Jet lag, cancer risk and a master clock

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Did you know that jet lag is linked to cancer risk?! But don’t cancel your post-pandemic travel plans just yet. I’m talking about a different kind of jet lag. The eternal jet lag of the tired mind.

It’s October. That means uni students are buried under a pile of final assignments. For me personally it means my sleep cycle is all over the place. So, I decided to do some reading about how this might affect my health (the list is too long, just try to sleep well).

One thing led the other and I became fascinated about our circadian clock and its role in everything we do. The circadian clock is responsible for tuning our body to our environment and timing our cells functions. Turns out it does not only control our sleep cycle but also our metabolism and energy consumption. Even our cells reproduction!

There are studies that linked increased cancer risk to exposure to artificial light and a disruption of the circadian clock. But… how does this happen?

It happens in two ways. The first, it affects our endocrine system and how our hormones are secreted. Researchers have been studying the link between melatonin and breast cancer for decades. They found that exposure to light at night reduces melatonin secretion. This increases cancer risk because melatonin inhibits the reproduction of cancerous cells and tumor growth.

The second is related to cells reproduction in general. The circadian rhythm controls what stages of the cell cycle happen at each time on the day. During the day, our cells replicate DNA. In the evening, a kind of quality control system kicks in. This quality control system checks that the processes happening during the day didn’t replicate any damaged DNA. If everything is okay, the cells start dividing late at night.

However, if during quality control, there are anomalies in the DNA, two things can happen. The first, a repair system tries to fix these anomalies and then reproduction starts. If the repair system fails, the cells sacrifice themselves for the greater good. Altruistic little fellas, these cells.

What happens when we are exposed to light at night is that our circadian rhythms get disrupted, and the quality control and repair process get interrupted. This leads to reproduction of damaged DNA, which may include cancerous cells.

This means that a disrupted circadian clock (or eternal jet lag), increases cancer risk. But it’s not all bad news. The same clock can be used to enhance cancer treatment.

Studies show that the effect of therapeutic drugs can be enhanced by synchronising the treatment to the circadian clock. Biologists from Virginia Tech determined that the absorption and distribution of drugs vary according to the circadian rhythms of the cells that are targeted. This means that administering treatment at the right time would make the drug more efficient. And what’s even best, will reduce side effects for the patients.

This method was proven successful in the treatment of chronic conditions such as hypertension, arthritis, and asthma. The Virginia Tech scientist have proven that this will also work for cancer treatment and is now being implemented in 3.4% of clinical trials that consider the circadian rhythm.

While the proportion of clinical trials is still too small, we might see great advancement in cancer treatment and patients’ wellbeing in the near future.

In the meantime, remember that you can reduce cancer risk by sleeping well, avoiding artificial lights at night and being mindful of your master clock!


Additional Readings

The Pathophysiologic Role of Disrupted Circadian and Neuroendocrine Rhythms in Breast Carcinogenesis

Chronotherapy: Intuitive, Sound, Founded…But Not Broadly Applied

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