The effects of aging on sleep parameters in a healthy, melatonin-competent mouse model

Background: Sleep disturbances are common maladies associated with human age. Sleep duration is decreased, sleep fragmentation is increased, and the timing of sleep onset and sleep offset is earlier. These disturbances have been associated with several neurodegenerative diseases. Mouse models for human sleep disturbances can be powerful due to the accessibility to neuroscientific and genetic approaches, but these are hampered by the fact that most mouse models employed in sleep research have spontaneous mutations in the biosynthetic pathway(s) regulating the rhythmic production of the pineal hormone melatonin, which has been implicated in human sleep. Purpose and method: The present study employed a non-invasive piezoelectric measure of sleep wake cycles in young, middle-aged and old CBA mice, a strain capable of melatonin biosynthesis, to investigate naturally-occurring changes in sleep and circadian parameters as the result of aging. Results: The results indicate that young mice sleep less than do middle-aged or aged mice, especially during the night, while the timing of activity onset and acrophase is delayed in aged mice compared to younger mice. Conclusion: These data point to an effect of aging on the quality and timing of sleep in these mice but also that there are fundamental differences between control of sleep in humans and in laboratory mice.