What Your Sleep Habits Say About Your Intelligence

Sleep can be a useful indicator of a person’s overall health. The quality of our shut-eye might say a lot about our dementia risk and even heart health.

Some research suggests it might reflect our intelligence, too.

Spikes in our brain activity as we nap, called “spindles”, and our “chronotype” – or our natural sleep-wake cycle – have been linked to different cognitive abilities in studies.

Here’s what the science says:

According to a 2026 meta-analysis published in the journal Frontiers in Sleep, faster “sleep spindles” were linked to greater cognitive abilities.

Sleep spindles are very brief (we’re talking 0.5-second to 3-second) bursts in brain activity that happen during the non-rapid eye movement (NREM) stage of sleep. NREM sleep usually accounts for 70-80% of our total sleep time.

They get their name from how they look on a brain scan – the waves “spike” as these “burstlike signals” arise.

Researchers think they might help with memory consolidation. And in the 2026 Frontiers paper, scientists linked the strength of people’s higher-frequency “sleep spindles” to higher intelligence.

How long these bursts last didn’t seem to matter when it came to intelligence.

We also get lower-frequency sleep spindles, which are slower and appear closer to the front of the brain.

The more densely-packed the frequency of these are during sleep, the likelier we are to score better during cognitive tests. This seems to be truer fo adults than children, and held even more true still for older adults.

Using data from more than 26,000 people involved in the UK Biobank, scientists found “night owls” tended to do 7.5%-13.5% better on cognitive tests than “early birds”.

Intermediate sleepers, or those who were a mix of both waking types, also did 10.6%-6.3% better than those who only rose early.

The study’s lead author, Dr Raha West, said: “Our study found that adults who are naturally more active in the evening (what we called ‘eveningness’) tended to perform better on cognitive tests than those who are ‘morning people’. Rather than just being personal preferences, these chronotypes could impact our cognitive function.”

However, experts stressed that this doesn’t mean every night owl is smarter than every early bird. Their results reflected an overall trend, not an absolute rule.

And regardless of sleep type, getting too much or too little sleep – less than seven or more than nine hours a night – was linked to lower cognitive scores.