Warfarin and elderly patients: a challenging combination

Atrial fibrillation (AF) incidence increases according to patient age.
Oral anticoagulant therapy with vitamin K antagonists, like warfarin, reduces stroke risk in AF patients, including elderly.[1,2] The INR (International Normalized Ratio) normal range for atrial fibrillation lays between 2 and 3.[3] Increased risk for thromboembolism[4] is associated with INR<2 and increased risk for major haemorrhages with INR>4.[5] Unfortunately, to keep INR values between 2 and 3 is challenging in daily clinic practice.
Elderly patients are often undertreated with vitamin K antagonists mostly because the risk for haemorrhages is age-correlated.[2] Practitioners are reluctant to prescribe warfarin for AF elderly patients, despite the major benefit evidences for these patients compared to the younger ones.[6,7] According to a recent study, however, about 33% of elderly patient hospitalizations due to ADRs (Adverse Drug Reactions) - mostly haemorrhagic – are caused by warfarin, and another 13% by anti-platelet drugs, with high risk for patients and costs for society.8 A correct evaluation of risk factors is then essential. Positive anamnesis for bleeding or falls and active phase cancer are independent risk factors for bleeding in patients treated with vitamin K antagonist.[9]
Cognitive impairment, a frequent condition in AF elderly patients, is associated with suboptimal vitamin K antagonist therapy and consequently with increased risk for bleeding or vascular events.[10]
Polytherapy in elderly patients and warfarin interactions with other drugs and foods[11] - which practitioners should be well aware of in order to avoid or at least monitor them more cautiously- are also source of possible complications.
Several stroke risk factors can predict haemorrhagic risk as well, but stroke risk usually overcomes major haemorrhagic one; besides more than 70% of strokes with atrial fibrillation are fatal or leave residual deficits (disabilities), while major haemorrhages are less often fatal or permanently disabling.[12]
Randomized controlled trials of vitamin K antagonists in AF patients have showed a significant reduction in ischemic cardiovascular events and stroke – with only a slight increase in severe bleeding – and a clear benefit over acetylsalicylic acid for elderly patients. In contrast, anticoagulant therapy benefits appear to decrease when age increases and are not evident anymore in patients older than age 77 years.[13]
To conclude, age9 and fall risk in older population13 should not prevent to initiate warfarin therapy.