Sick and Tired: Understanding and Managing Sleep Difficulties in ...

However, conducting a blood test is invasive and could in itself affect a person‟s sleep
quality when taken at night. This approach is therefore difficult to implement in clinical
research (Mayer, Leonhard, Krieg, & Meier-Ewert, 1998).
Another objective measure that can be used to detect movement, as an indicator of sleep
quality, is actigraphy. Actigraphy monitors levels of physical activity during the night
using a non-invasive device (actigraph) worn on the non-dominant arm. Natural
movements of the arm are detected by a sensor and each movement is stored as an
activity count, which can be summed over epoch intervals of one minute or more.
Although actigraphs are fitted to the arm, they have been shown to adequately assess
whole body movements (Kop et al., 2005). Actigraphs can be worn during the day and
night, and offer the advantage of being able to be used in the person‟s natural
environment for long periods, thus enabling the measurement of the variability of sleep
quality over time. Formulas are applied to the collected data to calculate the total
amount of time spent asleep, time taken to fall asleep (sleep onset latency), sleep
efficiency and the number of night-time awakenings. Actigraphs have been used
effectively to monitor both nocturnal and day-time activity levels for patients with FMS
(Kop et al., 2005; Korszun et al., 2002) and have been found to correlate well with self-
reported sleep quality and polysomnography (Hauri & Wisbey, 1992; Landis et al.,
2003). The disadvantage of actigraphy is that it relies on movement as an indication of
being awake. If a person is awake but remains motionless e.g. watching TV or resting,
actigraphy is unable to distinguish this lack of activity from being asleep and is
therefore likely to overestimate the time recorded as asleep (Hauri & Wisbey, 1992;
Menefee et al., 2000). This may be particularly problematic in people with chronic pain
conditions who are more likely to be sedentary (Kop et al., 2005).
Based on the strengths and weaknesses of objective measures of sleep quality, it is now
widely recommended that a combination of objective and subjective measures are used
in the measurement of sleep quality (Morin & Espie, 2003)
Subjective Measures
A wide range of subjective measures are currently available to assess nocturnal sleep
quality and daytime sleepiness. Each measure has its own strengths and weaknesses and
some of the most widely used measures are considered below.
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