BLOOD FLOW IN FACIAL SKIN 503 Wa Wp Wa is the most commonly used international parameter of roughness. It is the arithmetic mean of the departures of the profile from the mean line. Wa= 1--Lf•]• Wp is the ma•mum height of the profile above the mean 1/ne within the assessment length. Wq Wq is the ms parameters corresponding to Wa. Wt Wt is the ma•mum peak to valley height of the profile in the assessment length. The parameters calculated on the surface repeat the parameter calculation methods used on the profiles, taking the same name preceded by the letter uS", for instance, the Wa parameter becomes sWa, with the same definition. Figure 3. Surface parameters determined in this study. skin thickness (21). Elasticity measurements were carried out five times at the same area, and values were averaged to obtain Uf and Ur/Uf values. Measurement of skin conductance. Changes in the water content of the cheek skin were measured using a skin surface hygrometer (Skicon-200, IBS Co., Hamamatsu, Japan). Conductance measurements were carried out five times at the same area, and values were averaged to obtain individual values. Statistical analysis. The correlation coefficient was calculated from an exponential regres- sion curve using all data. Differences were analyzed by Student's t-test. RESULTS BLOOD FLOW PARAMETERS AND AGE Table I shows the relationship between the blood flow parameters and the age of cheek and forehead skin. No significant correlations were obtained for the cheek skin of elderly subjects aged 60 years or above. However, for the forehead skin, the values of parameters Fn, ax (p 0.05) showed age-associated decreases. CORRELATION BETWEEN AGE AND SURFACE PARAMETERS AT DIFFERENT AREAS OF THE FACE Table II shows the correlation coefficients between age and surface parameters at dif- ferent areas of the face, calculated from the linear and exponential regression curves. Age-associated increases were observed in sWa (p 0.01), sWp (p 0.005), and sWt (p

504 JOURNAL OF COSMETIC SCIENCE Table I Correlation Coefficients Between Age (above 60 years) and Blood Flow Parameters in the Cheek and Forehead Correlation coefficient Linear Exponential Parameters No. in group Cheek Forehead F .... 40 Fmt•r_ L 40 Fmi n 40 Fx•x 40 Fpost_L 40 -0.077 -0.200 -0.094 -0.228 -0.197 -0.296 -0.184 -0.114 -O.246 -0.230 -0.118 -0.272 -0.100 -0.306' -0.158 -0.256 -0.130 -0.300 *p 0.05. Table II Correlation Coefficients Between Age (above 60 years) and Surface Parameters at Several Sites of Facial Skin Parameters Correlation coefficient Linear Exponential No. in Corner Lower Nasolabial Corner of group of eye eyelid groove mouth Cheek Forehead 0.221 0.031 0.268 0.148 0.404** 0.181 sWa 40 0.151 0.000 0.301 0.094 0.313' 0.192 0.439*** 0.083 0.407** 0.228 0.433*** 0.126 sWp 40 0.342* 0.063 0.402** 0.148 0.376* 0.122 0.225 0.044 0.242 0.077 0.424** 0.154 sWt 40 0.137 0.000 0.272 0.054 0.340* 0.151 0.236 0.000 0.260 0.148 0.114 0.176 sWq 40 0.154 0.000 0.300 0.094 0.134 0.181 *p 0.05 **p 0.001 ***p 0.005. 0.01) on the cheek, in sWp (p 0.005) at the outer corner of the eye, and in sWp (p 0.01) on the nasolabial groove. RELATIONSHIP BETWEEN BLOOD FLOW AND SURFACE MORPHOLOGY OF THE FOREHEAD Table III shows the correlations between the blood flow parameters and surface morphol- ogy parameters of the forehead. No correlation was observed in any combination of the parameters, either by logarithmic regression or by linear regression.