In news that will come as no surprise to anyone over the age of 30, new research has found it gets harder to sleep as we get older.

But it’s not young children, partners or weather sabotaging our precious rest, but biology, according to American sleep researchers.

A review of scientific literature published in the medical journal Neuron found adults begin to lose their ability to lapse into deep, restorative sleep from about their mid-30s.

And it’s no coincidence, the researchers say, that this is also about the time we start to show signs of aging.

More frighteningly, however, report co-author Professor Matthew Walker said, is that lack of sleep has also been linked with a host of deadly diseases, particularly those affecting the brain.

“Sleep changes with aging, but it doesn’t just change with aging; it can also start to explain aging itself,” he said.

“Every one of the major diseases that are killing us in first-world nations — from diabetes to obesity to Alzheimer’s disease to cancer — all of those things now have strong causal links to a lack of sleep.”

“And all of those diseases significantly increase in likelihood the older that we get, and especially in dementia.”

Researchers have found that, as the brain ages, neurons and circuits in the areas that regulate sleep slowly degrade, resulting in a decreased amount of non-REM sleep.

Sleep deprivation is defined as insufficient sleep for 14 or more days in the past 30 days | Data from 2008-2009 BRFSS

Non-REM sleep is characterized as a deep state of sleep, without rapid eye movement, dreaming, and bodily movement.

Non-REM sleep plays a key role in maintaining memory and cognition, which explains the connection between brain conditions such as dementia and Alzheimer’s disease.

Walker, who leads the Sleep and Neuroimaging Laboratory at the University of California at Berkeley, said there remains some debate as to whether older adults need less sleep, or they cannot generate the sleep that they need.

“The evidence seems to favor one side — older adults do not have a reduced sleep need, but instead, an impaired ability to generate sleep,” he said.

“The elderly therefore suffer from an unmet sleep need.”

The authors stress that there is variability between individuals when it comes to sleep loss.

However, the review did find that women seem to experience far less deterioration in non-REM deep sleep than men.

With loss of deep sleep starting in the mid-thirties, Walker said it must be seen as an important health issue.

“We need to recognize the causal contribution of sleep disruption in the physical and mental deterioration that underlies aging and dementia,” he said.

“More attention needs to be paid to the diagnosis and treatment of sleep disturbance if we are going to extend healthspan, and not just lifespan.”