Why Insomnia May Raise Stroke Risk While researchers don’t completely understand why insomnia may increase stroke risk, Vignatelli offers a few potential explanations. It’s possible that persistent sleep trouble puts the body into a constant stress response, he says, overactivating the same systems involved in a fight-or-flight reaction. That raises blood pressure, heart rate, and tension in blood vessel walls. As a result, the stress hormone cortisol stays elevated, which can raise…