[WD-101000]

> It's going to be fascinating if there's a mechanism by which sleeping with light can cause heart disease.

I suspect everyone in the field already knows the top-level answer: light at night blunts the output of the circadian pacemaker (SCN), with all sorts of downstream effects including control of various hormones. So the levels will be different with light at night. "at night" means biological night. If someone consistently sleeps on some schedule with bright enough light during their awake time, and it's dark during their sleep time, it's fine.

I'm not in the field. I read up on it at one point at a shallow level and talked to some researchers about it informally.