Social-cognitive determinants of physical activity: The influence of social support, self-efficacy, outcome expectations, and self-regulation among participants in a church-based health promotion study.

A social-cognitive model of physical activity was tested, using structural equation analysis of data from 999 adults (21% African American; 66% female; 38% inactive) recruited from 14 southwestern Virginia churches participating in the baseline phase of a health promotion study. Within the model, age, race, social support, self-efficacy, and self-regulation contributed to participants' physical activity levels, but outcome expectations did not. Of the social-cognitive variables, self-regulation exerted the strongest effect on physical activity. Independent of self-regulation, self-efficacy had little effect. Social support influenced physical activity as a direct precursor to self-efficacy and self-regulation. The model provided a good fit to the data and explained 46% of the variance in physical activity among the diverse group of adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prospective memory and apolipoprotein e in healthy aging and early stage Alzheimer's disease.

The present study examined whether prospective memory performance discriminates healthy aging from very mild dementia of the Alzheimer type (DAT) and individuals at risk for DAT because of the presence of the apolipoprotein E (ApoE) ε4 allele. Four groups (young subjects, young-old control subjects, old-old control subjects, and subjects with very mild DAT) engaged in an event-based prospective memory task wherein they responded to a specific word embedded in a general knowledge test. Results indicated that prospective memory performance was clearly impaired in the very mild DAT group relative to the healthy older control groups. Moreover, prospective memory performance appears to capture unique variance in discriminating these 2 groups above and beyond standard retrospective memory tests. However, prospective memory was not affected by ApoE status in the young-old control group and, contrary to predictions, the ε4+ old-old control subjects showed better performance than did the ε4- subjects. In contrast to the healthy individuals, in the very mild DAT group, ε4+ subjects showed deficits in performance relative to the ε4- subjects. Discussion focuses on prospective memory as a cognitive indicator of early stage DAT. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analysis of repeated measures data with clumping at zero

Longitudinal or repeated measures data with clumping at zero occur in many applications in biometrics, including health policy research, epidemiology, nutrition, and meteorology. These data exhibit correlation because they are measured on the same subject over time or because subjects may be considered repeated measures within a larger unit such as a family. They present special challenges because of the extreme non-normality of the distributions involved. A model for repeated measures data with clumping at zero, using a mixed-effects mixed-distribution model with correlated random effects, is presented. The model contains components to model the probability of a nonzero value and the mean of nonzero values, allowing for repeated measurements using random effects and allowing for correlation between the two components. Methods for describing the effect of predictor variables on the probability of nonzero values, on the mean of nonzero values, and on the overall mean amount are given. This interpretation also applies to the mixed-distribution model for cross-sectional data. The proposed methods are illustrated with analyses of effects of several covariates on medical expenditures in 1996 for subjects clustered within households using data from the Medical Expenditure Panel Survey.