Sleep. Short and poor-quality sleep are both associated with raised blood pressure (40). On the other side of the spectrum, excessively long sleep may also be harmful. One study found increased blood pressure in those who got fewer than five hours of sleep per night and in those who averaged more than nine hours of sleep per night, when compared with people who slept around seven hours (41). I suspect that it’s not the long sleep itself that is the problem, but that some underlying condition is both increasing sleep requirement and raising blood pressure.