Vienne Julie, Spann Ryanne, Guo Fang, Rosbash Michael
Department of Biology, Brandeis University, Waltham, MA.
Howard Hughes Medical Institute, National Center for Behavioral Genomics, Brandeis University, Waltham, MA.
Sleep. 2016 Aug 1;39(8):1613-24. doi: 10.5665/sleep.6032.
Physiological studies show that aging affects both sleep quality and quantity in humans, and sleep complaints increase with age. Along with knowledge about the negative effects of poor sleep on health, understanding the enigmatic relationship between sleep and aging is important. Because human sleep is similar to Drosophila (fruit fly) sleep in many ways, we addressed the effects of aging on sleep in this model organism.
Baseline sleep was recorded in five different Drosophila genotypes raised at either 21°C or 25°C. The amount of sleep recovered was then investigated after a nighttime of sleep deprivation (12 h) and after chronic sleep deprivation (3 h every night for multiple nights). Finally, the effects of aging on arousal, namely, sensitivity to neuronal and mechanical stimuli, were studied.
We show that fly sleep is affected by age in a manner similar to that of humans and other mammals. Not only do older flies of several genotypes have more fragmented sleep and reduced total sleep time compared to young flies, but older flies also fail to recover as much sleep after sleep deprivation. This suggests either lower sleep homeostasis and/or a failure to properly recover sleep. Older flies also show a decreased arousal threshold, i.e., an increased response to neuronal and mechanical wake-promoting stimuli. The reduced threshold may either reflect or cause the reduced recovery sleep of older flies compared to young flies after sleep deprivation.
Further studies are certainly needed, but we suggest that the lower homeostatic sleep drive of older flies causes their decreased arousal threshold.
生理学研究表明，衰老会影响人类的睡眠质量和时长，且睡眠问题会随着年龄增长而增加。鉴于睡眠不足对健康的负面影响已为人所知，了解睡眠与衰老之间神秘的关系十分重要。由于人类睡眠在许多方面与果蝇睡眠相似，我们在这种模式生物中研究了衰老对睡眠的影响。
记录了在21°C或25°C下饲养的五种不同果蝇基因型的基线睡眠情况。然后在夜间睡眠剥夺（12小时）和慢性睡眠剥夺（连续多晚每晚剥夺3小时）后，研究睡眠恢复量。最后，研究了衰老对觉醒的影响，即对神经元和机械刺激的敏感性。
我们发现果蝇睡眠受年龄影响的方式与人类和其他哺乳动物相似。与年轻果蝇相比，几种基因型的老年果蝇不仅睡眠更碎片化，总睡眠时间减少，而且在睡眠剥夺后也无法恢复同样多的睡眠。这表明要么睡眠稳态较低，要么无法正常恢复睡眠。老年果蝇还表现出觉醒阈值降低，即对促进觉醒的神经元和机械刺激的反应增强。与年轻果蝇相比，觉醒阈值降低可能反映或导致老年果蝇在睡眠剥夺后恢复睡眠减少。
当然还需要进一步研究，但我们认为老年果蝇较低的睡眠稳态驱动力导致了它们觉醒阈值的降低。
