If you’re one of the many people who find it increasingly difficult to get a good night’s sleep as they get older, a new study shows that it appears you’re not imagining that you used to sleep better. In fact, a change in your brain is likely causing the difficulty in getting to sleep and sleeping deeply.
Researchers led by scientists at the University of Kent in the UK found that ageing causes a significant reduction in sensitivity to light in the part of the brain that controls circadian rhythms. The circadian rhythm is your body’s internal clock that cycles between wakefulness and sleepiness over a roughly 24-hour period, dictating when you fall asleep and when you wake.
It’s long been known that the changes between light and darkness impact this rhythm, because exposure to light suppresses the production of a hormone called melatonin, which helps us sleep. The researchers have now found that as we age, a glutamate receipt in our brain, which is used to transmit information on light exposure, becomes less effective in setting our circadian rhythm.
That means the rhythm can become unstable, in rough terms because your brain can no longer perceive as effectively whether you’re exposed to light.
“The breakthrough could help target treatments that aim to improve both physiological and behavioural circadian clock ‘re-setting’ in older people,” the university said of the study’s findings.
The National Sleep Foundation in the US says that it’s a common misconception that our need for sleep declines with age. In fact, we continue to need the same amount of sleep throughout adulthood, but many studies show that many older adults take longer to fall asleep, wake more often during the night and have less deep sleep than the norm.
“Research suggests that much of the sleep disturbance among the elderly can be attributed to physical and psychiatric illnesses and the medications used to treat them,” the foundation says.
The Kent University study, however, now suggests that declining quality of sleep may have a biological cause, rather than being driven by illness or medication – because our body isn’t responding to the signals for sleep in the way it did when we were younger.
Of course, there are also health and pharmaceutical reasons for sleeplessness, including sleep apnoea and restless legs. And a link has been made between difficulty sleeping and Alzheimer’s disease, because poor sleep is thought to contribute to higher amyloid lvels. These plaques are commonly found at higher concentrations in the brains of people with Alzheimer’s.