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conditions, and to which we would add cultural expectations of sleep). They


conclude that a major limiting factor in objectively measuring sleep quality, as


opposed to quantity, involves the lack of a standard definition. Without this, a


single global objective measure of sleep quality will be impossible to develop. For


anthropological studies, where notions of sleep loss and sleep quality from both


emic and etic perspectives are particularly pertinent, the development and imple-


mentation of validated methods for objectively measuring the nature of sleep


experience seem both impractical and implausible. The development of individually


relevant and culturally adaptable subjective methods for assessing sleep quality


appears to hold much greater promise.


Measuring Tiredness and Fatigue


Tiredness and fatigue, although used interchangeably in daily life, are considered


two separate phenomena: tiredness (carrying the same meaning as sleepiness) is


defined as the need to sleep or the propensity to doze or fall asleep (Curcio et al.


2001 ), whereas fatigue is defined as lacking energy or feeling exhausted (Shahid


et al. 2010 ). Tiredness/sleepiness and fatigue may co-occur, but are objectively


measured using different techniques.
Acute fatigue is technically defined as a psychological or physiological state of


reduced mental or physical performance capability resulting from sleep loss or


extended wakefulness, circadian phase, or workload (mental and/or physical


activity) that can impair alertness and ability to safely perform normal duties. It is


often measured in the workplace, characteristically in employment that involves


shift-work or changing time zones (among airline pilots, nurses, and air traffic


controllers). Where identification of acute fatigue is needed, it is generally assessed


using a variety of objective computer- or handheld device-based tests requiring


alertness and concentration. The Psychomotor Vigilance Test (PMVT), for


instance, is a sustained attention task that measures the speed with which subjects


respond to a visual stimulus (Lim and Dinges 2008 ). The test runs for 5–10 min


using a device that records reaction time and the number of missed responses. It is


simple to administer, requires little training, has been clinically validated, and is


sensitive to changes in fatigue levels. Such assessments are important where mental


fatigue may cause reductions in concentration or impaired judgment with disastrous


consequences for others.


Chronic fatigue is a characteristic of several psychological and physical disor-


ders such as depression, chronic fatigue syndrome, cancer, and HIV. In a clinical


setting, there is no objective test available for the assessment of chronic and


pathological fatigue, leaving clinicians reliant on a wide range of subjective rating


scales such as the Fatigue Severity Scale (FSS) or the Fatigue Questionnaire


(FQ) (Shen et al. 2006 ). Some of these scales focus upon the impacts and behav-


ioral manifestations of fatigue and may be relevant to the experiences of parents
suffering with Baby-Lag.


3 Baby-Lag: Methods for Assessing Parental Tiredness and Fatigue 33

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