Table 2: Standardized sleep questionnaires.



Epworth Sleepiness Scale (ESS)13

The ESS is a scale intended to measure daytime sleepiness by use of a very short questionnaire. The questionnaire asks the subject to rate his or her probability of falling asleep on a scale of increasing probability from 0 to 3 for eight different situations [13]. The scores for the eight questions are added together to obtain a single number. A number in the 0-9 range is considered to be normal while a number in the 10-24 range indicates that expert medical advice should be sought [13].

Insomnia Severity Index 14-16

The ISI is a seven-item self-report questionnaire. The seven answers are added up to get a total score. The scale assesses sleep-onset and sleep maintenance difficulties, associated distress, and interference with daily functioning. Each item is rated on a 0-4 scale.

The time period is the past fortnight. The guidelines for the interpretation of scores are: no clinically significant insomnia (0-7), subthreshold insomnia (8-14), clinical insomnia of moderate severity (15-21) and severe clinical insomnia (22-28) [16].

Pittsburgh Sleep Quality Index (PSQI) [17,24]

The Pittsburgh Sleep Quality Index (PSQI) is a self-rated questionnaire which assesses sleep quality and disturbances over a 1-month time interval. Nineteen individual items generate seven "component" scores: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication, and daytime dysfunction. The sum of scores for these seven components yields one global score. A global PSQI score greater than 5 is supposed to distinguish good and poor sleepers [17].

Restless Legs Syndrome- Diagnostic Index (RLS-DI)19

The RLS-DI consists of 10 items which are related to the essential diagnostic criteria established by the International RLS Study Group (five items) as well as their supportive criteria (3 items) and features associated with RLS (2 items). Items have to be completed using three categories per item that address frequency of occurrence of symptoms or certainty of presence or absence of other diagnostic information. Within the present study only five items were explored.