Objectives: Raised levels of C-reactive protein (CRP), an inflammatory biomarker, and depressive symptoms are both independently linked to risk of diabetes. The purpose of this study was to assess the joint association of CRP and depressive symptomatology with diabetes incidence in a representative sample of English people ≥50 years old.
Method: Data were from the English Longitudinal Study of Ageing, a prospective study of community-dwelling older adults. The sample was comprised of 4955 participants without self-reported doctor-diagnosed diabetes at baseline. High CRP level was dichotomized as >3 mg/L. Elevated depressive symptomatology was defined as ≥4 using the 8-item Center for Epidemiologic Studies Depression Scale. Incident diabetes was determined based on newly self-reported doctor-diagnosed diabetes. Cox proportional hazard regressions were used to examine the association between CRP and depressive symptoms with incidence of type 2 diabetes.
Results: During approximately 63.2 months of follow-up, 194 participants reported diabetes diagnosis. After adjustment for socio-demographics, lifestyle behaviors, clinical factors, and BMI, the hazard ratio for diabetes was 1.63 (95% CI 0.88-3.01) for people with elevated depressive symptoms only, 1.43 (95% CI 0.99-2.07) for people with high CRP only, and 2.03 (95% CI 1.14-3.61) for people with both high CRP and elevated depressive symptoms.
Conclusion: The presence of both high CRP levels and elevated depressive symptoms was associated with risk of diabetes. Further investigation into this relationship could aid in understanding the mechanisms underlying inflammation, depression, and diabetes.
Keywords: C-reactive protein; Depression; Diabetes; Longitudinal; Older adults.
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