U-shaped association between systemic immune-inflammatory index and depression in U.S. adults with hypertension

Depression frequently occurs alongside hypertension and is linked to inflammation. Treating inflammation might alleviate depression. It is unclear how the systemic immune-inflammatory index (SII) and depression relate to each other in hypertensive participants.

Through multivariate logistic regression and smoothed curve fitting, the relationship between SII and depression in hypertensive individuals was examined employing data from the 2005 and 2020 NHANES. The accuracy of the relationships between various demographic features was investigated using subgroup analyses and interaction tests.

The study, which contained 19,096 individuals aged 20 to 85, identified a positive correlation between SII and depression. In the fully adjusted model, each unit increase in log SII was associated with a 14 % increase in the prevalence of depression [OR = 1.14, 95 % CI (1.04, 1.25)]. SII quartile 4 was significantly positively correlated with depression. The greatest SII quartile had a 19 % higher prevalence of depression than the lowest SII quartile [OR = 1.19, 95 % CI (1.04, 1.37)]. Subgroup analyses suggested that the correlation between SII and depression did not change across subgroups of hypertensive individuals. A U-shaped association between SII and depression in hypertension was found using smooth curve fitting, with the threshold effect's inflection point being 6.16. After the inflection point, SII and depression were positively associated in hypertension [OR = 1.55, 95 % CI (1.34, 1.80)].

This cross-sectional study is unable to establish a causal relationship.

With a threshold effect of 6.16, SII showed a U-shaped correlation with depression in hypertension in the US.