Researchers at the University of California, Berkeley, have found that the unmet sleep needs of the elderly elevate their risk of memory loss and a wide range of mental and physical disorders.
In an article published Wednesday in the journal Neuron, the researchers argue that unlike more cosmetic markers of aging, such as wrinkles and gray hair, sleep deterioration has been linked to such conditions as Alzheimer's disease, heart disease, obesity, diabetes and stroke.
“Nearly every disease killing us in later life has a causal link to lack of sleep,” said the article's senior author, Matthew Walker, a UC Berkeley professor of psychology and neuroscience. “We've done a good job of extending life span, but a poor job of extending our health span. We now see sleep, and improving sleep, as a new pathway for helping remedy that.”
Though older people are less likely than younger cohorts to notice and/or report mental fogginess and other symptoms of sleep deprivation, numerous brain studies reveal how poor sleep leaves them cognitively worse off.
Moreover, the shift from deep, consolidated sleep in youth to fitful, dissatisfying sleep can start as early as one's 30s, paving the way for sleep-related cognitive and physical ailments in middle age.
Walker and fellow researchers cite studies that show the aging brain has trouble generating the kind of slow brain waves that promote deep curative sleep, as well as the neurochemicals that help us switch stably from sleep to wakefulness.
“The parts of the brain deteriorating earliest are the same regions that give us deep sleep,” said article lead author Bryce Mander, a postdoctoral researcher in Walker's Sleep and Neuroimaging Laboratory at UC Berkeley.
Aging typically brings on a decline in deep non-rapid eye movement (NREM) or “slow wave sleep,” and the characteristic brain waves associated with it, including both slow waves and faster bursts of brain waves known as “sleep spindles.”
Youthful, healthy slow waves and spindles help transfer memories and information from the hippocampus, which provides the brain's short-term storage, to the prefrontal cortex, which consolidates the information, acting as the brain's long-term storage.
“Sadly, both these types of sleep brain waves diminish markedly as we grow old, and we are now discovering that this sleep decline is related to memory decline in later life,” said Joseph Winer, a doctoral student in Walker's lab.
Another deficiency in later life is the inability to regulate neurochemicals that stabilize our sleep and help us transition from sleep to waking states. These neurochemicals include galanin, which promotes sleep, and orexin, which promotes wakefulness.
“The American College of Physicians has acknowledged that sleeping pills should not be the first-line kneejerk response to sleep problems,” Walker said. “Sleeping pills sedate the brain, rather than help it sleep naturally. We must find better treatments for restoring healthy sleep in older adults, and that is now one of our dedicated research missions.”
Also important is the question of quantity versus quality. “Previously, the conversation has focused on how many hours you need to sleep,” Mander said. “However, you can sleep for a sufficient number of hours, but not obtain the right quality of sleep.”
“Indeed, we need both quantity and quality,” Walker was quoted as saying in a news release.