A study has found that not blocking the light before going to sleep at night can put the body in a “warning state,” increasing heart rate to nearly daytime levels. This was a risk factor for adverse health outcomes, including cardiometabolic diseases such as diabetes and heart attack, the study added.
The research, published in PNAS, was conducted by scientists at Northwestern University in Illinois.
They studied a group of 20 adults exposed to moderate light at night to understand its harmful effects on the body.
Half of the participants had to sleep one night in a dimly lit room, followed by another night’s sleep in moderate light. The other 10 adults slept in low light for two consecutive nights.
Measures of Insulin Resistance (Morning Homeostatic Model Assessment of Insulin Resistance, 30 Minutes Insulin Area Under the Curve [AUC] of a 2-hour oral glucose tolerance test) were higher in the room with light versus dimmed light,” the researchers said in the study.
Insulin resistance is when the cells of the body fail to respond to the sugar-regulating hormone and cannot use the glucose on the body.
The study also said that the group that slept in moderate light had an increased heart rate compared to those in the low light group.
The researchers said disruption of the normal cardiovascular pattern could be bad news for heart health because it doesn’t get the restorative break it needs at night.
The moderate light condition for the study participants was defined as 100 lux, an international unit of illumination.
One lux is the amount of light produced by one candle, measured from one meter away. In most homes and offices, the light volume is usually between 50-500 lux.
The adults who took part in the study were between the ages of 18 and 40, had a usual sleep duration of 6.5 to 8.5 hours and usually started sleeping from 9:00 pm to 1:00 am.