If you didn’t sleep well last night, it might be residual exhaustion from the time change.  But if you don’t sleep well in general, could this be why?

A new study out of Northwestern found that sleeping with even a LITTLE bit of light is bad for us.  It really doesn’t take much.

Researchers monitored people while they slept.  They recorded their heart rate and breathing, hooked them up to an EKG, and watched their brainwave activity.  They also had them hooked up to an I.V. to draw blood while they slept.  (With that going on, it’s amazing they fell asleep at all.)

Everyone slept in the dark the first night.  Then some slept with a dim overhead light on the second night.  It was about as bright as a streetlight coming through your window.

They found that when ANY lights are on, your heart rate climbs, and it raises your blood sugar.  Both are bad, because an elevated heart rate at night has been linked to heart disease and early death.  And high blood sugar can lead to diabetes.

They were surprised at how even a tiny bit of light made a difference.  Only about 5% of light makes it through when our eyelids are closed.  But the study even talks about how light from a TV could cause issues.

The lead author says that to make sure you get a good night’s rest, you should turn off all the lights, close your curtains, and think about using a sleep mask.