The relationship between the joint effect of C-reactive protein and glycated hemoglobin with the risk of depressive symptoms among middle-aged and older adults: Findings from the China health and retirement longitudinal study

Objectives: The present study aimed to explore the relationship between the joint effect of C-reactive protein and glycated hemoglobin with the risk of depressive symptoms among middle-aged and older adults.Methods: A total of 5985 participants aged 45 years or older from the China Health and Retirement longitudinal study 2011 and 2015 were included in this study. Participants were divided into 4 groups according to C-reactive protein and glycated hemoglobin. Multivariate logistic regression model was used to explore the associations between C-reactive protein and glycated hemoglobin and new-onset depression.Results: During the follow-up period, 1001(16.73%) participants experienced depressive symptoms. Compared to participants with low C-reactive protein and low glycated hemoglobin, individuals with C-reactive protein and glycated hemoglobin both high levels have a higher risk to suffer from depressive symptoms with corresponding multivariable adjusted odds ratio (OR = 1.17, 95% CI: 1.01-1.36). Adding C-reactive protein and glycated he-moglobin simultaneously to conventional risk model significantly improved risk reclassification for depressive symptoms. The statistically significant interaction with joint effects of C-reactive protein and glycated hemo-globin on depressive symptoms was only found in different sex (P-interaction = 0.006) or age (P-interaction = 0.004) groups. Sensitivity analysis yields similar results.Conclusions: Higher levels of C-reactive protein and glycated hemoglobin jointly increased the risk of depressive symptoms among Chinese middle-aged and older adults. Using the combination indicator of C-reactive protein and glycated hemoglobin could better identify individuals at risk of depressive symptoms.