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257 results on '"Frangakis, Constantine E."'

2. Estimation of Treatment Effects in Matched-Pair Cluster Randomized Trials by Calibrating Covariate Imbalance between Clusters

Author

Wu, Zhenke, Frangakis, Constantine E., Louis, Thomas A., and Scharfstein, Daniel O.

Subjects
Statistics - Methodology
Abstract

We address estimation of intervention effects in experimental designs in which (a) interventions are assigned at the cluster level; (b) clusters are selected to form pairs, matched on observed characteristics; and (c) intervention is assigned to one cluster at random within each pair. One goal of policy interest is to estimate the average outcome if all clusters in all pairs are assigned control versus if all clusters in all pairs are assigned to intervention. In such designs, inference that ignores individual level covariates can be imprecise because cluster-level assignment can leave substantial imbalance in the covariate distribution between experimental arms within each pair. However, most existing methods that adjust for covariates have estimands that are not of policy interest. We propose a methodology that explicitly balances the observed covariates among clusters in a pair, and retains the original estimand of interest. We demonstrate our approach through the evaluation of the Guided Care program., Comment: 27 pages, 3 figures, 3 tables

Published
2014
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14. Sunshine and Suicide Incidence

Author

Voracek, Martin, Fisher, Maryanne L., Skalkidou, Alkistis, Papadopoulos, Fotios C., Petridou, Eleni, Trichopoulos, Dimitrios, and Frangakis, Constantine E.

Published
2002

17. Is Sertraline Treatment or Depression Remission in Depressed Alzheimer Patients Associated with Improved Caregiver Well Being? Depression in Alzheimer's Disease Study 2

Author

Flynn Longmire, Crystal V., Drye, Lea T., Frangakis, Constantine E., Martin, Barbara K., Meinert, Curtis L., Mintzer, Jacobo E., Munro, Cynthia A., Porsteinsson, Anton P., Rabins, Peter V., Rosenberg, Paul B., Schneider, Lon S., Weintraub, Daniel, and Lyketsos, Constantine G.

Published
2014
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20. Specificity in Generalization Effects of Transcranial Direct Current Stimulation Over the Left Inferior Frontal Gyrus in Primary Progressive Aphasia

Author

Wang, Zeyi, primary, Ficek, Bronte N., additional, Webster, Kimberly T., additional, Herrmann, Olivia, additional, Frangakis, Constantine E., additional, Desmond, John E., additional, Onyike, Chiadi U., additional, Caffo, Brian, additional, Hillis, Argye E., additional, and Tsapkini, Kyrana, additional

Published
2022
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33. The long-term relationship between high-intensity volunteering and physical activity in older African American women

Author

Tan, Erwin J., Rebok, George W., Yu, Qilu, Frangakis, Constantine E., Carlson, Michelle C., Wang, Tao, Ricks, Michelle, Tanner, Elizabeth K., McGill, Sylvia, and Fried, Linda P.

Subjects
African American aged -- Physiological aspects, Exercise -- Physiological aspects, Wellness programs -- Usage, Health, Psychology and mental health, Seniors
Abstract

Objectives. Experience Corps (EC) places older volunteers in public elementary schools in 20 cities across the country. The EC program in Baltimore is a health promotion intervention designed to improve the academic outcomes of children and increase older adult volunteer physical activity. We sought to determine if there were sustained increases in physical activity with participation in EC. Methods. Seventy-one African American women volunteers in the Baltimore EC were compared with 150 African American women in the Women's Health and Aging Studies (WHAS) I and II; all were aged 65-86 years with comparable Social Economic Status, frailty, and self reported health status. Using a regression model, we evaluated physical activity adjusting for a propensity score and time of follow-up over 3 years. Results. EC volunteers reported a sustained increase in physical activity as compared with the comparison cohort. Baseline physical activity for individuals with a median propensity score was 420 kcal/wk for both groups. At 36 months. EC volunteers reported 670 kcal/week compared with 410 kcal/week in WHAS (p = .04). Discussion. These findings suggest that high-intensity senior service programs that are designed as health promotion interventions could lead to sustained improvements in physical activity in high-risk older adults, while simultaneously addressing important community needs. Key Words: African Americans--Community-based participatory research--Elderly--Health disparity--Intergenerational social contract--Physical activity--Volunteerism--Women

Published
2009

34. Design of Depression in Alzheimer's Disease Study-2

Author

Martin, Barbara K., Frangakis, Constantine E., Rosenberg, Paul B., Mintzer, Jacobo E., Katz, Ira R., Porsteinsson, Anton P., Schneider, Lon S., Rabins, Peter V., Munro, Cynthia A., Meinert, Curtis L., Niederehe, George, and Lyketsos, Constantine G.

Published
2006
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47. The method of envelopes to concisely calculate semiparametric efficient scores under parametric restrictions.

Author

Frangakis, Constantine E.

Subjects
DOCTORAL students, INTUITION
Abstract

When addressing semiparametric problems with parametric restrictions (assumptions on the distribution), the efficient score (ES) of a parameter is often important for generating useful estimates. However, usual derivation of ES, although conceptually simple, is often lengthy and with many steps that do not help in understanding why its final form arises. This drawback often casts onto semiparametric estimation a mantle that can turn away otherwise able doctoral students or researchers. Here we show that many ESs can be obtained as a one-step derivation after we characterize those features (envelopes) of the unrestricted problem that are constrained in the restricted problem. We demonstrate our arguments in three problems with known ES but whose usual derivations are lengthy. We show that the envelope-based derivation is dramatically explanatory and compact, needing essentially two lines where the standard approach needs 10 or more pages. This suggests that the envelope method can add useful intuition and exegesis to both teaching and research of semiparametric estimation. [ABSTRACT FROM AUTHOR]

Published
2021
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48. Comment

Author

Rubin, Donald B. and Frangakis, Constantine E.

Subjects
Longitudinal method -- Models, Prevalence studies (Epidemiology) -- Models, Mathematics
Abstract

A critique on Robins, Greenland and Hu's study on causal effects of a time-dependent exposure or treatment is presented. They used Rubin's model in examining causal effects but their approach should have made better use of existing literature and terminology. This would also have allowed further examination of broad issues that arise in observational studies. They could also have used other assumptions that increase the efficiency of estimation but retain the identifiability of causal effects., We congratulate Robins, Greenland, and Hu (RGH) for this article, which offers important ideas and methods for causal inference from longitudinal, observational data. The statistical formalization of causal inference from [...]

Published
1999

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