Do not fear The Darkness!

The irony of me reading this in bed while also trying to fall asleep, has made me leave this comment and stop scrolling for the night.

unfortunately, the study included information about intensity of night time light but did not included information about the sources of light

So I guess it's user-interpreted intensity

For heart attack, for example, compared with those in the darkest 50th percentile, those who experienced some nighttime light — in the 51st to 70th percentile — had a 20 percent increased risk of heart attack.

Those who experienced more light, in the 71st to 90th percentile, had a 27 percent increased risk.

And those who experienced the most nighttime light, in the 91st to 100th percentile, had a 47 percent higher risk.