Serum Levels of CRP are Associated with Depression in a Middle-aged and Elderly Population with Diabetes Mellitus: A Diabetes Mellitus-Stratified Analysis in a Population-Based Study

The direct relationship between inflammation and depression in patients with diabetes is still unclear. We examined the association between serum C-reactive protein (CRP) levels and the high prevalence of depression in populations (aged ≥49 years) with and without type 2 diabetes.Cross-sectional and longitudinal data from 3895 participants obtained from The Irish Longitudinal Study on Ageing (TILDA) were analyzed to determine the association between serum CRP levels and depression, accounting for relevant confounding factors.Multivariable analyses showed a positive association between serum CRP and depression score, independent of age and gender, BMI, marital status, education, smoking status, alcohol drinking status, systolic BP, diastolic BP, physical activity, self-reported CVDs and laboratory measurements in subjects with diabetes mellitus (coefficient = 0.179, P<0.001) but not in subjects without diabetes mellitus (coefficient = 0.011, P = 0.495). Higher serum CRP levels were associated with an increased risk of depressive symptoms in subjects with diabetes mellitus (OR = 1.301, 95% CI 1.012-1.799, P = 0.011) but not in subjects without diabetes mellitus (OR = 1.004, 95% CI 0.992-1.013, P = 0.344) after adjusting for these same confounding factors. After a follow-up of 4 years, higher serum CRP levels were significantly associated with a higher possibility of depression events in subjects with diabetes mellitus.Time-varying confounding factors may interfere with our results.We observed a significant positive association between serum CRP levels and the prevalence of depressive symptoms in a middle-aged and elderly population with diabetes after adjustment for a range of lifestyle factors.