Insomnia in colder months due to lack of sunlight and vitamin DSome people have trouble sleeping when the days get shorter. I’m one of them and so is Gabriel, who recently wrote in wondering how to improve his sleep:








I was born close to the equator in Brazil, and I usually don’t have problems sleeping when I’m there or during the summer time in Canada, where I live now. But winter is around the corner, and my sleeping problems have just begun again. I usually go to bed at 11 p.m. but wake up around 3 a.m. However, in the summer my wake time is 7 a.m. I feel irritated, depressed and cannot concentrate. . . Is light treatment the way to go?

Lack of Bright Light

Reduced light exposure probably accounts for Gabriel’s symptoms, including his insomnia at night. People who live in northern latitudes (residents of Canada fit the bill) get less exposure to sunlight starting in the middle of fall and continuing through March or April. This can alter circadian rhythms and destabilize sleep. It may be related to seasonal affective disorder (SAD).

Especially susceptible are those who commute in the dark and work all day in windowless offices, dimly-lit warehouses, and the like. Sunlight resets the body clock to run on a 24-hour cycle. Without daily exposure to sunlight (or to the blue-enriched light emitted by a light box), circadian rhythms may go out of sync. Secretion of the sleep-friendly hormone melatonin may be delayed in the evening. (Or, as I suspect in my case, it may begin too early, causing me to drift off and—like Gabriel—wake up too early.)

Sleep-related symptoms vary from person to person, but here are some you might recognize in yourself:

  • Sleeping more or less than usual
  • Trouble falling asleep or a tendency to fall asleep earlier than normal
  • Having an erratic sleep schedule
  • Trouble getting out of bed
  • Feeling groggy in the morning and tired during the day

Increase Your Exposure to Bright Light

Getting a healthy dose of exposure to sunlight every day may solve the problem. Take a walk outside or move your desk to the sunny side of the room.

Light treatment with a light box can also work. Light emanating from a light box mimics the blue-enriched light from the sun. Set it up so the light floods your work space but you’re not looking directly into it: this will likely increase your alertness and help stabilize your sleep. The amount of light exposure needed varies from one person to the next.

Get Enough Vitamin D

Another thing to consider is taking vitamin D supplements. Emerging evidence suggests that lack of the sunshine vitamin may contribute to insomnia and sleep problems in the wintertime, when the days are shorter and more overcast. The latest study published on this topic appeared last February, and the results strongly suggest that sufficient levels of vitamin D are important to maintaining healthy sleep. Among over 3,000 men ages 68 years and older,

  • lower serum vitamin D levels were associated with higher odds of short sleep duration (less than 5 hours a night), and
  • the sleep of men with low levels of vitamin D was less efficient.

The human body produces vitamin D with exposure to sunlight. So people living in northern latitudes are more likely than others to develop a vitamin D deficiency in the wintertime. Other risk factors for vitamin D deficiency are these:

  • Being female or older
  • Being obese or underweight
  • Having a physically inactive lifestyle
  • Having dark skin (The pigment melanin reduces the ability of the skin to manufacture vitamin D with exposure to sunlight.)

While the relationship between sleep and vitamin D is not fully understood, existing research suggests it’s probably a good idea to take a supplement, especially if during the colder months your sleep takes a turn for the worse. The Institute of Medicine recommends 600 international units (IUs) daily for people up to 70 years old and 800 units for people 71 years and older. But the safe upper limit for vitamin D is currently 4,000 IUs a day.

Do you have trouble sleeping in the colder months of the year? If you’ve tried using a light box, has it helped?

Posted by Lois Maharg, The Savvy Insomniac

Lois Maharg has worked with language for many years. She taught ESL, coauthored two textbooks, and then became a reporter, writing about health, education, government, Latino affairs, and food. Her lifelong struggle with insomnia and interest in investigative reporting motivated her to write a book, The Savvy Insomniac: A Personal Journey through Science to Better Sleep. She now freelances as an editor and copy writer at On the Mark Editing.


  1. Well, I knew about the light but I didn’t know about the vitamin D. I think I’ll start the supplement now.



    1. I hope the vitamin D helps, Eric. If it does help stabilize your sleep, please check back in and let us know.



  2. I hate winter because that is probably my sleepless season during my outstation years. (*I am from 1-season country (summer only…)- Singapore)

    Light box is one of the tools I used. Sometimes it helps. Sometimes it doesn’t work for me. Hmm, 50-50… I can say. For me, it is not so much about the light thing.. the coldness makes me worried more (during bedtime). Not sure of anyoen out there have this experience. It is weird to me, I don’t know why.

    Maybe I associate coldness with some negative emotions such as loneliness, unsafe, getting stuck (freezing).



    1. Hi West,

      Thanks for sharing your comments about the light box. I use a light box too, with mixed results. Sometimes it helps. Other times, not so much.

      Your comment about coldness is intriguing. Sleep usually begins as people’s internal temperature starts to drop. A cool bedroom can facilitate that process. So people are usually advised to turn the thermostat down at night to keep the bedroom a little cooler than is comfortable during the day.

      Temperature extremes are never conducive to sleep, though. And being too cold could very well give rise to negative emotions. I hope wherever you are now that you’ve got plenty of warm blankets!



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