Dados do Trabalho

Título

Development of new instrument for the assessment of insomnia symptoms: the Inventory of Symptoms and Consequences of Insomnia

Introdução

Symptom scales are a reasonable alternative to assess the severity of insomnia, both as a complementary tool for diagnosis and to follow patients under treatment. The available scales for insomnia symptoms severity are usually based on a single domain. Knowing that clinical manifestation of insomnia is heterogeneous, an instrument that assesses multiple domains could provide a more detailed evaluation.

Objetivo

To develop a new tool to assess insomnia symptoms.

Métodos

The Inventory of Symptoms and Consequences of Insomnia (ISCI) was developed to cover different domains of symptoms and consequences, based on a series of statements answered according to their frequency in the last 2 weeks (5-point scale, “never” to “everyday”). The list of items was idealized to cover the following domains: Primary insomnia complaints, cognitive symptoms, physiological symptoms, daytime functioning, dysfunctional beliefs, stress, sleep self-perception, and sleep hygiene. It was tested in a 2-step process. First, the inventory was submitted for evaluation by 4 board-certified sleep psychologists, who rated them for clarity, relevance, and appropriateness on a 1-5 scale. Following, the inventory was sent for a database of 2.000 respondents of both sexes from 20 to 80 years old. Respondents also completed the Insomnia Severity Index (ISI), which was used to assign insomnia severity levels. Receiver operating characteristic (ROC) curves were built using dichotomous results at the ISI as reference (thresholds for mild, moderate and severe insomnia) and the scores at the ISCI.

Resultados

The inventory was initially composed of 56 items. Upon the judges’ analyses, the average scores for all items were 4.41±0.34 for clarity, 4.9±0.2 for relevance and 4.9±0.3 for appropriateness, and 1 item was deleted due to a low average score. Based on a following factorial analysis, the inventory was reduced to 48 questions. The final sample of respondents was composed of 1603 participants (mild insomnia: 32%, moderate: 24%, severe: 5%). For mild symptoms threshold, the ROC analyses demonstrated an area under the curve (AUC) of 0.87 (p<0.001) with sensitivity of 85.4, specificity of 76.0 and a suggested diagnostic threshold of >54. For moderate threshold, the AUC was 0.97 (p<0.001) with sensitivity of 90.9, specificity of 92.0 and diagnostic threshold at >86. For severe threshold, the AUC was 0.99, with sensitivity of 97.0, specificity of 95.5 and diagnostic threshold at >100.

Conclusões

The ISCI has good diagnostic properties when compared with the ISI, especially in discriminating individuals with severe insomnia symptoms.

Palavras -chave

Sleep Initiation and Maintenance Disorders; Psychometrics; Insomnia severity