The Sleep Disorders Inventory: an instrument for studies of sleep disturbance in persons with Alzheimer's disease.

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.