Body movements during night sleep and their relationship with sleep stages are further modified in very old subjects

The night sleep of 12 healthy subjects aged 76-98 was polygraphically investigated in order to analyse body movements and their association with sleep stages at very old age; this group was compared with 11 healthy old subjects aged 61-75 years. In very old subjects sleep is less punctuated by body movements and the association of body movements with each sleep stage is further modified compared to less old subjects. Short-lasting movements emerge indifferently from stage 1, stage 2 and REM sleep, but are significantly less frequent in SWS. Furthermore, in very old subjects the probability of awakening after body movements is higher than in old subjects, suggesting that sleep is more vulnerable to the occurrence of body movements than at previous ages. The difficulty in the elderly to maintain a stable state expresses the inability to sustain and coordinate stable physiological activities characteristic of the old age. In addition, the presence of numerous awakenings, not preceded by movements, supports the hypothesis that the awakening in the very old people may be a sudden event, as should be confirmed by the study of other behavioural and physiological activities preceding awakening.