During the 1980s, serum total cholesterol (TC) levels in Japanese adults increased due to lifestyle changes. These levels were thought to plateau after 1990. We investigated national trends in the TC levels during the past decade using Lorenz plot which shows a relation between the mean TC levels during year t, and that of the following year, t+1. The trace of the plotted values revolved clockwise with a cycle of four to five years, and the approximate center of the circle was on the line x=y. For TC levels in men and in women in their 50s, the initial traces each primarily revolved around a single locus. However, during the latter part of the 1990s, the traces associated with the TC levels shifted to form additional circles. The difference between the centers of these circles was 7mg/dl. Our method of documenting changes in the mean TC levels in Japanese adults provides information about a non-linear trend occurring in the population.

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