Biomedical subjects

Brenda F Kurland

Publications and source records attributed to Brenda F Kurland.

5 recordsLinked to original sources

PubMed2006

Longitudinal change in positive affect in community-dwelling older persons.

OBJECTIVES: To determine whether positive affect, defined as emotional contentment and happiness, remains stable in late life and to identify predictors of longitudinal change in positive affect. DESIGN: Longitudinal observational study. SETTING: Community. PARTICIPANTS: Six hundred sixty-three individuals aged 70 and older without disability at baseline and free of chronically depressed mood. MEASUREMENTS: Positive affect, social network, social activity, chronic health conditions, activities of daily living, instrumental activities of daily living (IADLs), cognitive functioning, and negative affect measured over 54 months, at 18-month intervals, up to four times. RESULTS: Positive affect remained relatively stable over 4.5 years of follow-up. Higher average levels of social activity and lower levels of negative affect were associated with higher positive affect. An increase of 1 point in negative affect (on a 7-point scale) was associated with a 0.23-point concurrent decrease in positive affect (on a 5-point scale). Needing help in an additional IADL was associated with a decrease in positive affect of 0.04 points. A greater number of chronic conditions at enrollment was associated with lower positive affect. CONCLUSION: Positive affect is directly correlated with social involvement and inversely correlated with negative affect, IADL functioning, and comorbidity. Positive affect was mostly related to factors that do not change over time, although it showed some sensitivity to short- and long-term changes in physical health and functioning.

Activities of Daily Living↗

PubMed2005

Directly parameterized regression conditioning on being alive: analysis of longitudinal data truncated by deaths.

For observational longitudinal studies of geriatric populations, outcomes such as disability or cognitive functioning are often censored by death. Statistical analysis of such data may explicitly condition on either vital status or survival time when summarizing the longitudinal response. For example a pattern-mixture model characterizes the mean response at time t conditional on death at time S = s (for s > t), and thus uses future status as a predictor for the time t response. As an alternative, we define regression conditioning on being alive as a regression model that conditions on survival status, rather than a specific survival time. Such models may be referred to as partly conditional since the mean at time t is specified conditional on being alive (S > t), rather than using finer stratification (S = s for s > t). We show that naive use of standard likelihood-based longitudinal methods and generalized estimating equations with non-independence weights may lead to biased estimation of the partly conditional mean model. We develop a taxonomy for accommodation of both dropout and death, and describe estimation for binary longitudinal data that applies selection weights to estimating equations with independence working correlation. Simulation studies and an analysis of monthly disability status illustrate potential bias in regression methods that do not explicitly condition on survival.

Activities of Daily Living↗

PubMed2004

Marginalized transition models for longitudinal binary data with ignorable and non-ignorable drop-out.

We extend the marginalized transition model of Heagerty to accommodate non-ignorable monotone drop-out. Using a selection model, weakly identified drop-out parameters are held constant and their effects evaluated through sensitivity analysis. For data missing at random (MAR), efficiency of inverse probability of censoring weighted generalized estimating equations (IPCW-GEE) is as low as 40 per cent compared to a likelihood-based marginalized transition model (MTM) with comparable modelling burden. MTM and IPCW-GEE regression parameters both display misspecification bias for MAR and non-ignorable missing data, and both reduce bias noticeably by improving model fit.

Antipsychotic Agents↗

PubMed2003

Prognostic effect of prior disability episodes among nondisabled community-living older persons.

The objective of this prospective cohort study, conducted in 1998-2002 in New Haven, Connecticut, was to determine the prognostic effect of prior episodes of disability. The analytical sample included 580 community-living persons aged 71 years or older who were nondisabled during an 18-month face-to-face assessment (i.e., zero-time). During monthly telephone interviews, participants were assessed for disability in activities of daily living. The primary explanatory variable was a history of disability in the year prior to zero-time as determined from the monthly interviews. The primary outcome was time to onset of disability over a 3-year period subsequent to zero-time. In Cox proportional hazards analyses that adjusted for several potential confounders, a prior history of disability was found to be significantly associated with development of any disability (i.e., > or = 1 month) and persistent disability (i.e., > or = 2 months); hazard ratios were 2.0 (95% confidence interval: 1.4, 2.7) and 2.0 (95% confidence interval: 1.3, 2.9), respectively. These strong associations were maintained after participants who had a prior history of chronic disability were excluded. Results demonstrate the long-term, deleterious effect of short-term disability among community-living older persons. More frequent assessments of functional status may be warranted in epidemiologic studies and clinical trials when disability is a primary focus.

Activities of Daily Living↗

PubMed2002

A 3-dimensional analysis of molar movement during headgear treatment.

Superimposition of serial cephalograms provides a limited description of tooth movement that could be complemented by data obtained from serial dental casts. The aim of this study was to develop a mathematical method for superimposing 3-dimensional data obtained from selected landmarks on longitudinally collected dental casts to describe maxillary first molar movement during headgear treatment. The material consisted of dental casts taken bimonthly from 36 children whose Class II Division 1 malocclusion was treated with straight-pull headgear during a 24-month period. Control data were collected from initial and final models of 38 subjects with a similar malocclusion who were not treated during a 24-month observation period. Spatial data from each subject's initial model were oriented similarly in an anatomically derived coordinate system, and a best-fit superimposition of palatal rugae landmarks from subsequent models allowed the measurement of molar movement. On average, headgear treatment resulted in distal movement of the molars, and the fitted net difference between treated and control subjects was 3.00 mm (SE, 0.37 mm; P < .001). Also, the headgear caused significantly more molar extrusion (0.56 mm; SE, 0.20 mm; P < .006) and buccal expansion (0.58 mm; SE, 0.17 mm; P < .001) on average than in the control group. Poor reliability of the method for measuring molar rotations indicated that they could not be determined accurately. Longitudinal description of molar movement for each subject revealed great individual variability in the amount and pattern of tooth movement. Several reasons could account for the wide range of individual variation and warrant exploration.

Case-Control Studies↗