Age-related changes during a paradigm of chronic sleep restriction.

Fragmented and restricted sleep is a common problem for the human elderly. There is evidence that aging impairs sleep in animals as well. After sleep deprivation, older animals have less sleep rebound. Despite increasing complaints of reduced time for sleep in contemporary society, few studies have examined chronic sleep restriction protocols in animals. Therefore, the aim of the present study was to evaluate the effects of chronic sleep restriction on the sleep patterns of aged rats. Using the single platform method, 22-month-old male rats were submitted to 18 h of sleep restriction followed by 6 h of total sleep opportunity. The sleep-wake cycles of these rats were recorded for 6h/day throughout the 12-day procedure. The results showed that total sleep time and NREM sleep were reduced during the 12-day sleep restriction period. However, rebound REM sleep was only significant on day 6. A negative rebound was also seen, particularly during the last days of the chronic sleep restriction period. Furthermore, sleep latency and mean wake bout length progressively increased during the protocol. These findings indicate that older rats have an inability to restore their sleep patterns during extended sleep deprivation.