Effectiveness and safety of intracranial events associated with the use of direct oral anticoagulants for atrial fibrillation: A systematic review and meta-analysis of 92 studies.

AIMS: Observational studies have investigated the effectiveness and safety of direct oral anticoagulants (DOACs) and vitamin K antagonists (VKAs) used in nonvalvular atrial fibrillation. We performed a systematic review and meta-analysis assessing the risk of ischaemic stroke, thromboembolism (TE) and intracranial haemorrhage (ICH) associated with the use of DOACs and VKAs. METHODS: Medline and Embase were systematically searched until April 2021. Observational studies were gathered and hazard ratios (HRs) with 95% confidence intervals (CI) were extracted. Subgroup analyses based on DOAC doses, history of chronic kidney disease, stroke, exposure to VKA, age and sex were performed. A random-effects model was used. RESULTS: We included 92 studies and performed 107 comparisons. Apixaban was associated with lower risk of stroke (HR: 0.82, 95% CI: 0.68-0.99) compared to dabigatran. Rivaroxaban was associated with lower risk of stroke (HR: 0.90, 95% CI: 0.83-0.98) compared to VKA. Dabigatran (HR: 0.85, 95% CI: 0.80-0.91), rivaroxaban (HR: 0.83, 95% CI: 0.77-0.89) and apixaban (HR: 0.75, 95% CI: 0.65-0.86) were associated with lower risk for TE/stroke compared to VKA. Apixaban (HR: 1.32, 95% CI: 1.03-1.68) and rivaroxaban (HR: 1.58, 95% CI: 1.31-1.89) were associated with higher risk of ICH compared to dabigatran. Dabigatran (HR: 0.48, 95% CI: 0.44-0.52), apixaban (HR: 0.60, 95% CI: 0.49-0.73) and rivaroxaban (HR: 0.73, 95% CI: 0.65-0.81) were associated with lower risk of ICH compared to VKA. CONCLUSION: Our study demonstrated significant differences in the risk of ischaemic stroke, TE/stroke and ICH associated with individual DOACs compared to both other DOACs and VKA.

Berkson's paradox and weighted distributions: An application to Alzheimer's disease.

One reason for observing in practice a false positive or negative correlation between two random variables, which are either not correlated or correlated with a different direction, is the overrepresentation in the sample of individuals satisfying specific properties. In 1946, Berkson first illustrated the presence of a false correlation due to this last reason, which is known as Berkson's paradox and is one of the most famous paradox in probability and statistics. In this paper, the concept of weighted distributions is utilized to describe Berskon's paradox. Moreover, a proper procedure is suggested to make inference for the population given a biased sample which possesses all the characteristics of Berkson's paradox. A real data application for patients with dementia due to Alzheimer's disease demonstrates that the proposed method reveals characteristics of the population that are masked by the sampling procedure.