Being able to sleep well in old age can cut the risk of developing a wide range of mental and physical disorders such as Alzheimer’s disease, say scientists.

As we grow old, our nights are frequently plagued by bouts of wakefulness, bathroom trips and other nuisances as we lose our ability to generate the deep, restorative slumber we enjoyed in youth, researchers said.

They reviewed studies which show that the ageing 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.

Though older people are less likely than younger adults to notice and/or report mental fogginess and other symptoms of sleep deprivation, poor sleep leaves them cognitively worse off, researchers said.

The shift from deep, consolidated sleep in youth to fitful, dissatisfying sleep can start as early as the 30s, paving the way for sleep-related cognitive and physical ailments in middle age.

“The parts of the brain deteriorating earliest are the same regions that give us deep sleep,” said Bryce Mander from the University of California (UC) Berkeley in the US.

Ageing 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,” researchers said.

“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 of UC Berkeley.

“Nearly every disease killing us in later life has a causal link to lack of sleep. We have 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,” said Matthew Walker, professor at UC Berkeley.

Age-related changes in brain activity in sleep

Unlike more cosmetic markers of ageing, such as wrinkles and grey hair, sleep deterioration has been linked to conditions such as Alzheimer’s disease, heart disease, obesity, diabetes and stroke, researchers said.

The study was published in the journal Neuron.