Waking up feeling exhausted after a night of vivid dreams is a common experience, but University of the Sunshine Coast sleep researchers say the dreams themselves are probably not to blame.
Instead, the tiredness is more likely linked to disrupted sleep and waking during key stages of the sleep cycle.
Researchers from USC’s Thompson Institute say many people mistakenly believe they have been dreaming all night when they wake feeling groggy and unrefreshed.
“We all dream, and most of us dream multiple times a night, whether we remember it or not,” said Dr Danielle Wilson, a sleep scientist and research fellow at the Thompson Institute.
Most dreaming occurs during rapid eye movement (REM) sleep, which accounts for about 20 to 25 per cent of total sleep time. People typically experience four to six REM cycles each night, with the longest occurring closer to morning.
According to the researchers, people are much more likely to remember dreams if they wake during or immediately after REM sleep.
“Someone who was sure they dreamed all night probably had a completely normal night of REM sleep.
They just happened to wake during the emotionally charged parts, and those are the ones that stuck,” Dr Wilson said.
During REM sleep, the brain is highly active while the body’s muscles are essentially paralysed, preventing people from acting out their dreams. Areas of the brain linked to emotion become highly active, creating vivid experiences that can feel incredibly real.
Despite this activity, dreaming itself does not appear to cause fatigue.
“The tiredness is not a consequence of dreaming. It’s a consequence of when you woke up and what stage you were pulled from,” Dr Wilson said. Researchers say waking from REM sleep can trigger sleep inertia, the thick, foggy feeling that makes it difficult to become fully alert. Even brief awakenings throughout the night can also reduce time spent in deep sleep, which is critical for physical restoration and recovery.
The researchers note that regularly remembering vivid dreams, feeling as though dream activity has increased, or waking tired most mornings may indicate fragmented sleep rather than excessive dreaming.
“When sleep is cut short or is repeatedly broken, the brain makes up for lost REM time on subsequent nights, spending a higher proportion of sleep in that stage,” Dr Wilson said.
“If you regularly remember most of your dreams, feel like the number of dreams you have has increased, or find yourself waking up tired most mornings, your fragmented sleep may mean the brain isn’t getting the deep, restorative stages it needs.”
The findings were published in an article for The Conversation by USC sleep health experts Dr Wilson and Professor Yaqoot Fatima, together with research program manager Dr Nisreen Aouira from Let’s Yarn About Sleep.