Robitaille et al., 2013. Longitudinal mediation of processing speed on age-related change in memory and fluid intelligence.

Robitaille, A., Piccinin, A. M., Muniz-Terrera, G., Hoffman, L., Johansson, B., Deeg, D. J., Aartsen, M.J., Comijs, H.C. & Hofer, S. M. (2013). Longitudinal mediation of processing speed on age-related change in memory and fluid intelligence. Psychology and aging, 28(4), 887.

Year: 
2013
Status: 
complete
Abstract: 

Age-related decline in processing speed has long been considered a key driver of cognitive aging. While the majority of empirical evidence for the processing speed hypothesis has been obtained from analyses of between-person age differences, longitudinal studies provide a direct test of within-person change. Using recent developments in longitudinal mediation analysis, we examine the speed—mediation hypothesis at both the within-and between-person levels in two longitudinal studies, Longitudinal Aging Study Amsterdam (LASA) and Origins of Variance in the Oldest-Old (OCTO-Twin). We found significant within-person indirect effects of change in age, such that increasing age was related to lower speed, which in turn relates to lower performance across repeated measures on other cognitive outcomes. Although between-person indirect effects were also significant in LASA, they were not in OCTO-Twin which is not unexpected given the age homogeneous nature of the OCTO-Twin data. A more in-depth examination through measures of effect size suggests that, for the LASA study, the within-person indirect effects were small and between-person indirect effects were consistently larger. These differing magnitudes of direct and indirect effects across levels demonstrate the importance of separating between- and within-person effects in evaluating theoretical models of age-related change. (PsycINFO Database Record (c) 2016 APA, all rights reserved)

Piccinin et al., 2013. Coordinated analysis of age, sex, and education effects on change in MMSE scores

Piccinin, A. M., Muniz-Terrera, G., Clouston, S., Reynolds, C. A., Thorvaldsson, V., Deary, I. J., Deeg, DJ, Johansson, B., Mackinnon, A., Spiro, A., & Starr, J. M. (2012). Coordinated analysis of age, sex, and education effects on change in MMSE scores. Journals of Gerontology Series B: Psychological Sciences and Social Sciences, 68(3), 374-390.

Year: 
2013
Status: 
complete
Abstract: 

Objectives. We describe and compare the expected performance trajectories of older adults on the Mini-Mental Status Examination (MMSE) across six independent studies from four countries in the context of a collaborative network of longitudinal studies of aging. A coordinated analysis approach is used to compare patterns of change conditional on sample composition differences related to age, sex, and education. Such coordination accelerates evaluation of particular hypotheses. In particular, we focus on the effect of educational attainment on cognitive decline.

Method. Regular and Tobit mixed models were fit to MMSE scores from each study separately. The effects of age, sex, and education were examined based on more than one centering point.

Results. Findings were relatively consistent across studies. On average, MMSE scores were lower for older individuals and declined over time. Education predicted MMSE score, but, with two exceptions, was not associated with decline in MMSE over time.

Conclusion. A straightforward association between educational attainment and rate of cognitive decline was not supported. Thoughtful consideration is needed when synthesizing evidence across studies, as methodologies adopted and sample characteristics, such as educational attainment, invariably differ.

Rast et al., 2014. The identification of regions of significance in the effect of multimorbidity on depressive symptoms using longitudinal data: an application of the Johnson-Neyman technique.

Rast, P., Rush, J., Piccinin, A., & Hofer, S. M. (2014). The identification of regions of significance in the effect of multimorbidity on depressive symptoms using longitudinal data: An application of the Johnson-Neyman technique. Gerontology60(3), 274-281.

Year: 
2014
Status: 
complete
Abstract: 

Background: The investigation of multimorbidity and aging is complex and highly intertwined with aging-related changes in physical and cognitive capabilities, and mental health and is known to affect psychological distress and quality of life. Under these circumstances it is important to understand how the effects of chronic conditions evolve over time relative to aging-related and end-of-life changes. The identification of periods in time where multimorbidity impacts particular outcomes such as depressive symptoms, versus periods of time where this is not the case, reduces the complexity of the phenomenon. 

Objective: We present the Johnson-Neyman (JN) technique in the context of a curvilinear longitudinal model with higher-order terms to probe moderatorst and to identify regions of statistical significance. In essence, the JN technique allows one to identify conditions under which moderators impact an outcome from conditions where these effects are not significant. 

Methods: To illustrate the use of the JN technique in a longitudinal sample, we used data from the Health and Retirement Study. Analyses were based on time-to-death models including participants who died within the study duration of 12 years. 

Results: Multimorbidity differentially affects rates of change in depression. For some periods in time the effects are statistically significant while in other periods the same effects are not statistically different from zero. 

Conclusion: The JN technique is useful to continuously probe moderating effects and to identify particular interactions with the model for time when certain effects are or are not statistically significant. In the context of multimorbidity this method is particularly useful for interpreting the complex interactions with differential change over time.

Muniz-Terrera et al., 2012. Investigating terminal decline: results from a UK population-based study of aging.

Muniz-Terrera, G., van den Hout, A., Piccinin, A. M., Matthews, F. E., & Hofer, S. M. (2013). Investigating terminal decline: Results from a UK population-based study of aging. Psychology and aging, 28(2), 377.

Year: 
2012
Status: 
complete
Abstract: 

The terminal decline hypothesis states that in the proximity of death, an individual’s decline in cognitive abilities accelerates. We aimed at estimating the onset of faster rate of decline in global cognition using Mini Mental State Examination (MMSE) scores from participants of the Cambridge City over 75 Cohort Study (CC75C), a U.K. population-based longitudinal study of aging where almost all participants have died. The random change point model fitted to MMSE scores structured as a function of distance to death allowed us to identify a potentially different onset of change in rate of decline before death for each individual in the sample. Differences in rate of change before and after the onset of change in rate of decline by sociodemographic variables were investigated. On average, the onset of a faster rate of change occurred about 7.7 years before death and varied across individuals. Our results show that most individuals experience a period of slight decline followed by a much sharper decline. Education, age at death, and cognitive impairment at study entry were identified as modifiers of rate of change before and after change in rate of decline. Gender differences were found in rate of decline in the final stages of life. Our study suggests that terminal decline is a heterogeneous process, with its onset varying between individuals. (PsycINFO Database Record (c) 2016 APA, all rights reserved)

Clouston et al., 2015. Educational Inequalities in Health Behaviors at Midlife: Is There a Role for Early-life Cognition?

Clouston, S. A., Richards, M., Cadar, D., & Hofer, S. M. (2015). Educational inequalities in health behaviors at midlife: Is there a role for early-life cognition? Journal of health and social behavior, 56(3), 323-340.

Year: 
2015
Status: 
complete
Abstract: 

Education is a fundamental cause of social inequalities in health because it influences the distribution of resources, including money, knowledge, power, prestige, and beneficial social connections, that can be used in situ to influence health. Recent studies have highlighted early-life cognition as commonly indicating the propensity for educational attainment and determining health and age of mortality. Health behaviors provide a plausible mechanism linking both education and cognition to later-life health and mortality. We examine the role of education and cognition in predicting smoking, heavy drinking, and physical inactivity at midlife using data from the Wisconsin Longitudinal Study (N = 10,317), National Survey of Health and Development (N = 5,362), and National Childhood Development Study (N = 16,782). Adolescent cognition was associated with education but was inconsistently associated with health behaviors. Education, however, was robustly associated with improved health behaviors after adjusting for cognition. Analyses highlight structural inequalities over individual capabilities when studying health behaviors.

Clouston et al., 2015. Educational inequalities in aging-related declines in fluid cognition and the onset of cognitive pathology

Clouston, S. A., Glymour, M. M., & Terrera, G. M. (2015). Educational inequalities in aging-related declines in fluid cognition and the onset of cognitive pathology. Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring, 1(3), 303-310.
Year: 
2015
Status: 
complete
Abstract: 

Background: Education has been robustly associated with cognitive reserve and dementia, but not with the rate of cognitive aging, resulting in some confusion about the mechanisms of cognitive aging. This study uses longitudinal data to differentiate between trajectories indicative of healthy versus pathologic cognitive aging.

Methods: Participants included 9401 Health and Retirement Study respondents aged ≥55 years who completed cognitive testing regularly over 17.3 years until most recently in 2012. Individual-specific random change-point modeling was used to identify age of incident pathologic decline; acceleration is interpreted as indicating likely onset of pathologic decline when it is significant and negative.

Results: These methods detect incident dementia diagnoses with specificity/sensitivity of 89.3%/44.3%, 5.6 years before diagnosis. Each year of education was associated with 0.09 (95% confidence interval [CI], 0.087–0.096; P < .001) standard deviation higher baseline cognition and delayed onset of cognitive pathology (hazard ratio, 0.98; 95% CI, 0.96–0.99; P = .006).

Conclusions: Longitudinal random change-point modeling was able to reliably identify incident dementia. Accounting for incident cognitive pathology, we find that education predicts cognitive capability and delayed onset pathologic declines.

Hofer, 2013. On the robustness of results from longitudinal observational studies: Integrative data analysis and designs for optimizing detection of within-person change.

Year: 
2013
Status: 
complete
Presentation Citations: 

Hofer, S. M. (October, 2013). On the robustness of results from longitudinal observational studies: Integrative data analysis and designs for optimizing detection of within-person change. Paper presented at the annual meeting of the Society of Multivariate Experimental Psychology, St. Pete Beach, FL.

Hofer et al., 2009. Patterns of between-person age differences and within-person changes in cognitive capabilities with age

Year: 
2009
Status: 
complete
Presentation Citations: 

Hofer, S. M., Piccinin, A. M., Bontempo, D. E., Sparks, C., & Hoffman, L. (2009, November). Integrative Analysis of Longitudinal Studies of Aging (IALSA): Patterns of between-person age differences and within-person changes in cognitive capabilities with age.  In S. M. Hofer (Chair), Coordinated and pooled data analyses of longitudinal studies of aging: Aging and dementia-related change in cognition, affect, and physical functioning. Paper symposium conducted at the annual meeting of the Gerontological Society of America, Atlanta.

Wray et al., 2010. Diabetes and cognition in midlife and older adulthood.

Year: 
2010
Status: 
complete
Presentation Citations: 

Wray, L., Alwin, D. F., Hofer, S. M., Zeisser, K. L., Chu, C-J. (2010, August). Diabetes and cognition in midlife and older adulthood.  Paper presented at the annual meeting of the American Sociological Association, Atlanta.

Wray, L., Alwin, D. F., Hofer, S. M., Zeisser, K. L., Chu, C-J. (2010, November). Diabetes and cognitive change in midlife and older adulthood.  Poster presented at the annual meeting of the Gerontological Society of America, New Orleans.

Hofer et al., 2010. Too stressed to think? An undergraduate course on multivariate design, data collection and analysis.

Year: 
2010
Status: 
complete
Presentation Citations: 

Hofer, S. M., Sparks, C. A., & MacDonald, S. W. S. (2010, October). Too stressed to think? An undergraduate course on multivariate design, data collection and analysis. Paper presented at the annual meeting of the Society of Multivariate Experimental Psychology, Atlanta

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