The study looked at changes in blood levels of certain fatty acids in Japanese adults over 13 years. They found that arachidonic acid levels increased in all age groups, while eicosapentaenoic and docosahexaenoic acid levels increased in younger and middle-aged adults. Arachidonic acid composition also increased over 4 years in middle-aged adults, even after considering dietary intake. This suggests a trend of rising arachidonic acid levels in middle-aged and elderly Japanese adults living in the community.