PERSPECTIVES

So why do most of us feel so poorly when we reduce our sleep time? Natural selection has imposed a certain amount of sleep on us to restrict activity to appropriate times of day and to reduce long-term nonvital energy expenditure. The pressure to sleep operates by reducing brain activity. Although individ-uals with naturally short sleep times are not at elevated risk compared to those with natu-rally long sleep times, repeated sleep depri-vation below the body’s programmed level is stressful and likely to impair health. Certain hormonal processes are linked to sleep. How-ever, these are not universal, but rather are species and age specifi c ( 8, 12)