Objective: The aim of the study was to evaluate associations between 15-year trajectories of co-occurring depressive symptoms and smoking with biomarkers of cardiovascular disease at year 15.
Methods: In the Coronary Artery Risk Development in Young Adults study, we modeled trajectories of depressive symptoms (Center for Epidemiologic Studies-Depression scale [CES-D]) and smoking (cigarettes per day [CPD]) among 3614 adults followed from year 0 (ages 18-30 years) through year 15 (ages 33-45 years). Biomarkers of inflammation (high-sensitivity C-reactive protein), oxidative stress (superoxide dismutase, F2-isoprostanes), and endothelial dysfunction (soluble intercellular adhesion molecule 1, soluble P-selectin) were assessed at year 15. We conducted separate linear regression analyses with CES-D trajectory, CPD trajectory, and their interaction with each of the five biomarkers.
Results: The sample was 56% women, 47% black, and 40 years old on average at year 15. The CES-D trajectory by CPD trajectory interaction was not associated with any of the biomarkers (all p's > .01). Removing the interaction term, CES-D trajectory was associated with inflammation: higher levels of high-sensitivity C-reactive protein were observed in the subthreshold (β = 0.57, p = .004) and increasing depressive symptoms (β = 1.36, p < .001) trajectories compared with the no depression trajectory. CPD trajectory was associated with oxidative stress and endothelial dysfunction: compared with never smokers, heavy smokers had significantly higher levels of F2-isoprostanes (β = 6.20, p = .001), soluble intercellular adhesion molecule 1 (β = 24.98, p < .001), and soluble P-selectin (β = 2.91, p < .001).
Conclusions: Co-occurring depressive symptoms and smoking do not seem to synergistically convey risk for cardiovascular disease via processes of inflammation, oxidative stress, or endothelial dysfunction. Nonetheless, these results advance our understanding of the complex relationships between modifiable risk factors and chronic disease.