Clue to High Heart Attack Risk in Morning Found
 (HealthDayNews, 6/1/04)

When Dr. Virend Somers of the Mayo Clinic, and team, measured endothelial function of 30 healthy nonsmokers at bedtime, 6 a.m. and 11 a.m, the scientists found a 40% decrease in endothelial function in the early morning that rebounded to normal by later morning. The endothelium, composed of cells that line the blood vessels, facilitates expansion and contraction to maintain a balance of blood pressure and blood flow. The researchers speculate that the early morning reduction in vessel flexibility could account for the fact that most heart attacks and stokes occur at this time of day.