Surgeon with 25 years of experience warns less than 6 hours of sleep can increase risk of heart disease, certain cancers

Dr Jeremy London explains that sleeping fewer than 6 hours or more than 9 hours is dangerous, and aiming for 6-8 hours of quality rest is key.

We’ve all felt the 'brain fog' that follows a restless night, but according to a heart surgeon, the stakes of sleep deprivation are far higher than just a bad mood. In a February 25 Instagram video, Dr Jeremy London, a US-based cardiothoracic surgeon, who brings over 25 years of medical experience to the table, detailed the physiological 'foundation' that sleep provides and why ignoring your internal clock could be a matter of life and death.

The U-shaped curve of health risk

Dr London shared that when it comes to rest, more isn't always better, and less is definitely dangerous. He described the relationship between sleep duration and health risks as a U-shaped curve. According to him, sleeping fewer than 6 hours or more than 9 hours was dangerous, while the sweet spot was aiming for 6 to 8 hours of quality rest.

"Well, we all know that not enough sleep isn't good for us, but it's actually a U-shaped curve. Your risk is high due to insufficient sleep. The sweet spot is around 6 to 8 hours, and then it actually goes up after about 9 hours. We all have our own internal clocks, and we're not nocturnal," Dr London explained, noting that staying within that middle window is vital for long-term health.

Hormones, hunger and circadian rhythms

A major takeaway from Dr London’s insights was the importance of our circadian rhythm. As humans, we are biologically designed to be diurnal — waking with the sun and resting when it sets. When we fight this natural rhythm, our internal chemistry begins to misfire.

He explained, "We wake up with the sun. We go to bed when the sun goes down. And when that gets off, our hormones start firing at the wrong time. Think about how your appetite changed after you pulled an all-nighter, how you craved different things, how your mood changed, and your overall stress level."

The long-term consequences

While Dr London was quick to reassure people that one stormy night won't ruin your health, he issued a stern warning regarding chronic sleep issues. Failing to prioritise a routine for years can lead to a cascade of severe medical conditions: "Let me be clear. I'm not talking about one bad night's sleep affecting your overall health. This is a chronic problem. And if you do this over time, you can have an increased risk of type 2 diabetes, increased risk of cardiovascular disease, and certain cancers. Sleep is absolutely foundational to our overall physiology."

"Sleep is absolutely foundational to our overall physiology," Dr London concluded. For a man who spends his days repairing hearts, his message was clear: the best way to keep your heart healthy might just be to stay in bed — at least for six hours.

Note to readers: This report is based on user-generated content from social media. HT.com has not independently verified the claims and does not endorse them.

This article is for informational purposes only and not a substitute for professional medical advice.