Stress Effects, Fatigue and Management

The previous lesson built the machinery: the curve, the model, the fight or flight response, the stressors. This one follows the machinery into its consequences. What stress does over minutes (acute), over months (chronic, through Selye's three stages), what it does to thinking and behaviour, and what its cousin fatigue does alongside it — ending with the part the syllabus grades most practically: how stress and fatigue are actually managed, from the next five minutes to a change of lifestyle.

Anxiety: stress without a stressor

The previous lesson filed anxiety under imaginary stress; here is the full account. Anxiety is stress experienced with no stressor present: the sense that a future risk exists, joined to a felt inability to cope or a lack of self-confidence. The relationship between stress and anxiety is therefore anticipation: anxiety is the stress of a perceived future demand rather than a present one, and it runs on the same machinery, strongly enough that anxious apprehension alone can trigger the full physiological stress response. Its effects on performance follow directly: anxiety inevitably degrades performance, and a resurfaced anxiety (an old unpleasantness recalled by a scene, a noise, a smell) can distort perception itself, so the anxious pilot is not merely uncomfortable but reading the world less accurately. (The trait that makes one person more anxious than another belongs to the personality dimensions; here the subject is the state itself.)

Acute stress, arousal and vigilance

The general effect of acute stress is whole-body mobilisation: the short-term effects of a sudden stressor are caused by the fight or flight response of the previous lesson, sympathetic branch first, resources up, senses sharpened. The chain the syllabus wants connected runs: stressors raise arousal, and arousal sets vigilance, which in its scientific sense is the degree of activation of the central nervous system, running from deep sleep to extreme alertness under the control of the circadian cycle (and a different mechanism from attention). In normal circumstances rising workload raises vigilance, and with little or no stress vigilance drops; but the whole chain obeys the inverted U, so stress helps vigilance only on the near side of the break point.

Chronic stress and the general adaptation syndrome

The general adaptation syndrome (GAS) is the mechanism by which the individual reacts to an outside threat, real, perceived or anticipated, and the biological reaction to continued stress runs through Selye's three stages: alarm reaction, resistance, exhaustion. The alarm reaction is the previous lesson's fight or flight: sympathetic mobilisation under adrenaline. Resistance is the parasympathetic prolongation, powered by a different stress hormone, cortisol, which converts fats to sugar to maintain the energy supply (and acts on the brain to improve the memory of stress situations, which is why such events are remembered so intensely). Exhaustion arrives when exposure lasts too long and the energy resources are depleted: it usually affects specific parts of the body, is temporary if rest comes, and if allowed to continue without respite can result in death as the defence mechanism shuts down. The hormones leave waste to be eliminated (a source of secondary effects), and if the stressor is coped with or removed, the body gradually returns to homeostasis.

The syndrome's reaction is also sliced a second way, into three kinds: the psychological reaction (the brain registers fear, alarm or crisis), the psychosomatic reaction (the brain triggers the release of hormones, adrenaline and sugars into the blood), and the somatic reaction (the responses of the body's organs to those hormonal and chemical releases). Chronic stress, meanwhile, collects its toll in health: the effects show earliest in the gastrointestinal system (nausea, indigestion, diarrhoea and, in time, ulcers), with evidence linking stress to coronary heart disease and high blood pressure, raised risks of asthma, headaches, sleep disorders and neuroses, and more allergies, skin diseases, colds and influenza.

What overload looks like

The syllabus wants the symptoms of human overload in both registers. The physiological ones: sweating, dry mouth, difficulty in breathing, increased heart rate and fatigue. The psychological ones: anxiety, apprehension and fear. Behind them come the behavioural effects of stress: restlessness, trembling, a nervous laugh, longer taken over tasks, excessive changes in appetite, more smoking and drinking, and mood swings with two characteristic shapes — some pilots turn aggressive toward the crew or ATC, others submit with resentment and frustration, and either way the result is a loss of flexibility. A third pattern rushes into decisions on fewer parameters, and the error rate rises with the hurry.

The cognitive effects cut deepest. Forgetfulness is an early symptom; thinking and concentration shrink; priorities and decisions stop coming. Correct actions are forgotten and procedures learnt in the past are substituted, which is called regression (the old type's flows resurfacing under pressure). Fixation, the mental block, makes it impossible to review what has been done and consider other solutions, and confirmation bias becomes compulsive: a repeated search for information that agrees. Above all, stress makes the mind limit its attention to the factors it feels it can cope with and ignore inputs that may be vital, the not-seeing-the-wood-for-the-trees loss of situation awareness behind many accidents. Passengers debriefed after escaping a burning aircraft reported how quiet it had seemed: the screams around them were never registered, and it is commonly accepted that auditory information is the first to be discarded under extreme stress.

Cumulative, transferred, and reduced by success

Three facts about stress bookkeeping, all introduced last lesson and graded from this one. Stress is cumulative: add a stressor to an existing irritation and the level rises disproportionately, even if the original situation has been resolved. It transfers between situations: the pilot who argued on the ground carries the argument's stress into an unrelated problem in the air, and trouble at work rides home just as easily. And it is reduced by success: completing a stressful task successfully lowers the stress experienced when a similar situation arises later, because the stress model's feedback has cut the perceived demand and grown the perceived ability. Experience, in the model's terms, is banked stress relief.

Underload and overload at work

On the flight deck the two ends of the curve degrade effectiveness in mirrored ways. Overload narrows attention, rejects vital information and multiplies errors, as above. Underload has its own source list, and the syllabus wants it: monotony, reduced workload, simple or repetitive tasks, constant monotonous noise, low lighting, high temperature, isolation, sleep debt and fatigue (and, honourably, the period just after a meal). Its symptoms are the danger signs of hypovigilance: drowsiness with the head dropping forward and a vague, persistent discomfort that keeps you shifting in the seat, slower sensory perception (staring at an instrument longer than normal before its information registers), preoccupation with a problem entirely outside the current situation, and moodiness with a reluctance to talk. Hypovigilance itself is sleep showing on an EEG during waking activity, akin to a microsleep, and it cannot be totally eliminated in flight (there is even a theory it helps control energy consumption), only forestalled.

Fatigue: the two types

Fatigue is deep tiredness, and like stress it is cumulative. Its general causes: lack of restful sleep, lack of physical or mental fitness, excessive physical or mental stress and anxiety, and desynchronisation of the body cycles (jet lag). What makes it dangerous is its insidiousness: tiredness is instantly recognisable and socially admissible, but a fatigued pilot can be unaware of the condition until a crisis forces the realisation, and even an aware pilot hesitates to admit it, as though it confessed being not up to the job. The professional duty runs both ways: recognize the symptoms in yourself, and just as importantly in the other members of your crew.

The syllabus splits fatigue in two. Short-term fatigue is akin to tiredness: caused by lack of sleep, hard physical or mental exertion, crew scheduling, a long duty period, lack of food or jet lag, easily recognized, and remedied by not flying and sufficient rest. Long-term (chronic) fatigue is much harder to recognize and admit: its causes include lack of physical or mental fitness, a stressful marriage coupled with problems at work, financial worries and a high workload; it is subjective (one pilot tolerates more than the next before it sets in); and the rule is unconditional: anyone who suspects chronic fatigue must take themselves off flying.

Fatigue symptoms, and delaying the onset

The symptom list is long because fatigue reaches everything: lack of awareness, diminished motor skills, obvious tiredness, diminished vision, increased reaction time, short-term memory problems, channelled concentration, easy distraction, poor instrument flying, increased mistakes, irritability and abnormal mood swings, a reduced scan, reversion to old habits, and a decrease in communication. The strategies that prevent or delay the onset: accept that fatigue is a potential problem, plan sleep strategies proactively, use exercise as part of relaxation and stay fit, avoid alcohol, eat a regular and balanced diet, keep your emotional and psychological life under control, ensure cockpit comfort, ensure food and drink are available for long flights, and ensure the seat is properly adjusted.

Forestalling hypovigilance in flight adds its own actions: fly with sufficient sleep credit, know the danger signs listed above, move position regularly and if possible get up and walk a few steps, maintain social contact with the rest of the crew, and keep mentally and physically active, since vigilance decreases with lack of stimuli. Crew members should also take their meals at different times: staggered meals stagger any hypovigilance among the crew, and the same habit serves the food-safety rule against poisoning more than one pilot at once. There is no absolute amount of sleep that must be achieved: sleep as much as you need.

Coping with stress

Coping begins with awareness: recognizing that you are suffering from stress is fundamental, and most of the road to identifying the sources. After that, coping strategies fall into three categories. Action coping reduces the demand itself: remove the problem or change the situation (refuse the marginal-weather flight, though the refusal may substitute a new stressor such as loss of employment; delay the take-off until the forecast improves, which cuts the demand without substituting anything; hand tasks to other crew members or to ATC), or remove yourself entirely (a change of job, a divorce), remembering that removal often just swaps stressors. Cognitive coping reduces the impact instead: the brain's unconscious defence mechanisms (repression, denial) can hide a stressor from awareness altogether, and conscious rationalization or detachment shrinks the perceived magnitude ('pretend it's the simulator detail you flew last week'). Symptom-directed coping treats only the symptoms, with drugs in the broad sense (coffee, tea, alcohol, tobacco), and the stressor remains until addressed separately. The circle closes on the behavioural effects above: the evidence that stressed people smoke more, overeat and drink more has led to the theory that these apparently self-abusive behaviours may themselves be attempts at exactly this form of stress management.

On the flight deck, coping is built in advance: a thoroughly professional approach to training widens the range of automatic responses and shrinks the set of unknown situations (hence simulator emergencies practised in safety), learning from the past includes other people's past, and thorough preflight briefing and preparation buy anticipation. CRM shares and allocates tasks so no individual overloads, uses every member's knowledge, and improves shared awareness; a good atmosphere helps, and humour can be an effective antidote to stress. When stress threatens safety anyway, the five guidelines: keep it simple and basic (fly the aircraft); accept the situation rather than concealing facts or danger; use all crew resources; the captain, unless incapacitated, makes the decisions and controls the situation; and never give up, because there is always a suitable response.

Short-term and long-term stress management

The syllabus distinction: short-term methods are the action-coping moves made in or around the moment (remove the stressor, change the demand, hand over tasks, apply the five guidelines), while long-term stress management means a change of lifestyle or counselling, and a good programme is both preventative (keeping stress levels to a minimum) and curative (reducing the levels that already exist). The long-term techniques: health and fitness programmes (regular exercise reduces tension and anxiety, makes fatigue easier to withstand, and improves cognitive function and reaction times), relaxation techniques (meditation, self-hypnosis, yoga, biofeedback), religious practice (a genuine help to many, with one caution: a fatalistic belief can stop a person trying to resolve their own problems), and counselling, professional or simply talking to friends and colleagues, whose principle is the stress model itself: change how the situation is perceived (cognitive coping) and, where needed, prompt the behavioural change (action coping). Pilots, trained to project authority, are often reluctant to admit stress; the admission is not weakness but the first, necessary step. To grow tolerance the summary names three weapons: experience, learning and CRM.

The fatigue risk management system

Fatigue also gets managed at the organizational scale. The ICAO definition the syllabus quotes: a fatigue risk management system (FRMS) is a data-driven means of continuously monitoring and managing fatigue-related safety risks, based upon scientific principles, knowledge and operational experience, that aims to ensure relevant personnel are performing at adequate levels of alertness. The key words earn their places: data-driven (rosters and fatigue reports measured, not guessed at), continuous (monitoring, not a one-off study), scientific principles and operational experience together, and a stated aim of adequate alertness rather than mere legal compliance.