Sleep and Fatigue — Page 220, Lesson 358

I want to walk you through the symptoms of fatigue and how to delay its onset, then we’ll look at the state of vigilance and hypovigilance. Let’s start with the symptoms of fatigue. Fatigue isn’t just feeling tired — it produces a specific set of measurable effects on your performance. The symptoms listed here include a lack of awareness, diminished motor skills, and obvious tiredness. You’ll also see diminished vision, increased reaction time, and short-term memory problems. There’s something called channelled concentration — that means you focus on one thing to the exclusion of everything else, which is dangerous in the cockpit. You become easily distracted, your instrument flying deteriorates, and you make more mistakes overall. Irritability and abnormal mood swings are common, along with a reduced scan — meaning you stop looking around the cockpit and outside effectively. You may revert to ‘old’ habits, meaning you fall back on earlier, less efficient ways of doing things, and your communication decreases. Every one of these is a red flag for a pilot. Now, how do you delay the onset of fatigue? The book gives a list of proactive actions. First, accept that fatigue is a potential problem — denial won’t help. Plan your sleep strategies proactively; that means you schedule sleep ahead of the next day’s activities, not just hope you’ll get rest. Use exercise as part of your relaxation period and ensure you are physically fit. Avoid alcohol — it disrupts sleep quality. Eat a regular and balanced diet. Have your emotional and psychological life under control — stress outside the cockpit feeds fatigue inside it. Ensure cockpit comfort, make sure food and drink are available for long flights, and ensure your seat is properly adjusted. These are all within your control. Let’s move to vigilance and hypovigilance. The scientific definition of vigilance is different from what we normally mean by the term. The state of vigilance is the degree of activation of the central nervous system. That activation can vary from deep sleep all the way up to extreme alertness, and it is controlled by your circadian cycle — your internal body clock. A vigilant person is an alert person. So in normal circumstances, as workload increases, so does vigilance. Your central nervous system ramps up to meet the demand. There’s an important note here: vigilance is a very different mechanism from attention. Attention is covered separately in Chapter 7 of the book, but for now, understand that vigilance is about your overall level of nervous system activation, not where you point your focus. You can be highly vigilant but have poor attention, or vice versa. That figure shows how jet lag differs when travelling westwards versus eastwards — we’ll get to that in context shortly, but for now, keep in mind that the circadian cycle controlling vigilance is the same cycle that gets disrupted by jet lag.