The organization of rapid eye movement activity during rapid eye movement sleep is further impaired in very old human subjects.

Rapid eye movement activity (REMA) during rapid eye movement (REM) sleep was studied in seven very old (`old-old') subjects. Beyond global quantitative features (REMA density), we evaluated the organizational aspects of REMA, that is its occurrence in burst mode, which were compared to a group of younger elderly subjects (`young-old'). REMA density in `old-old' subjects is not signi®cantly different from that of `young-old' subjects. The same lack of difference in the two groups is found for the number of REMA bursts. By contrast, the duration of REMA bursts is reduced in the `old-old' subjects, as well as the `burst state-to-burst-state' probability, i.e. the probability for successive inter-REMA time intervals to be part of the same REMA burst. Our results clearly show that the trend towards an impairment of REMA organizational aspects continues with aging. This is consistent with the hypothesis that sleep disorganization keeps worsening with age. However, it is of interest to observe that the capability of producing REMA bursts is preserved despite aging. q 2001 Elsevier Science Ireland Ltd. All rights reserved.