Depression as a Driving Force for Low Time in Therapeutic Range and Dementia in Patients With and Without Atrial Fibrillation.

Both time in therapeutic range (TTR) for anticoagulation and depression are associated with dementia risk. The purposes of this study were to examine the impact of depression on TTR and to describe the partitioned contribution of depression and TTR on long-term dementia risk. We studied 14,953 patients anticoagulated with warfarin (target INR 2-3) for atrial fibrillation (AF), venous thromboembolism (VTE), or a mechanical heart valve from 2003 to 2015. We excluded patients with a diagnosis of dementia before or within 6 months of warfarin initiation. We examined the association of depression with TTR using finite mixture modeling and logistic regression and utilized multivariable Cox hazard regression to determine the association of TTR and depression with incident dementia at 3 and 13 years. Forty % (n = 6055) of patients were diagnosed with depression before or while on warfarin. Patients with depression had significantly lower TTR and were 1.37 times more likely to have TTR <50% than non-depressed patients (p <0.0001). During follow-up, 4.2% of patients received the diagnosis of dementia within 3 years as compared to 12% during all-time follow up. The 3-year risk of dementia was highest for patients with a ≤50% TTR regardless of depression status. The 3-year dementia risk was associated with TTR (p <0.0001) but not depression. However, for all-time dementia both TTR (p <0.0001) and depression (p <0.0001) as well as their interaction (p = 0.049) were associated with dementia. Depression increased the risk of long-term dementia by 1.69 fold (95% CI: 1.33, 2.15) for patients with the lowest TTR. Depression is prevalent in patients managed with warfarin and is associated with significant decreases in TTR. In conclusion, decreased TTR appears to increase 3-year dementia risk and both low TTR and depression interact to increase risk for all-time dementia in patients taking warfarin.