Global odds model with proportional odds and trend odds applied to gross and microscopic brain infarcts

<p>Medical and epidemiological researchers commonly study ordinal measures of symptoms or pathology. Some of these studies involve two correlated ordinal measures. There is often an interest in including both measures in the modeling. It is common to see analyses that consider one of the measures as a predictor in the model for the other measure as an outcome. There are, however, issues with these analyses including a biased estimate of the probabilities and a decreased power due to multicollinearity (since they share some predictors). These issues create a necessity to examine both variables as simultaneous outcomes, by assessing the marginal probabilities for each outcome (i.e. using a proportional odds model) and the association between the two outcomes (i.e. using a constant global odds model). In this work, we extend this model using a parsimonious option when the constraints imposed by assumptions of proportional marginal odds and constant global odds do not hold. We compare approaches by using simulations and by analyzing data on brain infarcts in older adults. Age at death is a marginal predictor of gross infarcts and also a marginal predictor of microscopic infarcts, but does not modify the association between gross and microscopic infarcts.</p

Ex-vivo magnetic susceptibility as a function of in-vivo magnetic susceptibility.

<p>Plot of regional gray matter magnetic susceptibility values measured ex-vivo as a function of the corresponding susceptibility values measured in-vivo in the same hemispheres, for all hemispheres of Dataset 2. Each point in the scatter plot represents a single gray matter brain region of a single hemisphere. Ex-vivo magnetic susceptibility values shown in the plot have been corrected for the effects of lower temperature during ex-vivo imaging [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0188395#pone.0188395.ref004" target="_blank">4</a>].</p

Postmortem brain hemisphere in imaging container.

<p>Example of a participant’s brain hemisphere submerged in formaldehyde solution.</p

Correspondence of in-vivo and ex-vivo data within the same participants.

<p>In-vivo and ex-vivo magnetic susceptibility and gradient-echo magnitude maps for a section of the basal ganglia of three hemispheres from Dataset 2 imaged both in-vivo and ex-vivo.</p

Dataset 1 characteristics.

<p>Dataset 1 characteristics.</p

Voxel-wise differences in magnetic susceptibility maps of consecutive time-points.

<p>Ex-vivo magnetic susceptibility difference maps between consecutive time-points, for all hemispheres of Dataset 1. The corresponding susceptibility map and spin-echo image of the last time-point are displayed on the rightmost two columns. Note: For hemisphere D, the difference map marked with an asterisk represents the difference between the third and fifth time-points.</p

Measurements from 3T as a function of measurements from 1.5T.

<p>Plot of magnetic susceptibility in selected gray and white matter regions of the same hemisphere imaged postmortem using both in-vivo (1.5T) and ex-vivo (3T) QSM methods (Dataset 3).</p

Ex-vivo magnetic susceptibility maps.

<p>Examples of axial ex-vivo magnetic susceptibility maps of human brain hemispheres from five participants.</p

Magnetic susceptibility over time postmortem for gray and white matter regions.

<p>Plots of ex-vivo magnetic susceptibility in selected gray and white matter regions as a function of time postmortem, for all hemispheres of Dataset 1. Error bars around individual data points represent the 95% confidence interval of the susceptibility values within the region at that specific time point.</p

Cognitive Decline in Older Persons Initiating Anticholinergic Medications

<div><p>Background</p><p>This study examines the effect of initiating medications with anticholinergic activity on the cognitive functions of older persons.</p><p>Methods</p><p>Participants were 896 older community-dwelling, Catholic clergy without baseline dementia. Medication data was collected annually. The Anticholinergic Cognitive Burden Scale was utilized to identify use of a medication with probable or definite anticholinergic activity. Participants had at least two annual cognitive evaluations.</p><p>Results</p><p>Over a mean follow-up of 10 years, the annual rate of global cognitive function decline for never users, prevalent users, and incident users was −0.062 (SE = 0.005), −0.081(SE = 0.011), and −0.096 (SE = 0.007) z-score units/year, respectively. Compared to never users, incident users had a more rapid decline (difference = −0.034 z-score units/year, SE = 0.008, p<0.001) while prevalent users did not have a significantly more rapid decline (p = 0.1).</p><p>Conclusions</p><p>Older persons initiating a medication with anticholinergic activity have a steeper annual decline in cognitive functioning than those who are not taking these medications.</p></div