How much sleep you get and the quality of your sleep may be associated with mental deterioration and Alzheimer's Disease.
Four new studies offered evidence that poor sleep habits may do more than make you cranky.
In one study too little or too much sleep was equated with two years' brain aging.
That large study involved data on more than 15,000 U.S. Women .
It suggested that women who slept five hours a day or less, or nine hours a day or more, had lower average mental functioning than participants who slept seven hours per day.
A separate study concluded that people with sleep apnea, disrupted breathing during sleep, were more than twice as likely to develop mild thinking problems or dementia, compared to problem-free sleepers.
Another study suggests that excessive daytime sleepiness may predict diminished memory and thinking skills, known as cognitive decline, in older people.
The studies on sleep and brain function were presented at this week's Alzheimer's Association annual meeting in Vancouver.