The RIS is a new self-rating scale with ten items, developed to measure symptoms of PI with special emphasis on psychological symptoms.
The scale covers the characteristic cognitive, emotional and behavioural aspects of PI. These items are essential target symptoms in CBT-I
[36, 37]. With an average time for completion and evaluation of less than three minutes, it is a highly efficient tool both for research and clinical practice. The RIS discriminates well between PI and healthy controls. We propose to consider a score from 0–12 points as normal and a higher score as indicative of PI symptoms.
The relatively high sensitivity and specificity values of our scale may be explained by the fact that patients were recruited from a tertiary referral center with many insomnia patients showing high symptom load and a severe degree of insomnia. This is illustrated by the finding that the sensitivity and specificity of the PSQI in our samples were similarly high and even higher than in the original study
. Final conclusions about the sensitivity and specificity of the RIS would therefore require additional studies in independent samples. However, it should be noted that the RIS has neither been designed nor validated as a tool for the diagnosis of PI or for differentiating between subtypes of insomnia.
Component analysis revealed that the RIS differentially assesses four factors. Besides “sleep depth” and quantitative aspects of sleep, the factor “fearfully focussing on insomnia” is especially interesting for an insomnia scale. We consider that the combination of psychological aspects that characterize psychophysiological insomnia as well as qualitative and quantitative aspects of sleep all represented in one short scale is the innovative aspect of this scale when compared to existing insomnia scales. Although this multifaceted structure of the RIS indicates its potential for differential assessment of different dimensions of insomnia (sleep quality, sleep quantity, focus on insomnia and medication intake) it should be noted that the RIS has been developed and validated as a single scale and should also be primarily used so.
The RIS was sensitive for detecting improvements after CBT-I in sleep parameters and target symptoms. Both the PSQI and RIS were comparable in measuring effects of CBT-I on sleep latency, sleep duration and hypnotic intake. In addition, the RIS detected effects in target symptoms of CBT-I, especially in thinking about sleep. This is an important result, since modification of dysfunctional beliefs is one of the central aspects of CBT-I
. Effects were also seen in sleep-related fear, indicating the sensitivity of the RIS to the emotional aspects of PI. The changes observed in the perception of sleeplessness suggest that the RIS also covers sleep misperception, which is regarded as one of the central aspects of PI
[14, 38] . Thus similar to the ISI
 and the Dysfunctional Beliefs and Attitudes about Sleep Scale
, the RIS is sensitive to psychotherapy-specific target symptoms and is therefore proposed as a complementary scale with a special focus on psychological symptoms of PI.
Beyond measuring severity of PI, RIS (and especially its different dimensions) may be a useful instrument in disentangling the psychological symptoms from the symptoms of the organic sleep disorders. In a recently published study, we showed that psychophysiological insomnia-specific symptoms contribute to a less compliant attitude towards a treatment of sleep apnea with continuous positive airway pressure
. This study was done with the RIS and showed new aspects in comparison to another study that was performed with the ISI earlier
. While Nuygen et al., could not see any impact of insomnia symptoms on CPAP compliance with the ISI, two items in the RIS (“I feel that I have not slept all night” and “I am afraid to got to bed because of my disturbed sleep”) specifically correlated with compliance
There are limiting factors in this study design. In this study the RIS has been validated using a sample of insomnia patients with a broad spectrum of severity, ranging from outpatients to patients who received inpatient CBT-I. This is reflected by the broad distribution of the scores (Figure
1). Nevertheless, a potential selection bias cannot be excluded since the sample stems from a specialized tertiary referral centre. Therefore evaluation of the RIS in other samples is strongly encouraged. For the English version normative studies are necessary. Further studies should also investigate the relation to objective sleep data and the comparability to other short insomnia scales recently published. Also the sensitivity of the RIS for other therapeutic interventions such as pharmacotherapy should be addressed. In addition it was not validated against objective measures such as actigrapy or polysomnography. However, since this scale focuses on psychological symptoms and since a wide range in objective sleep parameters in insomnia patients are known
, we consider this rather a minor problem. Another problem is that this scale was not cross validated against a current insomnia scale. We chose the PSQI because in the evaluation period of the RIS there have been a lot more studies done on insomnia patients with the PSQI rather than the ISI. Furthermore, it was not our purpose to design an alternative to ISI, but rather a new measurement for psychophysiological symptoms and sleep parameters in a short scale with good feasibility.