[Insomnia Severity Index: some indicators about its reliability and validity on an older adults sample]. / Insomnia Severity Index: algunos indicadores acerca de su fiabilidad y validez en una muestra de personas mayores.

ABSTRACT

INTRODUCTION: The Insomnia Severity Index (ISI) is a short instrument developed to assess insomnia severity from which there is no study in Spain that guarantees its psychometric properties. AIM: To examine the reliability, factorial structure, and convergent and discriminant validity of the Spanish version of the ISI in an older adult sample. SUBJECTS AND METHODS: A sample of 230 older adults, aging from 56 to 87 years old (71,11 +/- 5,56) filled in the ISI, together with Athens Insomnia Scale-5 (AIS-5) and Mini Mental State Examination (MMSE). RESULTS: Principal component analysis shows only one factor which explains 68.99% of total variance, with an internal consistency reliability equals 0.91. Regarding its validity, ISI shows statistically significant positive correlations with AIS-5 (r = 0.93) and negative with MMSE (r = -0.15). Moreover, it differentiates between men and women, people with and without cognitive impairment, and people with and without medical treatment. CONCLUSION: First data of the Spanish version of the ISI endorse single-dimensional structure, with an appropriate internal consistency reliability, and evidences of its measures validity.