Discrepancy between subjective and objective sleep disturbances in early- and moderate-stage Alzheimer disease

Sleep disturbances such as nocturnal awakenings frequently occur in demented elderly persons and can contribute to depression, cognitive impairment, and caregiver burden. Recognizing sleep disturbances at an early stage of the disease progress is a first prerequisite of intervention and monitoring of progress. This study aimed to investigate the reliability of subjective sleep reports in early- and moderate-stage Alzheimer dementia (AD), by investigating whether they differ from matched healthy normal comparison groups with respect to the discrepancy of subjective and objective sleep estimates.

Subjective sleep was assessed using the Pittsburgh Sleep Quality Index, the Sleep Disorders Questionnaire, and the Athens Insomnia Scale. Objective sleep was estimated using actigraphy.

As compared with the normal comparison group (N = 26), AD patients (N = 55) complained less of insomnia, while their objective sleep estimates indicated, in fact, more disturbed sleep, including a longer sleep onset latency and a lower sleep efficiency. Regression analyses aimed at predicting actigraphic sleep parameter estimates from their subjective counterparts showed significant predictive value of only very few subjective sleep parameters. Subjective reports of both patients and the normal comparison group had significant value in predicting actigraphic indices of total sleep time and bedtime. In addition, subjective reports of the normal comparison group, but not of patients, were of value to predict actigraphic indices of sleep onset latency, average sleep bout duration, and sleep efficiency.

The results show that the value of sleep questionnaires is limited in early- and moderate-stage AD. Actigraphy may be essential to ensure that sleep problems do not go undetected and untreated.