Évaluation comparative de stratégies visant à augmenter les interventions de courte durée en cessation tabagique auprès du personnel infirmier de milieux hospitaliers

Introduction : Les résultats de recherches ont démontré que la cessation tabagique augmente là où des interventions professionnelles préventives sont appliquées avec constance. On rapporte qu’au Québec, 62 % des infirmières (toutes pratiques confondues) évaluent le statut tabagique de leurs clients et 38 % suggèrent la cessation tabagique. En milieu hospitalier, l’évaluation du statut tabagique diminue à 30 %. Or, le personnel infirmier hospitalier est présent dans les unités de soins 24 heures sur 24, ce qui laisse prévoir une influence potentielle non négligeable dans la décision des patients de cesser de fumer. Objectif : La présente recherche a pour objectif de comparer, avec un groupe contrôle, l’efficacité de stratégies (formation interactive, rappel, multiple) pour augmenter les interventions réalisées en cessation tabagique dans des unités de médecine et de chirurgie. Le choix de ces stratégies repose sur leur efficacité et leur potentiel d’implantation dans d’autres centres. Méthodologie : Un devis expérimental avec randomisation par groupe a été choisi. Le modèle factoriel permet d’évaluer l’effet de chacun des groupes expérimentaux en regard du groupe contrôle. Des mesures préstratégies et poststratégies (à 1 mois et à 3 mois) sont privilégiées. Plusieurs outils permettent de mesurer les effets des stratégies et ce, avec des sources diversifiées (personnel infirmier, patients, dossiers des patients, gestionnaires et responsables des centres d’abandon du tabac). Résultats : Au total, 156 infirmières et infirmières-auxiliaires ont répondu à des questionnaires au temps 1, 78 au temps 2 et 69 au temps 3. Parallèlement au personnel infirmier, 156 patients ont été rejoints au temps 1, 89 au temps 2 et 98 au temps 3. Les résultats démontrent que le personnel infirmier évalue le statut tabagique chez 35,7 % de la clientèle seulement et la motivation à cesser de fumer chez 17,6 % des patients. Au cours de notre recherche, peu d’interventions en cessation tabagique ont été réalisées dans les unités de médecine et de chirurgie; la présence de plusieurs obstacles de même qu’une perception d’inefficacité des interventions de la part du personnel infirmier semblent en être les causes. Les résultats de notre recherche ne nous a pas permis d’appuyer nos hypothèses. Cependant, des analyses complémentaires ont démontré que la stratégie de formation interactive a permis d’augmenter certaines pratiques cliniques à court terme et de diminuer la perception d’obstacles à l’intervention. Le rappel n’a pas fonctionné correctement et n’a pu être évalué. Conclusion : En considérant les résultats modestes des stratégies implantées, la formation interactive a eu un impact à très court terme sur les interventions courtes en cessation tabagique réalisées par le personnel infirmier d’unités de soins en médecine et en chirurgie. Les difficultés rencontrées lors de l’implantation des stratégies ont été expliquées, ce qui permettra une planification plus éclairée de futures recherches dans le domaine.Introduction : Research results demonstrate a decrease in cigarette smoking when preventive professional interventions are routinely carried out. The Quebec recent literature reports that, nurses from different working areas assess their patient smoking habits 62 % of the time and recommend cessation in only 38 % of the situations. When this assessment is realized by hospital nurses, this percentage drops around 30 %. Knowing that nursing staff is present at the bedside 24 hours a day, a non-negligible influence of tobacco counselling by nurses is of potential interest for hospitalized patients. The objective of the present study is to compare, on medical and surgical units, the effectiveness of three strategies (interactive educational session, recall, and both together) to a control group, on the number of nursing interventions pertaining to cessation of cigarette smoking. Choice of those three strategies is based on reported effectiveness and transferability potential. Research design is experimental with group randomisation. Factorial model opens possibility to assess impact of each of the three strategies versus the control group. Pre and post strategy multi-measurements (at 1 and 3 months) are sought from nursing staff, patients, patient charts, management, nurses in charge of the centers for tobacco cessation. Results : Nursing staff completed questionnaires at time 1 (N = 156), at time 2 (N= 78), and at time 3 (N=69). Similarly, 156 patients were interviewed at time 1, 89 at time 2, and 98 at time 3. Results show that nursing staff assesses cigarette smoking habits for only 35,7 % of the patients, and their intent to stop smoking only 17,6 % of the time. Very few tobacco counselling interventions are carried out on medical and surgical units by nursing staff. Some barriers are identified, and nursing staff perceives a non-self-efficacy with regard to those interventions. Results do not allow confirmation of hypotheses. However, complementary statistical analyses show that the educational strategy increases the number of nursing interventions during a short period, and decreases perception of barriers to tobacco counselling. Impact of recall could not be assessed as it was not introduced as planned. Conclusion : Considering modest results from the strategies, the interactive educational sessions shows a short term effect on the nursing staff’s interventions,. The difficulties encountered during implementation of the strategies have been explained, which will be useful when planning future research in tobacco cessation

La démarche de développement d’indicateurs basés sur l’ichtyofaune pour évaluer la qualité écologique des eaux de transition françaises dans le cadre de la DCE : une marche forcée pour des résultats positifs

Cet article se propose d’expliquer, sur l’exemple de l’ichtyofaune des masses d’eau de transition, la démarche adoptée par la France pour répondre aux objectifs de la DCE et les défis qu’elle présentait dans des délais contraints. Nous présentons le vide de connaissances et de données qui régnait au début des années 2000 et les actions mises en œuvre au pas de charge pour répondre aux objectifs ambitieux de la DCE, disposer d’un réseau de surveillance en 2007, puis d’indicateurs normés décrivant l’état écologique afin de présenter un bilan six ans plus tard, en 2013, à l’issue du premier plan de gestion. Il reste désormais à poursuivre la démarche en milieu marin dans le cadre de la DCSMM.In this paper, we propose to study fish in transition waters to illustrate the challenge of meeting the goals of the European Union Water Framework Directive (EWFD) in France in restricted delays. We present the lack of knowledge and data in early 2000s and the actions led then to achieve the ambitious objectives of the EWFD: the creation of a standardized monitoring network in 2007 and the definition of ecological indicators based on the fish community. In 2013, at the end of the first management plan, an assessment of the ecological status was presented. These actions have now to be continued towards marine waters in relation with the EU Marine Strategy Framework Directive

Fish under influence: a macroecological analysis of relations between fish species richness and environmental gradients among European tidal estuaries

Estuarine fish assemblages are subject to a great environmental variability that largely depends on both upstream fluvial and downstream marine influences. From this ecohydrological view, our study introduces a macroecological approach aiming to identify the main environmental factors that structure fish assemblages among European tidal estuaries. The present paper focuses on the influence of large scale environmental gradients on estuarine fish species richness. The environment of 135 North-eastern Atlantic estuaries from Portugal to Scotland was characterized by various descriptors especially related to hydromorphology. Major environmental trends among estuaries were underlined using multivariate techniques and cluster analyses applied to abiotic data. In particular, an integrative system size covariate was derived from a principal component analysis. Factors explaining patterns of species richness at different scales from local habitat to regional features were highlighted. Based on generalised linear models, the estuarine system size, and more particularly the entrance width, and also the continental shelf width were identified as the best explanatory variables of estuarine fish species richness at a large scale. Our approach provides a standardized method to estimate the relationship between fish assemblages and environmental factors. This constitutes a first step in assessing estuarine ecological status and studying the effects of additional factors such as anthropogenic disturbances

A Bayesian framework to objectively combine metrics when developing stressor specific multimetric indicator

In the context of the European Water Framework Directive (WFD), monitoring programs and related indicators have been developed to assess anthropogenic impacts on various components of aquatic ecosystems. While great precautions are usually taken when selecting and calculating relevant core metrics, little attention is generally paid to the generation of the multimetric indicator, i.e. the combination of the different core metrics. Indeed, most multimetric indicators are generated by simply averaging or summing metrics, without taking into account their sensitivity and their variability. Moreover, few indicators provide a rigorous estimate of the uncertainty of the assessments, while this estimation is essential for managers. In this context, we developed a Bayesian framework to build multimetric indicators aiming at improving those two weaknesses. This framework is based on two phases. First, pressure-impact statistical models are developed to quantify the impact of pressure on various fish metrics. Then the Bayesian theorem is applied to estimate probabilities of being at a certain anthropogenic pressure level from fish observation and pressure-impact models outputs. The Bayesian theorem allows to combine objectively the different core metrics, taking into account their sensitivity and their variability, and to provide rigorous uncertainty quantification, which is especially valuable in the WFD context. The method is applied as illustrative example on transitional French water bodies to demonstrate its relevance, especially in the Water Framework Directive context though the method is generic enough to be applied in various contexts

OA Lal 2023 Digital health innovation to prevent relapse and support recovery in young people with first-episode psychosis : A pilot study of Horyzons-Canada

Digital health innovations may help to improve access to psychosocial therapy and peer support; however, the existence of evidence-based digital health interventions for individuals recovering from a first-episode psychosis (FEP) remains limited. This study aims to investigate the feasibility, acceptability, safety, and pre-post outcomes of Horyzons-Canada (HoryzonsCa), a Canadian adaptation of a digital mental health intervention consisting of psychosocial interventions, online social networking, and clinical and peer support moderation. Using a convergent mixed-methods research design, we recruited participants from a specialized early intervention clinic for FEP in Montreal, Canada. Twenty-three participants (mean age = 26.8) completed baseline assessments, and 20 completed follow-up assessments after 8 weeks of intervention access. Most participants provided positive feedback on general experience (85%, 17/20) and the utility of Horyzons for identifying their strengths (70%, 14/20). Almost all perceived the platform as easy to use (95%, 19/20) and felt safe using it (90%, 18/20). There were no adverse events related to the intervention. Participants used HoryzonsCa to learn about their illness and how to get better (65%, 13/20), receive support (60%, 12/20), and access social networking (35%, 7/20) and peer support (30%, 6/20). Regarding adoption, 65% (13/20) logged in at least 4 times over 8 weeks. There was a nonsignificant increase in social functioning and no deterioration on the Clinical Global Impression Scale. Overall, HoryzonsCa was feasible to implement and perceived as safe and acceptable. More research is needed with larger sample sizes and using in-depth qualitative methods to better understand the implementation and impact of HoryzonsCa

Deliverable D4.4-3, Report detailing Multimetric fish-based indices sensitivity to anthropogenic and natural pressures, and to metrics’ variation range

The Water Framework Directive (WFD) aims at achieving good ecological status (GES) for surface water bodies throughout Europe, by 2015. Consequently European countries are currently developing and intercalibrating methods based on biological, hydromorphological and physico-chemical quality elements for the assessment of their transitional waters, including fishes. The present work focuses on the response of fish indicators and indices to anthropogenic pressures and natural factors. For doing that, datasets from the Basque and Portuguese estuaries, in the North East Atlantic, have been used. Hence, biological data from fish (and in some cases, crustaceans), together with different types of pressure (population, industry, ports, dredging, global pressures, pollution, channeling, etc.) and hydromorphological data (flow, estuary volume, depth, intertidal surface, residence time, etc.) have been analyzed. Together with fish assemblages composition and individual metrics (richness, trophic composition, etc.), two fish indices (Basque AFI and Portuguese EFAI) have been investigated. Additionally, the response of five fish indices (AFI, EFAI, ELFI, TFCI, Z-EBI) were tested on a common dataset, within Portuguese estuaries, to check the time lag in the metrics’ response to different human pressures and the variability in the strength of responses to those pressures. This work also focuses on the sensitivity analysis of two European fish-based indices (French ELFI and British TFCI) to changes in their respective metric scores through their observed dynamic range. Sensitivity analyses were run simulating different scenarios of metric score changes, taking into consideration the relationship between metrics. This allowed the metrics with stronger influence in the index score and the resulting water body classification to be highlighted. Importantly, the identification of the most influential metrics could help to guide management efforts in terms of achieving GES by 2015. In general, the fish metrics and indices tested responded to anthropogenic pressures in the Atlantic estuarine sites, yet at the individual metrics level environmental chemical quality was the main driver for observed differences. Also, some metrics did not respond to pressures as expected, which is most likely related to sampling gear efficiency, namely the low capture efficiency of diadromous species with beam trawl. The cause-effect relationship study emphasized that fish-based indices developed to assess the water quality of estuarine systems did not detect all the pressures with the same sensitivity in terms of strength and time-lag, and gave more importance to some pressures, namely chemical pollution. The fish-based indices developed to assess the water quality of estuarine systems do not allow the individualization of pressure effects, which may constitute a problem to put forward the correct specific measures for management and rehabilitation of estuaries. On the other hand, some indices also do not seem relevant, in a short time, to detect changes of the ecological quality which may constitute a handicap for management or an indication for their restructuring. The sensitivity analysis indicates that a number of estuarine resident taxa, a number of estuarine-dependent marine taxa, a number of benthic invertebrate feeding taxa and a number of piscivorous taxa have the greatest influence on the TFCI classification. For the French index ELFI, the most influential metrics are mainly DT (total density) and DB (density of benthic species), followed by RT (total richness). These results suggest a high sensitivity of the quality indication provided by these indices on richness related aspects of the fish assemblages. Management should therefore prioritize efforts to conserve or restore estuarine attributes underpinning abundance and ecological diversity, for example the diversity of fish habitats, food resources and shelter or the hydrological integration between coastal and transitional waters.info:eu-repo/semantics/publishedVersio

Deliverable D4.4-5: Precision and behaviour of fish-based ecological quality metrics in relation to natural and anthropogenic pressure gradients in European estuaries and lagoons

This report summarises the work conducted in Work Package 4.4 – BQE fish in transitional (i.e. estuarine and lagoon) waters (TW) within the project WISER under the sponsorship of the European Commission. It omits most technical details of the analyses given in the four previous Work Package reports, but still provides the necessary information to understand the rationale, approach and underlying assumptions necessary to discuss the results. The focus is therefore to discuss and integrate the results obtained within Work Package 4.4 and with this, make recommendations to improve fish-based ecological assessments in TW, principally estuaries and lagoons. In addition, and to assist with the WFD implementation which is the overarching theme of WISER, the deliverable includes, where appropriate, case studies where we have used multi-metric fish indices currently under development, or already in use for WFD compliance monitoring across Europe. Furthermore, results of the work package have been shared with relevant Geographical Intercalibration Groups (GIGs) supporting the harmonization and equalization process across transitional fish indices in Europe. Development strategies for fish indices in TW vary but generally include: (1) the calibration of metrics to anthropogenic pressures, (2) the development of reference conditions, (3) the calculation of ecological quality ratios, and (4) the designation of thresholds for Ecological Status (ES) class. New fish indices are developed for a defined geographical area, using specific sampling method and under locally relevant pressure fields. The former two factors, area and sampling methods, define the relevant reference condition in the calculation of Ecological Quality Ratios (EQR) and the latter factor, human pressures, define the índex structure and especially the fish metric selection. To assess index relevance across areas, we calculated a suite of transitional fish indices on a standardized WISER dataset and then compared the agreement of the outcomes (using correlation analysis). The application of current indices to areas (or countries) different from the area in which it was originally developed leads to inconclusive or spurious results. The failure to accommodate the diferente indices to a standardized dataset in this work clearly demonstrates the fundamental reliance of current fish indices on the sampling methods and design of monitoring programmes used in the development of the index. Despite this, for some indices, correlations although weaker are statistically significant, also indicating the possible agreement in successful intercalibration between these indices. Harmonization of BQE fish methodologies across Europe (common metrics) is unlikely by adapting or creating new fish indices but inter-comparison assessments are possible and valid using a common pressure index to harmonise diferente indices on a common scale. We found a negative response of fish quality features to pressure gradients which make BQE fish in TW suitable for greater ecological integration than other BQEs. However, successful assessment of Ecological Status (ES) require a matching combination of fish index, reference values and local dataset gathered with compatible sampling methods. Whole indices provide more consistent overall ES assessments but fish metrics considered individually may be more useful as a means to focus restoration measures. Future work is needed to identify those specific pressures affecting fish assemblages providing targets for minimising the effects of stress in mitigation and restoration plans. In order to achieve this, and although the interpretation of outcomes is still difficult, more recent transitional fish indices are leading in the use of comprehensive appraisal and validation exercises to test the responsiveness of BQEs for the assessment of ES. Here we proposed for the first time a simple sensitivity exercise under realistic scenarios of metric change to explore the expected inertia (i.e. the tendency to buffer ES change after quality alterations), dynamic range (i.e. the ratio between the largest and smallest possible ES values) and most relevant metric components (i.e. the those driving the most likely scenarios leading to ES change) from a multi-metric fish índex under relevant human pressure gradients. Overall, the behaviour of multi-metric índices under manipulations of metric scores clearly indicated that metric type, number of metrics used and correlations between metrics are important in determining the index performance, with indices including more and/or uncorrelated metrics or metrics with skewed distribution being less affected by extreme metric manipulations. Results of this analysis may be used to set realistic management targets and also to identify the aspects of the indices that are more likely to affect the outcomes leading to more robust and responsive indices. Further improvements of fish indices may be attained by reducing the variability confounding biological quality metrics. This variability is undesirable noise in assessments and can be technical (i.e. linked to the method of assessment including sampling effort) or natural (physicochemical and biological). The implication for assessments is that different facts might then confound the metric-pressure correlation (the ‘signal’ in the signal-to-noise ratio in the assessments) increasing uncertainty in ES assignment. Models showed that salinity class, depth, season, time of fishing (day vs. night) and year of fishing may influence the values of the fish metrics. The modelling exercise also demonstrated that unexplained variance remains generally much higher within-systems than between-systems suggesting a higher importance of sources of variability acting at the WB level. Modelling and improved standardization in monitoring campaigns should reduce uncertainty in ES assignment. One important factor that was assessed further was the effect of sampling effort. The results suggest that richness-based metrics require larger sampling efforts although a similar effortrelated bias may be an issue for density-based metrics if fish distribution is very patchy (i.e. schooling fish or those aggregated in specific habitats) and insufficient replicates are taken to fully characterise the patchiness in their distribution. It is apparent that to overcome a potential large source of error, the Reference Conditions must be defined according to the level of effort used in the monitoring programme or, conversely, the monitoring must be carried out at the same level of effort used to derive the Reference Condition. The WP finally explored the use of a predictive linear modelling approach to define reference conditions for fish metrics in transitional waters. The fish response data was modelled together with Corine Land Cover (CLC)-derived pressure proxies (% agricultural, urban and natural land coverage). Based on the obtained models, the expected metric score was predicted by setting pressure levels either to the lowest observed pressure in the dataset or to zero in order to define the sample and theoretical reference condition, respectively. Even when significant, the effect of pressures on fish metrics was generally very weak, probably reflecting the use of too-generic pressure indicators (such as land cover data instead of more relevant estuarine proxies such as dredging, port development, waterborne pollutants, etc). The best explanatory models included sampling factors and natural characteristics considered important discriminant features in the definition of water body types. In particular, the present work argues for considering not only estuaries and lagoons as different typologies but also other natural and design characteristic such as the gear type, the sampling season and the salinity class. Furthermore, a relevant reference needs to account for survey design bias, including rare species contribution to assessment datasets, patchiness, choice of pressure proxies or sampling gear. The modelling approach of fish metrics against the physicochemical variables has proved useful to derive Reference Conditions. This is important for the computation of relevant EQRs in Europe where there is a general lack of pristine areas or historical data on fish BQE and it provides an alternative to best professional judgment. Taking all WP analysis and case studies together, the work conducted has highlighted the following key messages and linked research needs necessary to optimize BQE fish for the quality assessment of transitional waters: Key Message 01: Harmonization of BQE fish methodologies across Europe (common metrics) is unlikely by adapting or creating new fish indices but inter-comparison assessments are possible and valid using a common pressure index to harmonise diferente indices on a common scale. Research needs to be focused on more widely-applicable fish indices will require the formulation of completely new indices based on a more flexible use of fish metrics according to system typologies, relevance and, probably, an increased use of functional traits. For current indices, further research on a method of intercalibration is needed. Key Message 02: BQE Fish in TW respond consistently to human pressure gradients across transitional waters providing the means to assess Ecological Status (ES). Further work will be needed to identify those specific pressures affecting fish assemblages providing targets for minimising the effects of stress in mitigation and restoration plans. Key Message 03 Although the interpretation of outcomes is still difficult, more recente transitional fish indices are leading in the use of comprehensive appraisal and validation exercises to test the performance of BQEs in the assessment of Ecological Status (ES). Further appraisal of fish indices behaviour is needed to understand the meaning of the quality outcomes, to set realistic management targets and also to identify the aspects of the índices that are more likely to affect the outcomes leading to more robust and responsive indices Key Message 04 Uncertainty levels associated with metric variability in multi-metric fish indices can be managed to increase the confidence in Ecological Status (ES) class assignment. Further research is needed to include knowledge of habitat partition within systems, to understand metrics behaviour and precision, to test new combination rules allowing metric weighting by robustness and importantly to evaluate more robust sampling tools and methods. Key Message 05 Reference conditions for BQE fish-based quality assessments can be objectively estimated using predictive modelling. Further refinements will require the use of better pressure proxies, robust metrics amenable to modelling and to account for survey design bias (effort & choice of sampling gear) at the relevant scales used in monitoring programmes.info:eu-repo/semantics/publishedVersio

Comparison of different strategies for using fossil calibrations to generate the time prior in Bayesian molecular clock dating.

Fossil calibrations are the utmost source of information for resolving the distances between molecular sequences into estimates of absolute times and absolute rates in molecular clock dating analysis. The quality of calibrations is thus expected to have a major impact on divergence time estimates even if a huge amount of molecular data is available. In Bayesian molecular clock dating, fossil calibration information is incorporated in the analysis through the prior on divergence times (the time prior). Here, we evaluate three strategies for converting fossil calibrations (in the form of minimum- and maximum-age bounds) into the prior on times, which differ according to whether they borrow information from the maximum age of ancestral nodes and minimum age of descendent nodes to form constraints for any given node on the phylogeny. We study a simple example that is analytically tractable, and analyze two real datasets (one of 10 primate species and another of 48 seed plant species) using three Bayesian dating programs: MCMCTree, MrBayes and BEAST2. We examine how different calibration strategies, the birth-death process, and automatic truncation (to enforce the constraint that ancestral nodes are older than descendent nodes) interact to determine the time prior. In general, truncation has a great impact on calibrations so that the effective priors on the calibration node ages after the truncation can be very different from the user-specified calibration densities. The different strategies for generating the effective prior also had considerable impact, leading to very different marginal effective priors. Arbitrary parameters used to implement minimum-bound calibrations were found to have a strong impact upon the prior and posterior of the divergence times. Our results highlight the importance of inspecting the joint time prior used by the dating program before any Bayesian dating analysis.This research was funded by Biotechnology and Biosciences Research Council (UK) grant (BB/N000609/1) and Natural Environment Research Council (UK) grant (NE/N002067/1). J.B.-M. was supported by a CONACyT-Mexico and UCL scholarship

NLO Production and Decay of Quarkonium

We present a calculation of next-to-leading-order (NLO) QCD corrections to total hadronic production cross sections and to light-hadron-decay rates of heavy quarkonium states. Both colour-singlet and colour-octet contributions are included. We discuss in detail the use of covariant projectors in dimensional regularization, the structure of soft-gluon emission and the overall finiteness of radiative corrections. We compare our approach with the NLO version of the threshold-expansion technique recently introduced by Braaten and Chen. Most of the results presented here are new. Others represent the first independent reevaluation of calculations already known in the literature. In this case a comparison with previous findings is reported.Comment: 65 pages, Latex, epsfig, 8 figures. Typos corrected and improvements made to the text. Version to appear on Nucl Phys.

Characterization of the uncertainty of divergence time estimation under relaxed molecular clock models using multiple loci.

Genetic sequence data provide information about the distances between species or branch lengths in a phylogeny, but not about the absolute divergence times or the evolutionary rates directly. Bayesian methods for dating species divergences estimate times and rates by assigning priors on them. In particular, the prior on times (node ages on the phylogeny) incorporates information in the fossil record to calibrate the molecular tree. Because times and rates are confounded, our posterior time estimates will not approach point values even if an infinite amount of sequence data are used in the analysis. In a previous study we developed a finite-sites theory to characterize the uncertainty in Bayesian divergence time estimation in analysis of large but finite sequence data sets under a strict molecular clock. As most modern clock dating analyses use more than one locus and are conducted under relaxed clock models, here we extend the theory to the case of relaxed clock analysis of data from multiple loci (site partitions). Uncertainty in posterior time estimates is partitioned into three sources: Sampling errors in the estimates of branch lengths in the tree for each locus due to limited sequence length, variation of substitution rates among lineages and among loci, and uncertainty in fossil calibrations. Using a simple but analogous estimation problem involving the multivariate normal distribution, we predict that as the number of loci ([Formula: see text]) goes to infinity, the variance in posterior time estimates decreases and approaches the infinite-data limit at the rate of 1/[Formula: see text], and the limit is independent of the number of sites in the sequence alignment. We then confirmed the predictions by using computer simulation on phylogenies of two or three species, and by analyzing a real genomic data set for six primate species. Our results suggest that with the fossil calibrations fixed, analyzing multiple loci or site partitions is the most effective way for improving the precision of posterior time estimation. However, even if a huge amount of sequence data is analyzed, considerable uncertainty will persist in time estimates.This work was supported by a grant from the Biotechnological and Biological Sciences Research Council (BB/J009709/1) to Z.Y., and grants from Natural Science Foundation of China (31301093, 11301294 and 11201224) to T.Z