Association between the ratio of serum arachidonic acid to eicosapentaenoic acid and the presence of depressive symptoms in a general Japanese population: the Hisayama Study

Background: Epidemiological evidence suggests that fish consumption and intake of n-3 polyunsaturated fatty acids (PUFA)—namely, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)—confer protection against depression. However, few studies have addressed the influence of the balance between n-3 PUFA and n-6 PUFA in the human body on depression. Methods: A total of 2,529 community-dwelling Japanese residents aged ≥ 40 years were assessed for depressive symptoms (defined as a score of 16 points or more on the Center for Epidemiologic Studies Depression Scale [CES-D]) in 2007. The serum arachidonic acid (AA) /EPA ratio and AA/DHA ratio were measured in frozen samples collected in 2002 and categorized into quartiles. The odds ratios (ORs) for the presence of depressive symptoms were calculated using a logistic regression model. Results: The prevalence of depressive symptoms was 4.3%. There was no significant association between either the serum AA/EPA ratio or AA/DHA ratio and the presence of depressive symptoms. However, subjects with the highest serum AA/EPA ratios (range: 3.28–13.3) had a 4.10 times (95%CI: 1.13–19.80) greater OR for the presence of depressive symptoms than those with the lowest ratios (0.30–1.65) after adjusting for confounding factors in the subgroup with high-sensitivity C-reactive protein (hs-CRP) ≥ 1.0 mg/L, while no clear association was observed in the subgroup with hs-CRP < 1.0 mg/L. Limitations: Reverse causality is possible due to the cross-sectional study design. Conclusions: Our findings suggest that a higher serum AA/EPA ratio is associated with a greater likelihood of depressive symptoms in subjects with systemic inflammation in the general Japanese population.