The relationship of hair zinc concentrations to height, weight, age, and sex in the normal population.

Hair samples from forty-nine normal individuals (both children and adults) were assessed for concentrations of zinc. Pearson correlation coefficients were computed between zinc values and the variables: height, weight, and age (see Table 3). In children (under 240 months), all these relationships were linear, positive, and statistically significant. A linear regression equation using all these variables was found to account for 47.7% of the variance in hair zinc concentrations. In adults (over 240 months), the correlation coefficients between hair zinc and height, weight, and age were not found to be significant, with the exception of the negative correlation between hair zinc and weight (r = -0.464; P less than 0.047). Nevertheless, a multivariate linear regression equation accounted for about 24.6% of the variability of hair zinc values. In both children and adults, tests for sex differences in means and standard deviations using both raw score and residual values failed to reveal any significant differences. Similarly, no significant sex differences were observed between corresponding correlation coefficients. Results indicate that future studies utilizing hair must systematically or mathematically control for individual variation in zinc concentrations due to differences in age, weight, and height.