week cycle, with days flipping to nights halfway through. Her sleep windows might be 10pm-6am one week and 9am-3pm the next, with a chaotic transition night in between. The sleep app’s model breaks, its recovery scores make no sense, and its caffeine recommendations actively harm her. (Most rosters like hers are variations on a handful of named patterns; rotating shift schedules explained lays out DuPont, 2-2-3 and the rest, and which are hardest on sleep.)

This is a real population. The US has about 4 million registered nurses, plus paramedics, firefighters, factory and logistics workers, airport ground crews, hotel and overnight staff, and a long tail of other people on rotating shifts or on call. Generic sleep apps serve none of them well.

What “shift-aware” means in practice

The first difference between AfterShift and generic apps is what counts as a sleep session. AfterShift accepts:

• A primary sleep block of any length, at any time of day, on any day.
• Naps before or after the primary block. Pre-shift naps are a recognised fatigue countermeasure for night work, and post-shift “anchor sleeps” before transitioning back to days are another. In AfterShift, naps count toward the sleep between your shifts.
• Fragmented patterns. A six-hour sleep broken once is structurally different from an unbroken six hours. With Premium, a Sleep Continuity card shows how broken each sleep was.

The second difference is the day itself. AfterShift measures from the end of one shift to the start of the next, not from midnight to midnight. Sleep debt, the Recovery Timeline, and the Readiness rating all work on that window.

Readiness is the part I’m proudest of. It answers one question: given the sleep you’ve had since your last shift, are you recovered enough for the next one? It compares the sleep inside that window with your sleep target and rates you Low, OK, or Good. Readiness is part of Premium, as are the Sleep Score and Shift Recovery Score for each sleep. The Shift Recovery Score weighs duration, continuity, and sleep stages.

Generic sleep apps tend to penalise the daytime sleep before a night shift because it doesn’t look like a night. AfterShift measures it against the window you actually had, which is the fair comparison for this user. Like every score in the app, Readiness is an informational rule of thumb and hasn’t been clinically validated.

Caffeine timing deserves a whole feature

The other surprise in building AfterShift was how much research exists on caffeine timing for shift workers, and how little of it reaches consumer apps.

The short version: caffeine has a half-life of about five hours. A coffee three hours before bed leaves enough in your system to disrupt sleep onset and sleep architecture. A coffee at the start of a night shift keeps you alert when you least want it, at 9am when you finally try to sleep. The right strategy depends on which way your shift is rotating, and most shift workers work it out through years of trial and error.

AfterShift builds part of that in. It sends a caffeine cut-off reminder timed to your next shift, and the cut-off adapts to what you drank and to your caffeine sensitivity. It’s not glamorous, but it answers a question shift workers otherwise answer by guesswork. The rest of the routine for the day after a night shift, from blackout shades to the nap before the next one, is in how to sleep after a night shift.

What it takes off the user’s plate

I also underestimated how much administrative load shift workers carry around their own sleep. Knowing when you slept and when your next shift starts, working out recovery in your head, deciding whether you need a nap: all of it runs in the background of their day, on top of the job itself.

AfterShift takes some of that over. Set your rotation once and the app fills the next 8 weeks of your roster, or import shifts from the calendar your employer publishes (one calendar by hand in the free version; automatic sync across several calendars with Premium). Sleep windows are planned from your shift times, actual sleep is read from Apple Health, and the wind-down, caffeine cut-off, and nap reminders are set relative to your next shift instead of the clock on the wall. The user doesn’t have to keep doing the math.

Who it isn’t for

AfterShift isn’t a general sleep tracker. If you have a stable 9-to-5 schedule, Observa is the better fit from the studio: it interprets all your Apple Health data, with sleep as one of the categories. AfterShift is for people whose schedule is the problem.

It is also not a clinical tool. Sleep disorders such as narcolepsy and sleep apnoea need a sleep clinic. AfterShift’s scores are informational and not a diagnosis. I’d rather lose users to a real doctor than oversell what consumer software can do.

Why we built it

A whole category of work keeps modern infrastructure running (healthcare, transport, public safety, manufacturing), and consumer software has mostly designed around the people who do it. AfterShift was an experiment in designing for them, starting from the assumption that their schedule is the normal life of millions of people and not a deviation from it.

If you work nights, rotations, or anything else that breaks the 9-to-5 mould, the app is on the App Store for iPhone. And if you know a nurse, paramedic, or firefighter who has been putting up with a generic sleep tracker, send them the link.