This is a great question. In general, sleep inertia is worse the sleepier you are. This is because high levels of sleepiness can decrease the time it takes you to get into deep sleep and can make sleep deeper. But this is not always the case with all types of fatigue. Remember there are a number of types of fatigue, e.g., mental, physical, lethargic and sleep-related fatigue, etc.

Sleep inertia severity is not at all related to workload, like 14 days of flying because this does not guarantee an increase in sleep-related fatigue, but it can be related to poor sleep caused by childcare interruptions of sleep. Sleep inertia could be worse and last longer if you are sleepier before you take your nap or sleep. But the real question is “Should we be concerned about the severity or duration of sleep inertia if we are following recognized SOP’s for managing it?” The answer is “Aware of it but not too concerned” The SOP is to ensure that the person who has woken up from sleep is not engaged in any safety critical activities for 20 minutes after sleep. Instead of safety critical activities, the sleeper/napper should be engaged in mentally stimulating activities and physical activities for the 20 minutes. This 20 minutes will allow the sleep inertia to dissipate.

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