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