The Truth behind the Zeros: A New Approach to Principal Component Analysis of the Neuropsychiatric Inventory.

Psychiatric syndromes in dementia are often derived from the Neuropsychiatric Inventory (NPI) using principal component analysis (PCA). The validity of this statistical approach can be questioned, since the excessive proportion of zeros and skewness of NPI items may distort the estimated relations between the items. We propose a novel version of PCA, ZIBP-PCA, where a zero-inflated bivariate Poisson (ZIBP) distribution models the pairwise covariance between the NPI items.

Serum Potassium Is Associated with Cognitive Decline in Patients with Lewy Body Dementia.

Background: Epidemiological studies link serum potassium (K+) to cognitive performance, but whether cognitive prognosis in dementia is related to K+ levels is unknown.

Objective: To determine if K+ levels predict cognitive prognosis in dementia and if this varies according to diagnosis or neuropathological findings.

Methods: This longitudinal cohort study recruited 183 patients with mild Alzheimer's disease or Lewy body dementia (LBD).

Fridge: Focused fine-tuning of ridge regression for personalized predictions.

Statistical prediction methods typically require some form of fine-tuning of tuning parameter(s), with K-fold cross-validation as the canonical procedure. For ridge regression, there exist numerous procedures, but common for all, including cross-validation, is that one single parameter is chosen for all future predictions. We propose instead to calculate a unique tuning parameter for each individual for which we wish to predict an outcome.

Integrative clustering of high-dimensional data with joint and individual clusters.

When measuring a range of genomic, epigenomic, and transcriptomic variables for the same tissue sample, an integrative approach to analysis can strengthen inference and lead to new insights. This is also the case when clustering patient samples, and several integrative cluster procedures have been proposed. Common for these methodologies is the restriction to a joint cluster structure, equal in all data layers.