Circadian rhythm
The circadian rhythm is the body's internal clock, regulating not just sleep and wake timing but also fluctuations in alertness, body temperature and hormone release across the day. It is influenced by light exposure, routine and, to some extent, genetics, and it varies meaningfully between individuals.
This matters for work because a person's circadian rhythm affects when they are naturally best placed to do demanding cognitive work and when they are not. Scheduling complex decisions against someone's natural low point, repeatedly and without realising it, can quietly erode the quality of their output over time.
Wearables can estimate aspects of circadian timing from sleep and temperature patterns, and Sloane can use this, where available, as context for the timing of its suggestions, such as noting that a demanding meeting has landed at a point in someone's day when they are not usually at their sharpest.
Circadian patterns shift with travel, shift work and irregular schedules, which is another reason Sloane tracks a rolling personal baseline rather than a fixed assumption about anyone's day.
Related terms
- Sleep debt, The cumulative shortfall between the sleep a person has actually had and the amount their body appears to need, built up over several nights rather than one.
- Readiness, A daily estimate of how prepared a person is to take on demanding work, based on overnight physiological recovery relative to their own baseline.
- Personal baseline, The rolling normal range for a specific individual across their signals, used as the point of comparison for deciding whether something has genuinely changed.