I had sleep apnea for years, which a study eventually categorized as "moderate to severe", and while I wasn't operating on four hours of sleep, I didn't feel to

I had sleep apnea for years, which a study eventually categorized as "moderate to severe", and while I wasn't operating on four hours of sleep, I didn't feel too bad either. I didn't even drink coffee. When the brain notices it's starting to suffocate and jolts one into waking up enough to recover from an apnea event, it releases a small amount of cortisol, dozens or hundreds of times per night. That's the source of the long-term cardio risk, as I understand it.