A reader asks:

I work in rotating shifts: two days of 7 AM – 3 PM, then two days of 3 PM – 11 PM, then two days of 11 PM – 7 AM before taking a break. Then I take four to five days off to recover. Not unexpectedly, I have a low energy level, and feel foggy, for three to four days during normal daytime hours. I also have difficulty falling asleep at my usual bedtime of 10 – 11 PM. Do you think a light exposure strategy would be of help to readjust more quickly back to a circadian rhythm appropriate for 8 AM – 11 PM life? I really need to restore concentration and energy!


Rotating shift work is a bane of today’s industrial society. You are being forced into a work-rest pattern that our natural body function cannot support. Beyond problems with concentration and energy, in this can create and sustain serious depression in some people.

It would be far easier to adjust to a long-duration night shift than to the kind of rotation you describe (with unsatisfying “recovery” days off), because then the circadian rhythm in your body could shift to a consistent new phase, analogous to living in a different time zone. The likely reason you are finding it difficult to flip into daytime mode on your days off is that the rotating shift (with rotating light-dark exposure) causes a lagging effect in your circadian rhythm relative to local time.

Under these conditions, if you were to use light therapy to maintain a day-appropriate rhythm, you would find yourself drowsy during work shifts and incapable of full restorative sleep during the day. So we have a situation with no clear solution that also poses a serious public health issue.

You might experience partial benefit using controlled-release doses of melatonin at 10 PM on days off to prepare you to sleep, since your internal melatonin cycle is likely several hours delayed. After taking melatonin, you should avoid intense physical activity and remain in a dimly lit but visually comfortable environment until you become sleepy. In addition, you might gain a significant daytime energy boost with a high dose of light therapy (say, 60 minutes at 10,000 lux) upon awakening, even if it is later than 8 AM. Obviously also, do your best to resist napping, which can make it more difficult to fall asleep earlier at night.