The Sleep Disorders Inventory: an instrument for studies of sleep disturbance in persons with Alzheimer’s disease ROCHELLE E. TRACTENBERG,1 CLIFFORD M. SINGER,2 JEFFREY L. CUMMINGS,3 and LEON J. THAL4 Author information Copyright and License information Disclaimer The publisher's final edited version of this article is available free at J Sleep Res See other articles in PMC that cite the published article. Go to: SUMMARY The Sleep Disorders Inventory (SDI) is an expanded version of one item of the Neuropsychiatric Inventory (NPI). It describes the frequency, severity, and caregiver burden of sleep-disturbed behaviors during a period prior to its administration. We carried out post hoc analyses on baseline responses to the SDI in 104 persons with Alzheimer’s disease (AD) and live-in caregivers who had been recruited for a trial of melatonin in the treatment of sleep disturbance. These patient-participants averaged <7 h of sleep per night, measured by actigraph (sleep disturbance), for the 2–3-week period prior to administration of SDI. Data were from the 2 weeks prior to the baseline visit (SDI, NPI) including actigraph-derived sleep variables and 2 weeks’ worth of sleep quality ratings (SQR) kept in a diary by caregivers, plus Mini-Mental State Examination and activities of daily living assessment at baseline. The prevalence of sleep disorder symptoms ranged from 34% (waking up at night thinking it is daytime) and 82% (getting up during the night). Worse SDI scores were associated with worse cognitive, functional, and behavioral status, but not with sex, age, education or duration of dementia. SDI scores were significantly worse in individuals meeting independently established criteria for a diagnosis of ‘sleep disturbance’ (<6 h total sleep time per night) whereas demographic variables and scores reflecting cognition and function were not significantly different across this grouping. The SDI covers a wide range of sleep behaviors and provides information independent of sleep time and SQR.
Keywords: alzheimer’s disease, measurement, sleep disturbance Go to: INTRODUCTION Sleep disturbances may contribute to the behavioral, functional, and cognitive status of persons with Alzheimer’s disease (AD), as well as to the burden and health status of the caregiver (Pollak and Perlick, 1991; Pollak and Stokes, 1997). The Alzheimer’s Disease Cooperative Study (ADCS) (Thal, 1997), an NIA-sponsored consortium of AD research centers, recently completed a large clinical study of melatonin in the treatment of sleep disturbances in persons with AD (Singer et al., in press). In the present report, we describe a new instrument that assesses symptoms of sleep disturbance/disorder, the Sleep Disorders Inventory (SDI). We evaluated the responses to the SDI during the 2-week pretreatment phase of the melatonin study and describe the SDI as a novel instrument for use in assessing and quantifying sleep disturbance/disorder in AD patients.
The SDI was developed for the ADCS melatonin study and is derived from a well-known instrument, the Neuropsychiatric Inventory (NPI) (Cummings et al., 1994; Mega et al., 1996). The NPI is scored through a semi-structured interview by a clinician or researcher with a caregiver of the person with dementia. Night-time behaviors represent one area assessed by the NPI. The NPI can be administered and scored as a 10-item (excluding sleep and vegetative symptoms) or a 12-item instrument (including both). The SDI was created by expanding item 11 of the 12-item NPI and limiting the ‘observation’ period from 4 weeks to 2 weeks. According to the basic structure of the NPI, the respondent is asked a ‘screening’ question, a general indication of whether or not symptoms in that particular behavioral area are present. If the screening question is positive, then specific subquestions are asked. The NPI score is based on single frequency and severity ratings for the general behavioral area within the previous 4 weeks, rather than on quantitative ratings for each of the subquestions for that period.
The SDI consists of the seven subquestions from the NPI sleep disturbance item. Each of the subquestions was made into a separate question with frequency, severity, and caregiver distress rated by the caregiver with respect to the patient-participant for the 2 weeks prior to the visit. Thus, in contrast to a single rating for frequency and severity for all sleep disturbance-related behaviors, which would be incorporated into an overall NPI score, the SDI score is derived after the caregiver rates the frequency and severity of each of the seven separate sleep disturbance symptoms (see Table 3). Caregiver distress ratings are not part of the SDI total score, but distress is measured (see Table 3 and Appendix).
