Doctor explains how sleep debt silently harms mind and body

Sleep deprivation can take a serious toll on the body, even if a person feels they are functioning normally, according to Sabine Kapasi, CEO at Enira Consulting Pvt Ltd and Founder of ROPAN Healthcare.

Many people show up to work after sleeping for only a few hours, and aside from occasional grogginess, loud yawns and a manageable headache that coffee seems to fix, they may feel like they are still functioning fine. However, what happens inside the body can tell a very different story, even when short-term effects feel manageable.

This worsens when poor sleep becomes a habit. Late nights, repeated scrolling on the phone and disrupted recovery can slowly build up sleep debt, which silently wreaks havoc.

To understand the impact of sleep deprivation on health, HT Lifestyle spoke to Kapasi, who is also a UN advisor. She helped explain what happens inside the body when poor sleep becomes a regular habit.

Do you know if you're sleep deprived?

Kapasi recalled the findings of a 14-day study in which subjects slept for only four hours, instead of the recommended eight to nine hours. The results showed a decline in reaction time, attention and mental processing within days.

This was alarming because many participants still believed they were functioning normally, even as their performance continued to drop on paper. This is what makes sleep deprivation so unsettling: there is a gap between perception and biological reality. A person may think everything is fine when, in reality, their brain and body may be silently struggling under the weight of sleep debt.

How poor sleep affects cognitive performance

Kapasi said: "The cognitive decline caused by sleep debt shows itself as slower decision-making, delayed reactions, reduced concentration, attenuated memory and a diminished ability to control emotion."

This means poor sleep extends beyond physical exhaustion. It affects how a person thinks, responds, remembers and handles emotions.

In turn, this can impact real-world environments such as offices, hospitals, roads, trading floors and factories. Kapasi observed that small delays add up to operational errors, impaired judgment and lower productivity.

How poor sleep affects the body

On the physiological front, poor sleep affects the body in several ways, highlighting how important sleep is as a cornerstone of good health for both mind and body. Kapasi said several changes can happen simultaneously inside the body.

She explained: "Cortisol levels rise, keeping the nervous system in a prolonged state of tension, while testosterone and hormonal activity related to recovery decrease. The result is inconsistent energy, slower physical recovery, mental fatigue and reduced resilience under pressure."

Sleep debt builds up over time

What makes sleep deprivation worse is that it is cumulative in nature. Kapasi explained that it builds up over time, not after just one poor night of sleep, but rather many nights of poor sleep quality.

On why the gap between perception and biological reality exists, Kapasi said: "People often adapt psychologically to the fatigue, which creates the illusion that they are coping. Biologically, performance continues declining underneath that perception."

In simple terms, when poor sleep becomes a habit, a person may start to believe that a little tiredness is normal and get used to it. But becoming habituated does not mean the body stays unharmed. The brain, hormones and overall well-being all get adversely impacted.

Recovery takes longer than expected

Kapasi gave a reality check on recovery, saying it is much slower than people make it out to be. Sleeping till noon on weekends will not reverse the effects of poor sleep. This is why Kapasi stressed the importance of acting now and ensuring proper sleep every night.

Note to readers: This article is for informational purposes only and not a substitute for professional medical advice. Always seek the advice of your doctor with any questions about a medical condition.