Blood pressure normally reaches its lowest level (dips) during sleep. However, some people with high blood pressure have little or no decline in blood pressure while sleeping, which has been linked to an increased risk for heart attack and stroke. Findings from a large study of hypertensive patients show that "non-dippers" have higher levels of the clotting factor fibrinogen, which could account for at least part of the increased risk.
"To my knowledge, the rise in fibrinogen in non-dippers has not been reported before," says Ramon C. Hermida, Ph.D., lead author of the study and a professor at the University of Vigo in Vigo, Spain. "The results emphasize the importance of adequate blood pressure control throughout the day. Our findings also show that identification of non-dippers is very relevant to prevention of coronary events and death."
Hermida said data from the U.S. National Myocardial Infarction Registry, a large database on heart attack patients, have shown that a 75 mg/dL rise in fibrinogen translates into an 85 percent increased risk for coronary events and mortality.
"Even within the range of normal levels, a 75 mg/dL increase in fibrinogen is very relevant to the risk of coronary events and death," he says. "This is not just a small change but a major increase in risk."
The study also confirmed previous research showing that fibrinogen levels vary over the course of a year and peaks during winter months. The winter peak in fibrinogen levels correlates with annual patterns of coronary events and mortality, which also peak during the coldest months. Several studies have documented elevated fibrinogen levels as a risk factor for heart attack, Hermida notes.