An estimating equations approach to fitting latent exposure models with longitudinal health outcomes

The analysis of data arising from environmental health studies which collect a large number of measures of exposure can benefit from using latent variable models to summarize exposure information. However, difficulties with estimation of model parameters may arise since existing fitting procedures for linear latent variable models require correctly specified residual variance structures for unbiased estimation of regression parameters quantifying the association between (latent) exposure and health outcomes. We propose an estimating equations approach for latent exposure models with longitudinal health outcomes which is robust to misspecification of the outcome variance. We show that compared to maximum likelihood, the loss of efficiency of the proposed method is relatively small when the model is correctly specified. The proposed equations formalize the ad-hoc regression on factor scores procedure, and generalize regression calibration. We propose two weighting schemes for the equations, and compare their efficiency. We apply this method to a study of the effects of in-utero lead exposure on child development.Comment: Published in at http://dx.doi.org/10.1214/08-AOAS226 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Real impact is about influence, meaning and value: Mapping contributions for a new impact agenda in the humanities.

The humanities are driven both by epistemological and normative interests in a range of topics resulting in a complex topography of the public value of the humanities. But for the most part, its diffuse knowledge and impact has been defined and restricted to inputs and outputs. David Budtz Pedersen presents an overview of a research project aiming to reveal the pathways of humanities research deeply integrated in the functioning and affluence of modern liberal societies

Overhyped and concentrated investments in research funding are leading to unsustainable science bubbles.

David Budtz Pedersen examines how the scientific market exhibits bubble behaviour similar to that of financial markets. Taking as an example the overwhelming investments in neuroscience, such high expectations may actually drain the research system from resources and new ideas. In the end the permanent competition for funding and the lack of ‘risk diversification’, might generate a climate in which citizens and policymakers lose their confidence in science as they did with the financial sector after the 2008 crash

Clot retraction

The haemorrhagic disorders form only a small, although often most alarming part of the diseases inflicted upon mankind, and in spite of the enthusiasm of the disproportionally great number of workers investigating the problem of the coagulation of the blood, this problem until quite recently could only be looked upon as being mainly of academic physiological interest. With the advent and daily increasing use of the highly dangerous anti-coagulant therapy for thrombosis and embolism, demanding at least a general understanding of the mechanism of blood clotting, every aspect of this mechanism has become of practical clinical importance, and no serious effort to clarify the question can be considered wasted. It is peculiar that the last phase of coagulation, the contraction of the clot, which is by no means the least spectacular, has received rather scanty attention compared to the enormous amount of work that has been expended on the earlier stages. No agreement exists with regard to the mechanism or purpose of clot retraction; the factors controlling it are to a large-extent unknown, and even the fundamental question of the part played by the platelets is undecided

Thalassaemia-haemoglobin E disease in a Cape coloured family

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