A new research study provides additional evidence that lack of sleep may increase a person’s risk for heart disease. In the study, conducted at the University of Chicago, researchers assigned 26 healthy young adults to a sleep restriction pattern of five hours per day for eight consecutive days. They found that lack of sleep was associated with increased heart rates. In addition, the researchers linked insufficient sleep with an increase in levels of a stress hormone called norepinephrine, which is capable of raising blood pressure. The study, published in the journal Hypertension, was partly funded by NHLBI.