Warning: Bright light at night may cause cancer

Startling new data show that too much artificial light at night may be detrimental to one’s health. This intriguing possibility comes from several studies showing higher cancer and obesity rates in people exposed to bright lights at night.

As the scientific evidence grows, the World Health Organization has already concluded that working during the night shift is probably carcinogenic (cancer-causing). Take note: People who work at night are particularly at risk, especially call center agents, entertainers, and night-shift workers.

According to lead researcher Professor Abraham Haim at the University of Haifa, the culprit is chronodisruption or the disruption of one’s body clock.

Professor Haim explains that the brain’s pineal gland (a tiny organ at the center of the brain) produces melatonin in the absence of light at night. Hence, when you are exposed to bright lights during the night, your brain produces less melatonin. Low levels of melatonin have been linked to bad health effects such as inflammation, weaker immune system, and faster cancer growth.

Just consider: This so-called light pollution could be an emerging public health problem in developed countries. Based on earth surface photographs taken from space, we see that the areas of darkness are slowly disappearing. More and more, the bright lights of urbanization have invaded people’s lives.

Let us look at medical problems that have been linked to light at night:

  • Increase in prostate cancer. Research conducted by Professor Haim and Professor Richard Stevens of the University of Connecticut studied the incidence of three types of cancer (specifically prostate, lung, and colon cancers) in men in 164 countries. Data on cancer incidence were gathered from the records of the International Agency for Research on Cancer. On the other hand, light at night (LAN) data were collected from satellite images from the Defense Meteorological Satellite Program. For the study analysis, the countries were divided into three categories: countries with high LAN exposure, countries with medium exposure, and countries with low LAN exposure. The results show that countries with high LAN exposure had the highest incidence of prostate cancer at 157 prostate cancer cases per 100,000 people. In comparison, countries with the lowest LAN exposure had only 67 prostate cancer cases per 100,000 people (50% less). Although this study is by no means definitive, it shows a curious link between light at night exposure and prostate cancer. This study supports the theory that suppression of melatonin increases cancer risk.
  • Increase in breast cancer. Several epidemiologic studies done in Denmark and the US have shown an increase in the incidence of breast cancer among female night-shift workers. This correlation between LAN and breast cancer was tested in the laboratory in 2005, which showed that exposure to artificial light at night enhanced the growth of breast tumors.
  • Increase in obesity. Aside from getting cancer, a US-Israel study showed that exposure to bright lights at night may cause obesity. In laboratory studies, Ohio State neuroscientist Dr. Randy Nelson and Professor Haim showed that mice exposed to 24 hours of constant daylight gained more weight compared to mice exposed to only 16 hours of daylight. After eight weeks, the mice exposed to constant light had 50% weight gain compared to the other group. Dr. Nelson observes, “Something about light at night was making the mice in our study want to eat at the wrong times to properly metabolize their food.”

The researchers also believe that disruption in one’s body clock and lack of sleep can make people eat more often and at the wrong times. Dr. Nelson adds, “Light at night is an environmental factor that may be contributing to the obesity epidemic in ways that people don’t expect.”

Here are some tips to get your body clock working perfectly. This can translate to more energy and better health.

• Sleep at around the same time every night and wake up at the same hour. This technique will keep your body clock in harmony.

• Limit your light exposure at night. It’s not scientifically proven yet, but you can try to avoid very bright lights at night, especially within three hours of bedtime.

• Limit computer time at night, maybe less than half an hour. When you sit in front of the strong glare of the computer screen, this could suppress your body’s melatonin production.

• Although exposure from watching TV is only minimal, make sure you sit several feet away from your TV set.

• In your bedroom, draw up the window curtains to limit glare from the streets.

• Use yellow or red light instead of white light at night. According to George Brainard, a professor of neurology at Jefferson Medical College in Philadelphia, temporarily turning on a bright white light at night during your bathroom visit may disrupt the production of melatonin.

• Melatonin supplements may be useful in certain cases. According to Professor Brainard, “Night shift workers might consider taking a supplement right before they go to sleep in the morning. Those who travel internationally can try it to reset their body’s clock and avoid jet lag.” Consult your doctor about this.

• Be exposed to sunshine during the day. Early morning sunshine is best and it activates the body’s natural rhythm.

• During the day, get exposed to indirect sunlight. Avoid staying in a dark room all day. The purpose of this “light at daytime” and “dark at night” routine is to make sure your body knows when it is day (time to work) and when it is night (time to sleep).

Lastly, what about people who sleep with the lights on, kids who play computer games at night, and people who gamble all night? Are these harmful habits or not?

We’re not sure. There is still no clear data on how much light at night is harmful. For the present time, I suggest you watch out for this probable health hazard: bright lights at night. Willie Ong MD

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