For as long as I can remember, the standard advice has been clear: get eight hours of sleep. It’s in every wellness article ever written. One of those health rules that feels as settled as “drink more water” and “eat your vegetables.”

But a growing body of research is complicating that picture. And the findings are worth paying attention to — especially if you’ve been stressing about not hitting that magic number.

The Study That’s Getting Attention

A large-scale study published in late 2025 by researchers at the University of Sydney tracked over 45,000 adults across five countries. They measured not just sleep duration, but sleep architecture — time spent in each stage of sleep, including deep sleep and REM.

The headline finding: sleep quality and structure were stronger predictors of daytime functioning, mood, and cognitive performance than total duration alone.

Someone who sleeps six and a half hours of high-quality sleep may function better than someone who gets eight hours of fragmented, shallow sleep. Duration matters, but we’ve been over-indexing on one metric while ignoring others.

What “Sleep Quality” Actually Means

When researchers talk about sleep quality, they’re looking at several factors:

Sleep efficiency. This is the percentage of time in bed that you actually spend asleep. If you’re lying in bed for nine hours but only sleeping for six, your sleep efficiency is low. High sleep efficiency — generally above 85 percent — is associated with better outcomes.

Sleep continuity. How often do you wake up during the night? Frequent or prolonged awakenings fragment your sleep and reduce its restorative benefits. This is one reason why alcohol before bed is problematic — it increases sleep fragmentation even if total sleep time doesn’t change much.

Deep sleep duration. Deep sleep is when the most physical restoration happens. Growth hormone is released, tissue repair occurs, and the brain clears metabolic waste. Lifestyle factors like exercise, stress, and caffeine timing all play a role in how much deep sleep you get.

REM sleep. This is the stage most associated with emotional processing and memory consolidation. Disrupted REM sleep is linked to mood disturbance and impaired learning.

Why This Matters

The cultural fixation on eight hours has had some unintended consequences.

For one, it creates anxiety. There’s even a term for it: orthosomnia — the obsessive pursuit of perfect sleep, often driven by wearable trackers. People who fixate on hitting exactly eight hours can end up more stressed about sleep, which ironically makes sleep worse.

It also leads people to spend too much time in bed. If you’re lying in bed for nine or 10 hours trying to force sleep, you’re training your brain to associate bed with wakefulness. Sleep clinicians call this “sleep extension,” and it’s one of the first things addressed in CBT-I.

And it ignores individual variation. Some people genuinely function well on seven hours. Some need closer to nine. The “right” amount varies between individuals and changes across your lifespan.

What You Can Do

If this research has you rethinking your approach to sleep, here are some practical takeaways:

Stop fixating on the number. Instead of counting hours, pay attention to how you feel during the day. Are you alert? Can you concentrate? Those are better indicators of whether your sleep is working for you than a number on a tracker.

Focus on consistency. Going to bed and waking up at roughly the same time each day — including weekends — is one of the most reliable ways to improve sleep quality. Your circadian rhythm thrives on predictability.

Watch your caffeine window. Caffeine has a half-life of about five to six hours. If you’re having coffee at 3pm, there’s still a meaningful amount of caffeine in your system at 9pm. For most people, cutting caffeine after midday makes a noticeable difference to sleep depth.

Get morning light. Exposure to bright light in the first hour after waking helps anchor your circadian rhythm and improves both sleep onset and sleep quality at night. In an Australian summer, even a few minutes outside in the morning is enough.

Be cautious with sleep trackers. Consumer wearables can give you a rough sense of your sleep patterns, but they’re not clinically accurate. Use them as a general guide, not a diagnostic tool. And if tracking your sleep is making you more anxious, take the tracker off.

Consider CBT-I if you’re struggling. If you have chronic insomnia, cognitive behavioural therapy for insomnia is the gold-standard treatment — more effective than medication in the long term. Your GP can refer you, and online programs like This Way Up offer evidence-based CBT-I.

The Bigger Picture

I think this research is a healthy correction. We needed to move past the oversimplified “eight hours or else” messaging and start talking about sleep in a more nuanced way.

Sleep is important — deeply important. But the goal isn’t to hit a specific number every single night. The goal is to build habits that support good-quality rest, and to pay attention to what your body is actually telling you.

Some nights you’ll sleep seven hours and feel great. Some nights you’ll sleep eight and feel terrible. That’s normal. What matters is the overall pattern, not any single night.

Rest well. But don’t lose sleep over it.