Your brain senses trouble and tells your body to release adrenaline-like substances into the bloodstream the so-called fight-or-flight reflex which increases blood pressure, thus the link to sleep apnea and high blood pressure.
These have the virtue of being more clear-cut than friendships (did you sleep together or didn't you?) andthus what is or is not a link between nodes is unambiguous.
With devices like these a health insurance company could offer you discounts for keeping your stress level low, eating healthy, getting more sleep, and generally engaging in behaviors that make you healthier andthus cheaper to insure.
Many researchers hold almost precisely the opposite opinion that sleep serves to re-activate synapses that were strengthened during the day, andthus reinforces their strength rather than diminishing it.