Sleep is one of a few important lifestyle activities that allows us to develop a healthy life. We spend almost a third of our lives sleeping.

“When you’re tired, the emotion regulator of your brain becomes more reactive; while the logical, calm part of your brain that usually keeps emotions in check becomes less active. You will feel that you are more reactive over matters, even trivial ones. You find yourself becoming more easily irritated and frustrated”

Most of us know that sleep is important, but many people tend to neglect or dismiss it when asked to make a choice. Between work deadlines, family commitments, and late-night scrolling, sleep often becomes the first thing we choose to reduce. Make that choice often enough, and we will quickly experience the effects of lack of sleep.

What Happens When the Brain Doesn’t Rest

As we go on with our daily activities, we use up resources and build up waste in our brain. It would be helpful to think of sleep as your brain’s nightly “service appointment.” It’s when your brain clears out waste, resets its wiring, and prepares for the next day.

Without enough sleep, the brain slows down. Thinking becomes harder, reactions become slower, and everything feels a little blurry or “off.” This is why people often describe sleep deprivation as feeling foggy — it’s literally your brain running without proper maintenance.

How Sleep Loss Affects Thinking and Emotions

One of the earliest signs of poor sleep is difficulty concentrating. You may catch yourself rereading the same line, zoning out during conversations, or struggling to stay organised.

Memory also takes a hit. When you sleep, your brain moves important information into long-term storage. Without that rest, those memories don’t “stick,” so you forget things more easily.

The brain also uses sleep to help make sense of the memories. Without adequate sleep, the processing of these memories gets interrupted and that can result in a feeling of frustration or distress in some circumstances.

Decision-making is affected too. Whether it’s choosing what to eat or handling a work issue, a tired brain will have limited resources to use, and it slips into “survival mode”, and becoming more impulsive, less thoughtful, and more likely to overlook important details.

Similarly, ever notice how everything feels harder after a bad night’s sleep?

That’s because sleep directly affects the emotional centres of the brain. When you’re tired, the emotion regulator of your brain becomes more reactive; while the logical, calm part of your brain that usually keeps emotions in check becomes less active. You will feel that you are more reactive over matters, even trivial ones. You find yourself becoming more easily irritated and frustrated.

A lack of sleep also increases stress hormones like cortisol and adrenaline, and this can result in making your body more tense, restless, and easily overwhelmed. These stress hormones also suppress your immune system, making you more susceptible to infections.

A continuous lack of sleep can increase the risk of developing a mental health condition. This can either be due to actual physical changes to the brain, such as bipolar disorder and depression; or due to an accumulation of the impact of lack of sleep, such as burnouts and anxiety.

Vice versa, these mental health conditions can impact physical health and result in worsening co-morbid conditions, such as diabetes mellitus and hypertension, or developing new physical conditions.

Simple Habits for Better Sleep

The good news is that sleep isn’t something that requires complex changes to maintain. Good quality sleep starts with behaviour that promotes good sleep hygiene. Some of these include a regular sleeping time, no caffeine after late midday, a regular pre-bed winding down routine, avoiding electronics in bed, not doing intensive exercises in the evening and many more.

When you prioritise sleep as an important lifestyle habit, you also take care of your mind and physical health. A well-rested brain thinks clearer, feels better, and handles life with more resilience. You will in turn, get more out of life.

This article is authored by Dr. Eugene Koh Boon Yau, Consultant Psychiatrist (Visiting), Columbia Asia Hospital Seremban.