• Dr. D

Bright light therapy and sleep


Waking too early in the morning


The patient, 81 year-old Mrs. A., told me she wasn’t sleeping as she should. She routinely woke up at 3AM and then wasn't able to get back to sleep. It's lonely in the middle of the night, she explained, television isn't very good at that hour, and she wanted to wake up much later.


This is a common issue for older adults. A google search comes up with hundreds of sites suggesting how to remedy the problem of early morning wakening. The advice that's given is generally the same. However, in almost all cases,

the writers forget to ask a crucial question; what time do you go to bed?


In the case of the patient above, the answer was 7 PM. In other words, she was getting a full eight hours of sleep by 3 in the morning.


I explained to her that her body was telling her she didn’t any more beauty rest. There was no medication or herb I could give her that would help her sleep longer.


If she wanted to snooze later in the morning, she would need to go to bed later at night.


Sleep disturbance – common in older adults


Many factors contribute to sleep problems in older people: breathing trouble, heart issues, pain, anxiety, are only a few of the possibilities.


Here I’m only going to focus on one of the possible causes, one that can be helped with bright light therapy (BLT). Bright lights can change the time the body releases chemicals that regulate sleep and wakening. This is called the “circadian rhythm.”

Circadian rhythm – what is it?


The word ”circadian” comes from two Latin words that translate to “about a day.” It refers to the biological time clock that regulates what happens to our bodies over a period of about 25 hours.


Two body chemicals that change as a result of the time of the day are cortisol and melatonin. Cortisol levels are up in the daytime while melatonin is down; the darkness of night is the opposite, with cortisol down and melatonin up.


We know that cortisol helps with activation in the daytime, while melatonin promotes sleep.


Bright light therapy – what is it?


In a (previous blog https://www.sjdpsych.com/post/bright-light-therapy-and-sleep) I described bright light therapy (BLT) at some length and won't repeat all of it. Briefly, BLT uses a broad-spectrum light situated so that it shines on the person’s retinas.


BLT uses light that is of adequate strength and has all the different kinds of wave lengths -green, purple, blue, etc – without the burning rays.


The strength or intensity of light is measured in lumens; 10,000 lumens is best for BLT. To give you an idea – a 100 watt incandescent bulb is about 1500 luxe.

Bright light therapy may change the circadian rhythm

BLT is used for a variety of conditions, including depression and sleep disorders. For the person treating their mood with BLT, I suggest they use it ins the morning.


Use later in the day can result in sleep problems because BLT alters circadian rhythm; it changes the time when cortisol and melatonin are at their highest and lowest levels. We exploit this “side effect” for the person with a sleep issue.


Science has shown that the circadian rhythm's melatonin (sleep) phase occurs earlier in older adults than in younger ones. This contributes to older people’s need to go to bed earlier.


High intensity bright light can push melatonin levels down and cortisol levels up for a few hours, changing the sleep/wake cycle.


For someone like Mrs. A, I suggest she use BLT in the early afternoon. After only a few sessions, they will typically find that they don’t want to go to bed as early and can sleep later.

Enlightened about sleep

Mrs. A started using the BLT at about noon. With this she did sleep later, but was still getting up earlier than she wanted.


I had her experiment with the timing of the BLT to see what time she needed to use it in order to stay asleep as late as she wanted. Using her light for half an hour around 2PM made it possible for her to go to bed around 9 PM and get up at 6AM. She was happy with that.

Reminders about BLT and sleep


1. Changes in sleep patterns are common and distressing in older age

2. BLT can help with some sleep disturbances, but it must be the appropriate kind of light given at the correct time of day

3. Bright Light Therapy is a natural approach to some types of sleep problems.


Image of distressed woman by: © Can Stock Photo Inc. /dolgachov

Image of field with daylight by: © Can Stock Photo Inc. /tobkatrina