What My 3 a.m. Phone Habit May Be Doing to My Brain

Deborah Kan is an award-winning journalist and founder of Being Patient. In this “Thought of the Week” column each Friday, she highlights one of the key stories shaping the future of brain science. 

Dear readers,

I’m guilty. When I wake in the middle of the night, the first thing I do is reach for my phone. I tell myself the scrolling settles me, that it helps me drift back to sleep, and some nights it seems to work. I have done it for years but in the back of my mind, I know that I shouldn’t be reaching for my phone. 

Dr. Em Wong, an internal medicine physician who writes for Being Patient about brain health, wrote for us this week why all memory loss is not dementia. One point that resonated profoundly with my own habits was that most of what we call forgetting, she explained, is not memory loss at all. It’s distraction. We have all walked into a room and forgotten why because the memory was never recorded in the first place. We were not paying attention. Staying up late to scroll, she wrote, may further impair cognition.

(Yikes! I read that twice.)

So I did a bit of research to understand what is actually happening when I pick up the phone at 3 a.m. The screen is not just keeping me company. Its light is short-wavelength and blue-heavy, and that kind of light tells the brain it’s daytime. A team at Brigham and Women’s Hospital led by Anne-Marie Chang showed that reading on a glowing screen in the hours before sleep suppresses melatonin, the hormone that ushers us into rest, pushes the body clock later, and cuts into REM sleep. The people in her study fell asleep more slowly and woke up less sharp the next morning, even when they spent the same hours in bed.

The reason that matters goes deeper than feeling groggy. Sleep is when the brain does its housekeeping. While we rest, it clears out metabolic waste, including beta-amyloid, the protein that clumps into the plaques found in Alzheimer’s. In a small study at the National Institutes of Health, researchers scanned the brains of healthy adults after a normal night, then again after a single night with no sleep. After the lost night, amyloid had risen in the hippocampus and the regions around it, the very part of our brain that Alzheimer’s attacks first. It was a small study and just one night involving 20 people but the direction was hard to ignore.

Over a lifetime, the pattern holds. Following nearly 8,000 people for 25 years, researchers at University College London found that those who slept six hours or less in their 50s and 60s were about 30 percent more likely to develop dementia than those who slept seven. Note that this is an association and not a verdict. It is possible that the earliest disease was disrupting their sleep rather than the reverse, and the researchers said exactly that but the thread running through all of it is the same. The brain needs sleep to protect itself, and we keep finding new reasons it is true.

To clarify what I am and am not saying: No one has shown that scrolling at 3 a.m. gives you dementia but scrolling can delay and fragment sleep, and most notably reduces REM, the stage important for clearing cellular waste. 

In my view, the phone at 3 a.m. is not the villain. The lost sleep is. The phone just makes the loss easy to choose. I am going to try to put my phone in the next room at night time for a week. I know…easier said than done!

With hope,
Deborah