If you find it harder to get out of bed in February than June, you probably aren’t imaging things. Here are seven statistics related to winter tiredness.

Here are seven statistics related to fatigue during the winter months:

1. Daily exposure to 30 to 90 minutes of blue or short wavelength light during dark winter mornings is as effective as taking antidepressant drugs in treating seasonal affective disorder, a form of depression that affects some people during the winter. (Daniel Kripke, Journal of Affective Disorders)
2. Exposure to sunlight increases your body’s production of serotonin, thereby brightening your mood. One way of getting more sun exposure is to park your vehicle as far as possible from work, stores, or other places, so that you are forced to walk in sunlight for a few minutes.
3. Here is one cause of insomnia that you may not have considered: Waking up at night and turning on a bright light, even for a short time, can make it difficult to return to sleep quickly. (Adam Fletcher, organizational psychologist and expert on fatigue and sleep loss)
4. Exercising after work has two benefits: It can reduce early evening tiredness during the winter months and it can also improve sleep quality. (National Health Service, UK)
5. Increasing consumption of these two things in your diet during the winter months will leave you feeling more alert and energetic: fruits and vegetables. (National Health Service, UK)
6. In the winter, when daylight hours are short, your body produces more melatonin, a hormone that makes people sleepy.
7. If you are feeling fatigued at the end of your work shift and need to drive home in cold weather, here is one thing you should know: Blasting the heat in your vehicle could lull you into an unintended sleep while you are behind the wheel.

If you find it harder to get out of bed at 6 a.m. in February than in June, you probably aren’t imagining things. Dr. Michael Terman, a sleep disorder specialist at Columbia University Medical Center, says about 50 percent of North Americans feel foggy and dragged out for the first few hours after awakening in winter darkness. He says workers are more prone to making errors and suffering injuries while they are in this state of grogginess.