Low Serum Tryptophan Levels as an Indicator of Global Cognitive Performance in Nondemented Women over 50 Years of Age

Figure 1

The lower triangular matrix contains the scatterplot for each pair of variables in the logarithmic scale. The upper triangular matrix contains Spearman’s rank correlation coefficient and its associated value. In this case, the variable cognition corresponds to an ordinal variable with four categories depending on the level of cognitive impairment: normal, mild, moderate, and severe.