Pre-admission use of platelet inhibitors and short-term stroke mortality: a population-based cohort study

Aims: The impact of pre-admission antiplatelet treatment on prognosis after stroke is poorly understood. We, therefore, investigated whether pre-admission use of aspirin and clopidogrel was associated with mortality in patients hospitalized with ischaemic stroke, intracerebral haemorrhage (ICH), or subarachnoid haemorrhage (SAH). Methods and results: We used nationwide population-based registries to identify all first-time hospitalizations for stroke and subsequent mortality in patients treated with aspirin and clopidogrel in Denmark during 2004-2012. Based on redeemed prescriptions, we computed absolute 30-day mortality rates and mortality rate ratios (MRRs) for current platelet inhibitor users and non-users. We used Cox regression to control for potentially confounding factors. Among platelet inhibitor non-users, 30-day stroke mortality was 12.0% (8.8% for ischaemic stroke, 29.6% for ICH, and 21.2% for SAH). Compared with non-users, the adjusted 30-day MRR (aMRR) was increased among ICH patients using aspirin [1.19, 95% confidence interval (CI) 1.09-1.31]. Although wider CIs, similar increased point estimates were observed in users of both aspirin and clopidogrel (aMRR = 1.26, 95% CI 0.84-1.91). In contrast, current use of both aspirin and clopidogrel was associated with reduced mortality from ischaemic stroke (aMRR = 0.67, 95% CI 0.48-0.94), while use of aspirin alone was not. Conclusion: Among patients hospitalized for first-time ICH, pre-admission platelet inhibitor use was associated with increased 30-day mortality compared with non-use. In patients hospitalized for ischaemic stroke, 30-day mortality was reduced in users of both aspirin and clopidogrel, but not in users of aspirin alone.