Still tired after a full night’s sleep? A new study claims to know the reason why you’re always exhausted

A woman with dark hair lies in bed yawning because she is so tired and ready to sleep

(Image credit: Getty Images)

Good news if you live in industrial society (and if you're reading this, you probably do); we're sleeping longer and sleeping better. So why has the Center for Disease Control declared bad sleep a public health epidemic?

New research suggests that it isn't a lack of sleep that's making us all so tired — it's a mismatch in our circadian rhythms.

Comparing the sleep habits of people in industrial and non-industrial societies, the analysis found that even though non-industrial societies sleep less, improved circadian function means they don't spend all day tired.

Key takeaways of the research

Industrial societies sleep longer than non-industrial societies
Despite increased sleep time, people still report fatigue
Researchers theorize this is due to circadian disruption

Let's start with the good news. Research from February 2025 comparing sleep in industrial and non-industrial societies has learnt that in the industrial world, we're sleeping longer and enjoying better sleep efficiency (that's the time in bed spent actually asleep.)

A woman with afro hair wearing blue shirt waking up in three quarter bed with grey sheets, stretching our arms — (Image credit: Getty Images)

Now the bad news: we're still really, really tired. The CDC found roughly 13.5% of adults are exhausted most days and sleep deprivation can affect both our mental and physical wellbeing.

What gives? Researchers propose that if it's not lack of sleep causing fatigue, the answer might lie in our circadian rhythms.

While those in non-industrial societies sleep less, they display a better circadian function. In the industrialized world — where we're surrounding by artificial lights and air conditioning — our circadian function is diminished. Our body clock isn't aligned with our behavior.

Termed the "circadian mismatch hypothesis", researchers suggest that those in non-industrialized societies are able to remain active and alert on less sleep because they're following their circadian rhythms.

And in the industrial world, poor circadian function means even after a solid eight hours, we're still exhausted.

4 ways to support your circadian rhythm

If you feel tired after a full night's sleep, you might need to get your circadian rhythms back on track. Here are some steps to take...

1. Get plenty of sunlight, especially in the morning

Light exposure is essential to regulating circadian rhythms. Sunlight in the morning indicates it's time to get up, while dark evenings remind you to go to bed.

Woman waking up and stretching in bed bathed in sunlight — (Image credit: Getty Images)

One major difference between industrialized and non-industrialized society is the prevalence of artificial lighting. Those of us who work in an office will know how inescapable overhead lighting can be and these bright lights can be confusing for your circadian rhythms.

To counteract this, try to get outside as much as possible during the day, allowing your body clock to experience natural light. As another plus, fresh air can help fight fatigue.

2. Turn off the lights (and the heating)

People in industrial societies typically have access to light and warmth on demand. This cozy setting can benefit your rest (there's a reason why we're sleeping longer) but on the flip side, technological interventions can play havoc with your circadian rhythms.

In non-industrial society, warmth and light exposure is largely dependent on the weather, keeping your body clock in tune with external rhythms.

While we're not suggesting you sit in the dark and cold (we've had fire far longer than LED lights), consider adjusting your internal setting to better match the outdoors. Low lighting in the evening and a cooler bedroom temperature have both been linked to better sleep.

3. Try segmented sleep

There's evidence to suggest our ancestors enjoyed a segmented or biphasic sleep pattern. Essentially, sleeping in two shifts with a notable wake up period in the middle.

A man sleeping on his side in bed with white sheets and white night clothes — (Image credit: Getty Images)

Waking up in the night is normal — few of us actually sleep through. However, the modern approach is to simply roll over, close your eyes, and keep your fingers crossed you drop off quickly.

But it might be better to follow in our forebear's footsteps and treat these late night wake-ups as an opportunity to socialize. Or, if your partner doesn't appreciate being nudged awake at three in the morning, a chance to reflect, ruminate and relax.

4. Listen to your body

Changing your habits to suit a non-industrialized society while living in an industrialized world isn't an easy task. However, one of the best ways to offset your circadian mismatch is to actually listen to your body.

When do you naturally start to feel sleepy? And when do you wake up without your alarm clock? Understanding your sleep chronotype can help you create a sleep schedule that's kind to your circadian rhythms, while still in keeping with the requirements of day to day life.

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Ruth is a staff writer at Tom’s Guide, covering all things mattress and sleep. She has a deep interest in the link between sleep and health, and has tried enough mattresses to know the right bed really can make a difference to your wellbeing. At Tom’s Guide she writes to help people sleep better, from how-tos to the latest deals to mattress reviews, and has interviewed an array of specialists who share her passion. Before joining the team at Tom’s Guide, Ruth worked as a sleep and mattress writer for our sister website, TechRadar.