NONLINEAR TRANSCRANIAL DOPPLER ANALYSIS DEMONSTRATES AGE-RELATED-CHANGES OF CEREBRAL HEMODYNAMICS

We studied the age- and gender-related changes in complexity of arteri al blood flow by analyzing the maximum velocity waveforms, Data were c ollected by insonation of the middle cerebral artery blood flow by a 2 -MHz transcranial pulsed Doppler system, Following the paradigm of non linear dynamical systems or ''chaos'' theory, complexity is best evalu ated by estimating the correlation dimension (D-2) and the largest Lya punov exponent (lambda(1)), Forty healthy persons (male/female ratio: 1/1; mean age 48.6 y; range 19-86 y) were studied, No gender-related d ifferences were observed, The age-effect showed a diminishing lambda(1 ) [df(1, 36) = 5.687; p < 0.022] and an increasing D-2 at higher age [ df(1, 36) = 4.997; p < 0.032], The age-related decline of the lambda(1 ) implies a more prominent periodicity, explained by reduced fluctuati ons in R-R intervals and an altered gain of the baroreceptor reflex, T he increased D-2 might be related to more prominent vessel wall oscill ations due to the increased vessel wall stiffness at higher age.