Lights on or lights off? When I first heard TV host Boy Abunda ask his guests this question, I naively thought he meant sleeping the whole night with the lights on or off.

I would have invited him to help in one of our advocacies to make the public aware that sleeping at night with the lights on or with some source of light from outside the window—like a street lamp post—can be bad for the health.

It may increase one’s risk of having breast, colon or prostate cancer.

Night-shift workers

There is research data indicating that night-shift workers, such as doctors, nurses, security guards, police officers and perhaps, call-center workers have a significantly higher risk of developing cancer.

There are also some published data suggesting that women residing in areas with high levels of external light at night, such as streetlights, appear to have a higher risk of breast cancer.

Night light exposure has also been linked to obesity, diabetes, high blood pressure and other heart diseases.

TV on

Some fall asleep with the TV on, which is not a healthy practice. Repeated exposure to blue light at night, emitted by the TV set, electronic gadgets and the energy-efficient LED lightbulbs, may cause some long-term harm.

There are now eyeglasses or “night shades” that specifically block blue light to be used for night work.

Why does exposure to nighttime light affect our health adversely?

Hormonal balance

It’s related to the disruption of the hormonal balance in our body. Originally, the sun was our major source of lighting and nights were spent in relative darkness except for a faint light from the moon.

Our bodies were designed for this original day-and-night pattern of lighting.

With all the artificial illumination we now have, nights can be like days and this disturbs the body’s biological clock, called the circadian rhythm.

The common pathway, as suggested by most research, is that exposure to light suppresses the secretion of melatonin, a hormone that modulates our circadian rhythm.

With ample melatonin levels, we get longer and deeper sleep. If we have low melatonin levels, we sleep shorter hours, with a lower quality of sleep.

Some research data suggests that lower melatonin levels might explain the association with cancer.

Aside from possible increased cancer risk, another study done at Harvard also suggested a possible connection of night exposure to lights to diabetes and obesity.

Subjects with disrupted circadian rhythms due to light exposure at night had higher blood sugar levels and lower levels of leptin, a hormone that makes one feel full after a meal, making one stop eating.

Table lights

Stephen Lockley, a Harvard sleep researcher, wrote that even dim light emitted by table lights can interfere with a person’s circadian rhythm and impair melatonin secretion.

Dr. Lockley’s group has also done research linking short and poor quality of sleep to increased risk for depression, as well as diabetes and cardiovascular problems.

Here are seven ways to maintain a healthy circadian rhythm of our body:

Maintain darkness

1) Install blackout shades or heavy drapes on your bedroom windows to maintain the darkness in your room at night.

2) Cover your eyes with dark shades, like the masks the airlines give during long-haul flights.

3) Avoid looking at bright screens at least one hour before going to bed.

4) Use the lowest wattage or red bulbs in nightlights (red light has the least power to shift circadian rhythm and suppress melatonin).

5) Avoid turning on the bright lights if you wake up at night.

6) If you’re a night-shift worker or use a lot of electronic devices at night, wearing blue light-blocking glasses or installing an app to filter the blue/green wavelength at night can help minimize blue light exposure.

7) Get ample sunlight during the day since this will also help enhance your sleep at night.