Individual Differences in Sleep/Wake Regulation and Performance

Kurzfassung

Inter-individual variance in biomedical data can be large. This often makes it difficult to draw clear conclusions, and a large inter-individual variance has traditionally been considered an unwanted problem rather than an interesting aspect. However, variance not only arises from measuring errors but can also be due to systematic, trait-like differences among individuals, the investigation of which may reveal new insight into the function and regulation of biological processes. In the field of sleep-wake regulation and performance, variance may conceivably arise from disparities in the underlying homeostatic and circadian processes, or it may arise from trait-like differences in the tolerance of sleep loss or circadian misalignment such as occur during shiftwork and jetlag. Among the groups that have been compared with each other are young and older individuals, men and women, short sleepers and long sleepers, morning and evening persons (“larks” and “owls”), as well as groups with specific genetic polymorphisms. For example, it was reported that with regard to sustained attention, healthy older individuals (65-76 years) tolerate sleep loss better than young ones (18-30 years), that short sleepers (sleep duration <6.5 h) live under and tolerate a higher homeostatic sleep pressure than long sleepers (>9 h), and that a difference in the timing of optimal performance between morning and evening persons may be due to a disparity in the length of endogenous circadian period. Furthermore, polymorphisms in genes involved in circadian rhythmicity (Period-3; PER3) and in the metabolism of the neuromodulator adenosine (Adenosine-deaminase; ADA) have been reported to predict increased vulnerability to sleep deprivation as reflected in impairments in attention and other aspects of cognitive performance. The systematic study of inter-individual differences and their biological basis is important because 1) it is likely to provide new insights into the function and regulation of sleep, 2) it may help identify those individuals at risk for suffering the negative consequences of sleep loss and circadian misalignment, 3) it may help us develop adequate policies and countermeasures against those consequences (“personalized medicine”).