Associations between quantitative sleep EEG and subsequent cognitive decline in older women

This study examined whether quantitative sleep EEG changes pre-date the clinical development of mild cognitive impairment and/or incident dementia. Data from a nested case-control sample of women (mean age 83 yrs) from the Sleep and Cognition Study, an ancillary study to the longitudinal Study of Osteoporotic Fractures, were characterized as cognitively normal (MMSE>24) at the time of a baseline PSG is reported. A total of 85 women who developed new mild cognitive impairment or dementia by objective cognitive testing 5 years after PSG are included. Higher EEG power values were found in the dementia/mild cognitive impairment group for the alpha and theta bands in non-REM sleep and alpha and sigma bands in REM sleep. There was no group difference in traditional PSG measures of sleep architecture and sleep stage distribution, sleep apnea and periodic limb movement indices. These results suggest that quantitative EEG changes which precede the clinical onset of cognitive decline and the diagnosis of dementia in elderly women may be a potential biomarker for imminent cognitive decline.