Recording EEG in this demented, institutionalized population was extremely difficult, and only certain patients could tolerate the equipment for any length of time. In addition, the EEG records showed much diffuse slowing, which made it difficult to score sleep or wake. Vitiello et al. suggest that in Alzheimer's Disease, impaired sleep may be secondary to degenerative changes in the brainstem regions and pathways that regulate sleep as well as in the cortical tissues that generate EEG slow-wave activity during sleep (7
). It is possible that the recordings from the frontal/parietal areas exaggerated the amount of diffuse slowing. Nevertheless, it has been well documented that there is a high prevalence of EEG abnormalities among older patients with dementia, delirium, and other cognitive impairments (8
). The waking EEG of demented patients shows abundant diffuse slow activity, similar to that seen in sleep (8
). Bliwise, in his review of sleep and dementia (8
), concluded that the slowing of the EEG activity makes discriminations between sleep and wake extremely difficult. Therefore, in older, demented patients, the EEG cannot be used as a “gold standard”.
In fact, in his review of the use of activity in psychology and medicine, Tryon presented evidence that questioned whether EEG measurement is a reliable and valid gold standard (9
). He continued to review validity studies that have shown that with actigraphy, one can record microarousals not normally detected by EEG. Since the EEG was originally validated against behavioral criteria, Tryon concludes that one cannot fault actigraphy for disagreeing with EEG any more than one can fault EEG for disagreeing with behavior (9
). Disagreement between behavioral observations and EEG most often occur during the transition from wake to sleep, i.e. sleep onset. Most disagreements between actigraphy and EEG also occur on the definition of sleep onset.
For this reason, minute-by-minute rates of agreement were not presented for these data. Agreement rates ranged from 0.33 to 0.85 for maximum activity and from 0.29 to 0.95 for sum activity, indicating that there was no consistently acceptable level of agreement between the two methods when evaluation was made minute-by-minute. While estimations of total sleep time and wake time can be reliably made, given the problems with scoring EEG, it is unclear how reliable minute-by-minute data actually are.
The estimations of total-sleep time and wake time from EEG and from Actillume were significantly correlated. In order to more fully examine the problems with scoring EEG, the two experienced sleep technologists, each with over 20 years’ experience, both scored a sub-set of the EEG records. The inter-rater correlation for total sleep on these difficult records was 0.87, very similar to the correlations between EEG and Actillume. Sleep/wake activity based on the Actillume was also compared with observations of sleep/wake. The sensitivity and specificity of the Actillume was well within acceptable limits when compared to observation. The Actillume is clearly superior to observation since it will unobtrusively record 24-hour periods without staff intervention.
Given the difficulties in both recording and interpreting EEG in demented nursing-home populations, the Actillume seems to be a viable, reliable alternative for studying sleep/wake activity. If any studies of etiology or treatment are to be done, the Actillume appears to be one of the most feasible techniques for doing so in this population.