Sleep disorders in people with dementia.

Sleep disorders often precede cognitive impairment by many years. This is partly because some degenerative diseases originate in the hypothalamus and brain stem, which means fragmented sleep, daytime napping and sleep-phase disorders are early signs of these diseases. However, recent research indicates that amyloid proteins are removed from the brain during deep sleep so poor sleep can increase the amyloid plaques seen in Alzheimer's disease. It is also known that sleep-disordered breathing can lead to hypoxia, increasing vascular dementia.