Age-related differences in tissue dielectric constant values of female forearm skin measured noninvasively at 300 MHz.

BACKGROUND/PURPOSE We hypothesized that reported age-related shifts in skin water from less-to-more mobile states would result in increased skin tissue dielectric constant (TDC) values as TDC values depend strongly on water content and state. One aim was to test this hypothesis. Further, as skin-to-fat TDC values are used as a tool for edema and lymphedema assessment, a second aim was to establish reference values suitable for young and older women. METHODS TDC was measured bilaterally on volar forearm skin in young (20-40 years) and older (≥60 years) women. There were four groups with 50, 50, 100, and 50 subjects per age group measured to depths of 0.5, 1.5, 2.5, and 5.0 mm, respectively. RESULTS For each age group, TDC values decreased with increasing depth (P < 0.001). TDC values at 0.5 and 1.5 mm were greater for older women (P < 0.001). At 2.5 mm, there was no age-group difference (P = 0.108). At 5.0 mm the direction of the difference reversed with older TDC values less than the younger (P < 0.001). CONCLUSION Results are consistent with age-related shifts in water state from less-to-more mobile and explain depth-dependence differences between age groups. Data also give age-related TDC reference values for assessing local edematous or lymphedematous states.