Many of the common cardiovascular disorders (especially in elderly people) are linked to thrombosis—such as ischaemic heart disease, atrial fibrillation, valve disease, hypertension, and atherosclerotic vascular disease—requiring the use of antithrombotic therapy. This raises questions regarding the appropriate use of antithrombotic therapy in older people, especially because strategies such as anticoagulation with warfarin need regular monitoring of the international normalised ratio (INR), a measure of the induced haemorrhagic tendency, and carry a risk of bleeding. The presence of concomitant physical and medical problems increases the interactions and risks associated with warfarin, and anticoagulation in elderly patients often needs an assessment of the overall risk:benefit ratio.

ISI=international sensitivity ratio. The mean normal prothrombin time is often generated from samples from local healthy subjects or a commercially available standard. The exact value of the ISI depends on the thromboplastin used in the prothrombin time method

Physical frailty in elderly people may reduce access to anticoagulant clinics for INR monitoring. The decline in cognitive function in some elderly patients also may reduce compliance with anticoagulation and the appreciation of bleeding risks and drug interactions. However, in recent studies of anticoagulation in elderly people, no significant associations of anticoagulant control were found with age, sex, social circumstances, mobility, domicillary supervision of medication, or indications for anticoagulation.