Correlates of middle cerebral artery blood velocity in the elderly

We analyzed the association between hematologic factors and blood velocity of the middle cerebral artery in 42 healthy ambulatory subjects aged 63-86 years. We found a significant inverse association between mean velocity and both hematocrit (r = -0.37, p less than 0.02) and fibrinogen concentration (r = -0.42, p less than 0.005). These two variables are independently associated with velocity and together explain 29% of the variance in mean velocity. Both hematocrit and fibrinogen concentration should be considered in the interpretation of transcranial Doppler findings in this population.