Epigenetic clocks are widely used aging biomarkers calculated from DNA methylation data. Unfortunately, measurements for individual CpGs can be surprisingly unreliable due to technical noise, and this may limit the utility of epigenetic clocks. We report that noise produces deviations up to 3 to 9 years between technical replicates for six major epigenetic clocks. The elimination of low-reliability CpGs does not ameliorate this issue.Here, we present a novel computational multi-step solution to address this noise, involving performing principal component analysis on the CpG-level data followed by biological age prediction using principal components as input. This method extracts shared systematic variation in DNAm while minimizing random noise from individual CpGs. Our novel principal-component versions of six clocks show agreement between most technical replicates within 0 to 1.5 years, equivalent or improved prediction of outcomes, and more stable trajectories in longitudinal studies and cell culture. This method entails only one additional step compared to traditional clocks, does not require prior knowledge of CpG reliabilities, and can improve the reliability of any existing or future epigenetic biomarker. The high reliability of principal component-based epigenetic clocks will make them particularly useful for applications in personalized medicine and clinical trials evaluating novel aging interventions..
Epigenetic clocks are widely used aging biomarkers calculated from DNA methylation data. Unfortunately, measurements for individual CpGs can be surprisingly unreliable due to technical noise, and this may limit the utility of epigenetic clocks. We report that noise produces deviations up to 3 to 9 years between technical replicates for six major epigenetic clocks. The elimination of low-reliability CpGs does not ameliorate this issue. Here, we present a novel computational multi-step solution to address this noise, involving performing principal component analysis on the CpG-level data followed by biological age prediction using principal components as input. This method extracts shared systematic variation in DNAm while minimizing random noise from individual CpGs. Our novel principal-component versions of six clocks show agreement between most technical replicates within 0 to 1.5 years, equivalent or improved prediction of outcomes, and more stable trajectories in longitudinal studies and cell culture. This method entails only one additional step compared to traditional clocks, does not require prior knowledge of CpG reliabilities, and can improve the reliability of any existing or future epigenetic biomarker. The high reliability of principal component-based epigenetic clocks will make them particularly useful for applications in personalized medicine and clinical trials evaluating novel aging interventions.
ObjectiveNo consensus exists on whether clozapine should be prescribed in early stages of psychosis. This systematic review and meta‐analysis therefore focus on the use of clozapine as first‐line or second‐line treatment in non‐treatment‐resistant patients.MethodsArticles were eligible if they investigated clozapine compared to another antipsychotic as a first‐ or second‐line treatment in non‐treatment‐resistant schizophrenia spectrum disorders (SCZ) patients and provided data on treatment response. We performed random‐effects meta‐analyses.ResultsFifteen articles were eligible for the systematic review (N = 314 subjects on clozapine and N = 800 on other antipsychotics). Our meta‐analysis comparing clozapine to a miscellaneous group of antipsychotics revealed a significant benefit of clozapine (Hedges’ g = 0.220, P = 0.026, 95% CI = 0.026–0.414), with no evidence of heterogeneity. In addition, a sensitivity analysis revealed a significant benefit of clozapine over risperidone (Hedges’ g = 0.274, P = 0.030, 95% CI = 0.027–0.521).ConclusionThe few eligible trials on this topic suggest that clozapine may be more effective than other antipsychotics when used as first‐ or second‐line treatment. Only large clinical trials may comprehensively probe disease stage‐dependent superiority of clozapine and investigate overall tolerability.
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