The connection between sleep and lung cancer

Getting a good night’s sleep is important to our overall health and well-being. Sleep improves our brain function, enhances our mental health, boosts our immune system, strengthens our heart, and according to one study, may help us ward off lung cancer.

The study was recently published in the Science Advances journal and found a link between disrupted sleep patterns — which can throw off circadian rhythm — and lung cancer. Circadian rhythm is our body’s 24-hour internal clock that regulates cycles of alertness and sleepiness and aligns with the light of daytime and darkness of night. It also provides the stable and restorative sleep we need to stay healthy.

“There has been epidemiological evidence to suggest disrupted circadian rhythm increases risk of cancer,” says Dr. Kai Zu, a board-certified oncologist and hematologist affiliated with Sharp Grossmont Hospital’s David & Donna Long Cancer Center. “But this study takes it a step further in explaining the mechanism of how disrupting circadian rhythm promotes development of cancer.”

Disrupted sleep triggers tumor growth in lungs
Based on the findings, when our circadian rhythm is disrupted, it affects a gene called HSF1 that can trigger tumors. The study’s scientists used mice that were injected with a virus that could promote the growth of tumors, and divided the mice into two groups.

The first group of mice was exposed to a typical light cycle of 12 hours of light and 12 hours of darkness. The second group was exposed to a light cycle similar to what shift workers experience, where the light hours were moved earlier by eight hours every two or three days. The study found that mice exposed to the irregular, shifting light patterns had an increased amount of tumor in their lungs when compared with those exposed to the 12 hours of light and 12 hours of darkness.

Although the study used mice and not people, Dr. Zu says it is still a good predictor of human outcomes. “Animal models are extremely valuable in studying human cancers,” he says.

However, Dr. Zu notes that lung cancer is not a singular entity, and its causes vary greatly. Nonetheless, these findings help shape our understanding of how circadian rhythm can impact cancer and potentially, how we might protect vulnerable groups who are at risk.

For example, there have been numerous studies indicating that shift workers and others with disrupted sleep schedules have higher rates of cancer. While more research is needed, some researchers foresee a time in the future when medications targeting the HSF1 gene in individuals with ongoing circadian rhythm disruptions could potentially prevent lung cancer. This could help millions of shift workers — police officers, firefighters, nurses, doctors, pilots, food servers, truck drivers and many more professionals — who are at increased risk.

Lung cancer risk factors
Lung cancer causes more deaths in the U.S. than any other type of cancer in both men and women, making up almost 20% of all cancer deaths. Each year, more people die of lung cancer than of colon, breast and prostate cancers combined.

According to Dr. Zu, cigarette smoking remains the No. 1 risk factor for lung cancer. “Your risk also increases with both the number of cigarettes smoked per day and the duration of cigarette smoking,” he says. “Other factors, including air pollution and second-hand smoke, have been associated with risk of lung cancer in nonsmokers.”

The good news is innovative research, such as this study, and medical advances are continually giving us new insight and better tools to help lung cancer patients.

“Over the last 10 years, lung cancer outcomes have improved tremendously,” Dr. Zu says. “We’ve learned that approaches we may have taken in the past are outdated, and new research is continually evolving in the field of molecular therapy and immunotherapy, leading to more targeted, cancer-inhibiting drugs for much improved outcomes.”

Get screened
Unfortunately, lung cancer doesn’t always present signs or symptoms in the early stages. That’s why screening is so important. And like all cancers, it’s best to detect it early when it’s most treatable.

If you smoke, talk with your doctor about your individual risk factors and if screening is right for you. The American Cancer Society recommends yearly low-dose lung CT scans for people ages 50 to 80 who currently smoke or formerly smoked and have a 20 pack-year or more smoking history — meaning, they smoked an average of one pack per day for 20 years or two packs a day for 10 years.

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For the news media: To talk with Dr. Kai Zu, board-certified oncologist and hematologist about lung cancer for an upcoming story, contact Erica Carlson, senior public relations specialist, at erica.carlson@sharp.com.