The relationship between the dietary inflammatory index (DII®) and incident depressive symptoms : a longitudinal cohort study

BACKGROUND: Diet is a common source of inflammation, and inflammation is associated with depression. We examined the association between the dietary inflammatory index (DII®), a validated measure of inflammatory potential of the diet, and risk of depression in a cohort of older North American adults. METHODS: This longitudinal study, with a follow-up of 8 years, included 3,648 participants (1,577 males, 2,071 females; mean age: 60.6 years) with/at risk of knee osteoarthritis. DII® scores were calculated using the validated Block Brief 2000 Food-Frequency Questionnaire. Center for Epidemiological Studies Depression-20 scale was used to define depressive symptoms. The relationship between baseline DII® score and incident depression was assessed through Cox's regression analysis, adjusted for potential confounders, and reported as hazard ratios (HRs). RESULTS: In total, 837 individuals (310 men and 527 women) developed incident depressive symptoms over the course of 8 years. Participants in the most pro-inflammatory group (quartile 4) had approximately 24% higher risk of developing depressive symptoms compared to subjects with the most anti-inflammatory diet (HR: 1.24; 95% CI: 1.01-1.53; p=0.04). CONCLUSION: These results suggest that a pro-inflammatory diet may be associated with higher incidence of depressive symptoms in a cohort of older Americans. Transitioning to a more anti-inflammatory diet may reduce depression risk.