Light therapy may cut sleepiness and move the body clock in shift workers.

The review

1. 01

   Who took part

   656 people took part, mostly shift workers or people on simulated shifts. They were about 32 years old on average, and about 43 in 100 were women.

2. 02

   What they did

   People got light therapy at different brightness levels, for different total times. It was given at night or during the day. Comparison groups had dim light, room light, placebo capsules or no active treatment.

3. 03

   What happened

   Light therapy reduced sleepiness and shifted the body clock more than other groups did. Medium brightness for a shorter time reduced sleepiness more; brighter light shifted the body clock more, but the best length is unclear. Many studies were weak, and a test found signs that some weaker results were not published.

What the review found

1. Helped

   Shift workers who had light therapy felt less sleepy than the other groups did.

   Pooled analysis of 15 studies · vs dim or room light, placebo capsules or no treatment · they rated themselves · ⚠ most studies had serious flaws; signs that small negative studies went unpublished

2. Helped

   Shift workers who had light therapy shifted their body clocks more than the other groups did.

   Pooled analysis of 13 studies · vs dim or room light, placebo capsules or no treatment · ⚠ most studies had serious flaws; results look too good to be true

Source