Let's Un-complicate: Sleep

We lie down, we close our eyes, and we wake up refreshed, right? Well… not always.

You've heard of jet lag, but have you heard of social jet lag? OK, we'll get there.

The other day, someone told me, "Sleep quantity doesn’t matter—only quality does." And while they weren’t completely wrong, they weren’t exactly right either. The truth is, cutting down sleep time doesn’t affect all stages equally, and if you’re losing sleep, the part that suffers most is the one your brain needs the most. Let's dive deep.

But let’s take a step back. Sleep isn’t just about the number of hours you spend with your eyes closed. If things like REM and NREM confuse you, simply think of sleep having two major parts: one where your body sleeps (NREM) and one where your brain cleans itself (REM). And these are controlled by two key hormones: melatonin (sleep hormone) and cortisol (wake-up hormone). Sometimes we wake up feeling like we fought a battle in our dreams, and other times we feel like we barely slept at all. That’s because sleep isn’t just “on” or “off”—it’s a whole process with different stages, a built-in body clock, and a bunch of tiny chemical messengers making sure everything works the way it should. Let’s break it down in the simplest way possible.

Sleep: Two Major Parts, Many Moving Pieces

Sleep can be broadly divided into two major functions:

Body Repair Mode (Deep Sleep / NREM Sleep) – This is when your body slows down, muscles relax, and tissues repair themselves. Your immune system gets a boost, and growth hormone is released to fix and rebuild cells.
Brain Clean-Up Mode (REM Sleep) – This is when your brain clears out toxins, organizes memories, and processes emotions. This phase is crucial for learning, mental health, and long-term brain function.

Your body cycles through these stages multiple times a night, and if you cut your sleep short, guess which one gets sacrificed? The brain clean-up phase – REM sleep. Think of sleep as a movie with different acts. Each night, your brain cycles through these acts multiple times.

1. Falling Asleep (Sleep Latency)

This is the time between lying in bed and actually falling asleep. It should take 5-20 minutes for a well-rested person. If you’re out cold in under 2 minutes? You’re probably sleep-deprived. If it takes you an hour? Your sleep system might be out of sync.

2. Light Sleep (NREM Stage 1 & 2)

Think of this as the "middle ground" between being awake and deep sleep. Your body starts relaxing, heart rate slows down, and your brain begins to tune out the world. Light sleep is crucial because it acts as a transition between wakefulness and deep sleep. If you wake up feeling groggy, chances are you spent too much time in light sleep and not enough in deeper stages.

3. Deep Sleep (NREM Sleep)

This is like the “housekeeping” stage where your body repairs itself.

Your brain slows down.
Your muscles relax.
Your body releases growth hormone to repair tissues.
The immune system gets a boost.

4. Dream Sleep (REM Sleep)

This is where dreams happen!

Your brain becomes super active (almost as if you’re awake!).
This is when you process emotions and memories.
Your body is paralysed (so you don’t act out your dreams!).
If you don’t get enough REM sleep, you might feel moody, forgetful, and foggy the next day.

The Sleep Cycle: On Repeat

Your brain cycles through these sleep stages multiple times each night. A full cycle takes about 90 minutes, and you go through 4-6 cycles per night if you’re getting enough rest. Deep sleep happens more in the first half of the night, while REM sleep happens more in the second half.

But here’s something most people don’t realize: cutting down sleep doesn’t affect all stages equally. The body prioritizes deep sleep, especially in the first half of the night. That means if you’re sleeping only 5-6 hours instead of a full 7-8, the stage that gets sacrificed the most? REM sleep. And that’s a big problem because REM sleep is where we process emotions, reinforce memory, and support brain function.

Long-term REM sleep deprivation has been linked to an increased risk of neurodegenerative diseases like Alzheimer’s and Parkinson’s, making it essential not just for rest but for long-term brain health.

The Circadian Rhythm: Your Built-in Sleep Clock

Your body runs on a 24-hour internal clock—this is called the circadian rhythm. It controls when you feel awake and when you feel sleepy.

Two major hormones run this system:

Melatonin – The “sleep hormone.” It rises in the evening when it’s dark and tells your body it’s time to sleep.
Cortisol – The “wake-up hormone.” It rises in the morning to get you alert and ready for the day.

Your circadian rhythm is heavily influenced by light. If you expose yourself to bright lights (like phones or TV screens) before bed, your brain thinks it’s still daytime and doesn’t release enough melatonin—which makes falling asleep harder.

What Can Go Wrong?

Sleep isn’t always smooth sailing. Here are some common problems:

Trouble Falling Asleep (Tossing and turning)
- Too much screen time before bed.
- Caffeine too late in the day.
- Stress and overthinking.
Waking Up Too Often (Light, broken sleep)
- Drinking too much liquid before bed.
- Disruptions like noise or temperature changes.
- Poor sleep environment (wrong mattress, bright lights, etc.).
Not Feeling Rested (Even After Sleeping 7-8 Hours)
- Not enough deep sleep (due to stress, alcohol, or an inconsistent schedule).
- Sleep apnea (a condition where breathing stops multiple times during sleep).
- Not completing full sleep cycles (due to waking up too early).

How does your behaviour affect sleep?

You've probably heard of these already. I mean these are all over the place. Let's quickly understand why and how they affect sleep

No screens before sleep: Remember the sleep hormone melatonin? Well, this guy doesn't come out if he thinks it is still daylight and you have a long way to go. So if you are super stimulated till you hit the bed, melatonin is not at it's optimal levels, so your sleep quality takes a beating. While the whole world goes after blue light (yes, it plays a role), but the mental stimulation from doom scrolling is a bigger culprit.
Don't eat too close to sleeping: Now, remember, that deep sleep happens early in your sleep cycle and when that happens, you want all your organs rested. But if your stomach has to do all the work digesting your vada pav and biriyani and that dessert, then your liver needs to step up, your entire gut needs to step up and work while your rest of the body tries to rest. And invariably they will disturb every thing else as well.
Stress - well, this one is easy. Stress just ups your cortisol, so anything that is very stimulating will keep your cortisol up. And in the process the balance between cortisol and melatonin will be off and your sleep is disrupted. So keep the arguments with your spouse well before your sleep, try to avoid exercises very close to sleep and definitely keep horror movies well before hitting the bed. Remember it is not just the stress your boss gives you, any form of stress affects your sleep.
Coffee or any stimulants. While this doesn't directly affect the hormones, coffee goes and sticks to the places where the enzyme (adenosine if you must know) attaches and asks your brain to sleep. So your brain doesn't get the signal to switch off. Some folks can kick coffee out of their system quickly (some can drink coffee and sleep like a baby), while for others coffee kicks them. Also for some people aging slows down the coffee getting kicked out of the system, so if you could drink coffee and sleep a few years back, but now it keeps you up, well, you're just getting old! (There are other ways to solve this, but that in a different blog)
Social Jet Lag - Basically this is the when your body's internal clock is not in sync with your social life. It could be that you are an early riser, but you social life keeps you up late night. Or it could be you staying way longer on weekends (beyond 2 hours of your usual bed time) and that confuses your internal clock. So keeping a consistent (within reason ofcourse) helps with sleep in the long run
Temperature: It is not just light, but also temperature that helps melatonin come out in optimal quantities. If your sleeping room is about 3 degrees lower, that is ideal for a good night's sleep.

The Takeaway: Sleep in Full, Not in Pieces

Sleep is not just “one thing”—it’s a series of stages and cycles that depend on a well-tuned circadian rhythm. If something feels off, it’s usually because something is disrupting this system.

The good news? Sleep isn’t complicated once you understand it. Respect your sleep cycle, avoid disrupting your circadian rhythm, and aim for complete sleep phases. Cutting back on sleep isn’t a shortcut—it’s a trade-off, and your brain will always pay the price, if not now, sometime in future. Respect your circadian rhythm, aim for complete sleep cycles, and don’t cut corners on REM sleep. Your future, well-rested self will thank you.

So, if you’ve ever wondered why you feel groggy despite “getting enough sleep,” now you know: it’s all about the quality AND the quantity.