A study has said that failing to block out light before going to sleep at night could put body in an “alert state”, elevating the heart rate to near daytime levels. This implicated as a risk factor for adverse health outcomes, including cardiometabolic disease like diabetes and heart attack, the study added.
The research, published in PNAS, has been carried out by the scientists from Northwestern University in Illinois.
They studied a group of 20 adults who were exposed to moderate light during night time to understand the harmful effects it can have on the body.
Half of the participants were made to sleep one night in a dimly-lit room, followed by another night’s rest in moderate light. The other 10 adults slept in dim light conditions for two consecutive nights.
“Measures of insulin resistance (morning homeostatic model assessment of insulin resistance, 30-min insulin area under the curve [AUC] from a 2-h oral glucose tolerance test) were higher in the room light versus dim light condition,” the researchers said in the study.
Insulin resistance is when the cells of the body do not respond to sugar-regulation hormone and can’t use the glucose on the body.
The study also said that the group which slept in moderate light conditions had an increased heart rate, compared to those in the dim light group.
The researchers said that disruption in normal cardiovascular pattern could be bad news for heart health as it doesn’t get the restorative break needed during the night.
The moderate light condition for the participants of the study was defined as 100 lux, an international unit of illumination.
One lux is the volume of light produced by one candle measured from one metre away. In most homes and office the volume of light is typically between 50-500 lux.
The adults who took part in the study were between the age of 18 and 40 years, had a habitual sleep duration of 6.5 to 8.5 hours and habitual sleep onset of 9:00 PM to 1:00 AM.