The Patient Activation Measure (PAM) quantifies the extent to which people are informed about and involved in their health care. Objectives were to determine the psychometric properties of PAM among multimorbid older adults and evaluate a theoretical, four-stage model of patient activation.
A cross-sectional analysis was used to assess the psychometric properties of PAM. Internal consistency was assessed using Cronbach α. Construct validity was evaluated using general linear modeling to compute associations between PAM scores and health-related behaviors, functional status, and health care quality. Latent class analysis was used to evaluate the theoretical four-stage structure of patient activation.
Participants in a randomized trial of Guided Care (N=855), a model of comprehensive health care for older adults with chronic conditions that put them at risk of using health services heavily during the coming year.
Higher PAM activation scores and stage were positively associated with higher functional status, health care quality, and adherence to some health behaviors. Latent class analysis supported the multistage theory of patient activation.
The PAM is a reliable, valid, and potentially clinically useful measure of patient activation for multimorbid older adults.
Patient activation; self-management; chronic conditions
Acute lung injury (ALI) is a condition characterized by acute onset of severe hypoxemia and bilateral pulmonary infiltrates. ALI patients typically require mechanical ventilation in an intensive care unit. Low tidal volume ventilation (LTVV), a time-varying dynamic treatment regime, has been recommended as an effective ventilation strategy. This recommendation was based on the results of the ARMA study, a randomized clinical trial designed to compare low vs. high tidal volume strategies (The Acute Respiratory Distress Syndrome Network, 2000) . After publication of the trial, some critics focused on the high non-adherence rates in the LTVV arm suggesting that non-adherence occurred because treating physicians felt that deviating from the prescribed regime would improve patient outcomes. In this paper, we seek to address this controversy by estimating the survival distribution in the counterfactual setting where all patients assigned to LTVV followed the regime. Inference is based on a fully Bayesian implementation of Robins’ (1986) G-computation formula. In addition to re-analyzing data from the ARMA trial, we also apply our methodology to data from a subsequent trial (ALVEOLI), which implemented the LTVV regime in both of its study arms and also suffered from non-adherence.
Bayesian inference; Causal inference; Dynamic treatment regime; G-computation formula
Missing phenotype data can be a major hurdle to mapping quantitative trait loci (QTL). Though in many cases experiments may be designed to minimize the occurrence of missing data, it is often unavoidable in practice; thus, statistical methods to account for missing data are needed. In this paper we describe an approach for conjoining multiple imputation and QTL mapping. Methods are applied to map genes associated with increased breathing effort in mice after lung inflammation due to allergen challenge in developing lines of the Collaborative Cross, a new mouse genetics resource. Missing data poses a particular challenge in this study because the desired phenotype summary to be mapped is a function of incompletely observed dose-response curves. Comparison of the multiple imputation approach to two naive approaches for handling missing data suggest that these simpler methods may yield poor results: ignoring missing data through a complete case analysis may lead to incorrect conclusions, while using a last observation carried forward procedure, which does not account for uncertainty in the imputed values, may lead to anti-conservative inference. The proposed approach is widely applicable to other studies with missing phenotype data.
multiple imputation; missing data; quantitative trait loci
The Patient Activation Measure (PAM) quantifies the extent to which people are informed about and involved in their health care. Objectives were to determine the psychometric properties of PAM among multi-morbid older adults and evaluate a theoretical, four-stage model of patient activation.
A cross-sectional analysis was used to assess the psychometric properties of PAM. Internal consistency was assessed using Cronbach’s alpha. Construct validity was evaluated using general linear modeling to compute associations between PAM scores and health-related behaviors, functional status and health care quality. Latent class analysis was used to evaluate the theoretical four-stage structure of patient activation.
Participants in a randomized trial of Guided Care (N = 855), a model of comprehensive health care for older adults with chronic conditions that put them at risk of using health services heavily during the coming year.
Higher PAM activation scores and stage were positively associated with higher functional status, health care quality, and adherence to some health behaviors. Latent class analysis supported the multi-stage theory of patient activation.
The PAM is a reliable, valid, and potentially clinically useful measure of patient activation for multi-morbid older adults.
Patient activation; self-management; chronic conditions
The optimal blood pressure level to minimize the risk of ischemic stroke (IS) in older adults is undetermined. Cerebral white matter lesions (WML), prevalent in older adults, may be a marker for vulnerability to IS. We aimed at determining the relationship between diastolic blood pressure (DBP) levels and IS in the presence of WML.
The Cardiovascular Health Study population (N = 3,345, age ≥ 65 years, N = 3,345) was followed between 1989 and 2002 for IS incidence. Survival analysis included quintiles of DBP analyzed within WML levels controlling for age and cardiovascular disease.
DBP had no effect on IS incidence in low WML levels but had a marginally significant J-curve relationship with IS in high WML levels: the adjusted hazard ratio for IS in the lowest (<63 mmHg) and highest (≥80) DBP quintiles compared with the third (nadir, 69–73 mmHg) was 1.64 (95% confidence interval: 0.93–2.9) and 1.83 (95% confidence interval: 1.06–3.15), respectively.
In older adults with low-grade WML, low DBP may not pose a risk for IS. However, in high-grade WML, IS risk may increase in DBP less than 69 mmHg but is highest more than 80 mmHg. People with high-grade WML may be at risk of IS in high and low DBP.
Ischemic stroke; White matter lesions; Blood pressure; Cardiovascular Health Study;
Purpose: Guided Care (GC) is a model of health care for multimorbid older adults that is provided by a registered nurse who works with the patients’ primary care physician (PCP). The purpose of this study was to determine whether GC improves patients’ primary caregivers’ depressive symptoms, strain, productivity, and perceptions of the quality of care recipients’ chronic illness care. Design and Methods: A cluster-randomized controlled trial of GC was conducted within 14 PCP teams. The study sample included 196 primary caregivers who completed baseline and 18-month surveys and whose care recipients remained alive and enrolled in the GC study for 18 months. Caregiver outcomes included the following: depressive symptoms (Center for Epidemiological Studies-Depression scale), strain (Modified Caregiver Strain Index), the quality of care recipients’ chronic illness care [Patient Assessment of Chronic Illness Care (PACIC)], and personal productivity (Work Productivity and Activity Impairment questionnaire, adapted for caregiving). Results: In multivariate regression models, between-group differences in depression, strain, work productivity, and regular activity productivity were not statistically significant after 18 months, but GC caregivers reported the overall quality of their recipients’ chronic illness care to be significantly higher (adjusted beta = 0.40, 95% confidence interval : 0.14–0.67). Quality was significantly higher in 4 of 5 PACIC subscales, reflecting the dimensions of goal setting, coordination of care, decision support, and patient activation. Implications: GC improved the quality of chronic illness care received by multimorbid care recipients but did not improve caregivers’ depressive symptoms, affect, or productivity.
Caregiving; Chronic disease; Nursing; Primary care; Guided Care
The quality of health care for older Americans with chronic conditions is suboptimal.
To evaluate the effects of “Guided Care” on patient-reported quality of chronic illness care.
Cluster-randomized controlled trial of Guided Care in 14 primary care teams.
Older patients of these teams were eligible to participate if, based on analysis of their recent insurance claims, they were at risk for incurring high health-care costs during the coming year. Small teams of physicians and their at-risk older patients were randomized to receive either Guided Care (GC) or usual care (UC).
“Guided Care” is designed to enhance the quality of health care by integrating a registered nurse, trained in chronic care, into a primary care practice to work with 2–5 physicians in providing comprehensive chronic care to 50–60 multi-morbid older patients.
Eighteen months after baseline, interviewers blinded to group assignment administered the Patient Assessment of Chronic Illness Care (PACIC) survey by telephone. Logistic and linear regression was used to evaluate the effect of the intervention on patient-reported quality of chronic illness care.
Of the 13,534 older patients screened, 2,391 (17.7%) were eligible to participate in the study, of which 904 (37.8%) gave informed consent and were cluster-randomized. After 18 months, 95.3% and 92.2% of the GC and UC recipients who remained alive and eligible completed interviews. Compared to UC recipients, GC recipients had twice greater odds of rating their chronic care highly (aOR = 2.13, 95% CI = 1.30–3.50, p = 0.003).
Guided Care improves self-reported quality of chronic health care for multi-morbid older persons.
quality of care; chronic illness; older
The Guided Care Program for Families and Friends (GCPFF) is one component of “Guided Care” (GC), a model of primary care for chronically ill older adults that is facilitated by a registered nurse who has completed a supplemental educational curriculum.
The GCPFF melds support for family caregivers with the delivery of coordinated and comprehensive chronic care and seeks to improve the health and well-being of both patients and their family caregivers. The GCPFF encompasses (a) an initial meeting between the nurse and the patient's primary caregiver, (b) education and referral to community resources, (c) ongoing “coaching,” (d) a six-session group Caregiver Workshop, and (e) monthly Support Group meetings, all facilitated by the patient's GC nurse.
A cluster-randomized controlled trial of GC is underway in 14 primary care physician teams. Of 904 consented patients, 450 (49.8%) identified a primary caregiver; 308 caregivers met eligibility criteria, consented to participate, and completed a baseline interview. At 6-month follow-up, intervention group caregivers’ mean Center for Epidemiological Studies Depression (CESD) and Caregiver Strain Index (CSI) scores were respectively 0.97 points (p = .14) and 1.14 points (p = .06) lower than control group caregivers’. Among caregivers who provided more than 14 hours of weekly assistance at baseline, intervention group caregivers’ mean CESD and CSI scores were respectively 1.23 points (p = .20) and 1.83 points (p = .04) lower than control group caregivers’.
The GCPFF may benefit family caregivers of chronically ill older adults. Outcomes will continue to be monitored at 18-months follow-up.
Caregiving; Chronic disease; Nursing; Primary care
We focus on estimation of the causal effect of treatment on the functional status of individuals at a fixed point in time t* after they have experienced a catastrophic event, from observational data with the following features: (1) treatment is imposed shortly after the event and is non-randomized, (2) individuals who survive to t* are scheduled to be interviewed, (3) there is interview non-response, (4) individuals who die prior to t* are missing information on pre-event confounders, (5) medical records are abstracted on all individuals to obtain information on post-event, pre-treatment confounding factors. To address the issue of survivor bias, we seek to estimate the survivor average causal effect (SACE), the effect of treatment on functional status among the cohort of individuals who would survive to t* regardless of whether or not assigned to treatment. To estimate this effect from observational data, we need to impose untestable assumptions, which depend on the collection of all confounding factors. Since pre-event information is missing on those who die prior to t*, it is unlikely that these data are missing at random (MAR). We introduce a sensitivity analysis methodology to evaluate the robustness of SACE inferences to deviations from the MAR assumption. We apply our methodology to the evaluation of the effect of trauma center care on vitality outcomes using data from the National Study on Costs and Outcomes of Trauma Care.
We consider the problem of comparing cumulative incidence functions of non-mortality events in the presence of informative coarsening and the competing risk of death. We extend frequentist-based hypothesis tests previously developed for non-informative coarsening and propose a novel Bayesian method based on comparing a posterior parameter transformation to its expected distribution under the null hypothesis of equal cumulative incidence functions. Both methods use estimates derived by extending previously published estimation procedures to accommodate censoring by death. The data structure and analysis goal are exemplified by the AIDS Link to the Intravenous Experience (ALIVE) study, where researchers are interested in comparing incidence of human immunodeficiency virus seroconversion by risk behavior categories. Coarsening in the forms of interval and right censoring and censoring by death in ALIVE are thought to be informative, thus we perform a sensitivity analysis by incorporating elicited expert information about the relationship between seroconversion and censoring into the model.
Bayesian Analysis; Frequentist Analysis; Hypothesis Test; Interval Censoring; Markov Chain Monte Carlo; Sensitivity Analysis
In this paper, the authors use the rubric of “coarsened data,” of which missing and censored data are special cases, to motivate the elicitation and use of expert information for performing sensitivity analyses of censored event-time data. Elicited information is important because observed data are insufficient to estimate how study participants with coarsened data compare with participants with uncoarsened data, and misspecifying this comparison may produce biased analysis results. In the presence of coarsening, performing a sensitivity analysis over a range of plausible assumptions is the best one can do. Here the authors illustrate an approach for eliciting expert information for use in sensitivity analyses to compare cumulative incidence functions of censored nonmortality outcomes. An example of such data is the AIDS Link to Intravenous Experience (ALIVE) Study, where the authors aim to estimate and compare cumulative incidence functions for human immunodeficiency virus between risk factor categories. The interval and right-censoring and censoring due to death found in the ALIVE data (1988–1998) are thought to be informative; thus, a sensitivity analysis is performed using information elicited from 2 ALIVE scientists and an expert in acquired immunodeficiency syndrome epidemiology about the relation between seroconversion and censoring.
Bayesian analysis; frequentist approach; HIV; hypothesis test; incidence; interval censoring; sensitivity analysis
Using validation sets for outcomes can greatly improve the estimation of vaccine efficacy (VE) in the field (Halloran and Longini, 2001; Halloran and others, 2003). Most statistical methods for using validation sets rely on the assumption that outcomes on those with no cultures are missing at random (MAR). However, often the validation sets will not be chosen at random. For example, confirmational cultures are often done on people with influenza-like illness as part of routine influenza surveillance. VE estimates based on such non-MAR validation sets could be biased. Here we propose frequentist and Bayesian approaches for estimating VE in the presence of validation bias. Our work builds on the ideas of Rotnitzky and others (1998, 2001), Scharfstein and others (1999, 2003), and Robins and others (2000). Our methods require expert opinion about the nature of the validation selection bias. In a re-analysis of an influenza vaccine study, we found, using the beliefs of a flu expert, that within any plausible range of selection bias the VE estimate based on the validation sets is much higher than the point estimate using just the non-specific case definition. Our approach is generally applicable to studies with missing binary outcomes with categorical covariates.
Bayesian; Expert opinion; Identifiability; Influenza; Missing data; Selection model; Vaccine efficacy
In randomized studies with missing outcomes, non-identifiable assumptions are required to hold for valid data analysis. As a result, statisticians have been advocating the use of sensitivity analysis to evaluate the effect of varying asssumptions on study conclusions. While this approach may be useful in assessing the sensitivity of treatment comparisons to missing data assumptions, it may be dissatisfying to some researchers/decision makers because a single summary is not provided. In this paper, we present a fully Bayesian methodology that allows the investigator to draw a ‘single’ conclusion by formally incorporating prior beliefs about non-identifiable, yet interpretable, selection bias parameters. Our Bayesian model provides robustness to prior specification of the distributional form of the continuous outcomes.
Dirichlet process prior; Identifiability; MCHC; Non-parametric Bayes; Selection model; Sensitivity analysis
The etiology of bacterial vaginosis is unknown, and there are no long-term therapies for preventing this frequently recurring condition. Vaginal douching has been reported to be associated with bacterial vaginosis in observational studies. However, this association may be due to confounding by indication—that is, confounding by women douching in response to vaginal symptoms associated with bacterial vaginosis. The authors used marginal structural modeling to estimate the causal effect of douching on bacterial vaginosis risk while controlling for this confounding effect. In 1999–2002, nonpregnant women (n = 3,620) were recruited into a prospective study when they visited one of 12 public health clinics in Birmingham, Alabama, for routine care. Participants were assessed quarterly for 1 year. Bacterial vaginosis was based on a Nugent's Gram stain score of 7 or higher. Thirty-two percent of participants douched in every study interval, and 43.0% never douched. Of the 12,349 study visits, 40.2% were classified as involving bacterial vaginosis. The relative risk for regular douching as compared with no douching was 1.21 (95% confidence interval: 1.08, 1.38). These findings indicate that douching confers increased risk of disruption of vaginal flora. In the absence of a large randomized trial, these findings provide the best evidence to date for a risk of bacterial vaginosis associated with douching.
confounding factors (epidemiology); epidemiologic methods; longitudinal studies; models, structural; vaginal douching; vaginosis, bacterial
To evaluate the risk for bacterial vaginosis (BV) in a douching cessation trial.
Thirty-nine reproductive-age women who reported use of douche products were enrolled into a 20-week study consisting of a 4-week douching observation (phase I) followed by 12-weeks of douching cessation (phase II). In phase III, participants then chose to resume douching or continue cessation for the remaining 4 weeks. Self-collected vaginal samples were obtained twice-weekly in the first 16 weeks and one sample was collected during week 20 (1,107 samples total). BV was diagnosed by Nugent score ≥7. Conditional logistic regression was used to evaluate douching cessation on the risk of BV.
The adjusted odds ratio (aOR) for BV in the douching cessation phase as compared to the douching observation phase was 0.76 (95% CI:0.33–1.76). Among women who reported their primary reason for douching was to cleanse after menstruation, BV was significantly reduced in douching cessation (aOR:0.23; 95% CI:0.12–0.44).
Vaginal douching cessation may reduce the risk for BV in a subset of women.
vaginal douching; bacterial vaginosis; intravaginal cleansing; intravaginal washing
The etiology of bacterial vaginosis (BV) is unknown and there are no long-term therapies for preventing this frequently recurring condition. Vaginal douching has been reported to be associated with BV in observational studies. However, this association may be due to confounding by indication-- women douching in response to vaginal symptoms associated with BV. Marginal structural modeling was used to estimate the causal effect of douching on risk for BV controlling for this confounding effect. From 1999-2002, non-pregnant women (n=3620) were recruited into a prospective study when presenting for routine care at 12 public health clinics in Birmingham, Alabama. Participants were assessed quarterly for one year. BV was based on Nugent’s Gram stain score ≥ 7. Thirty-two percent of participants douched in every interval and 43.0% never douched. Of the 12,349 visits, 40.2% were classified as having BV. The relative risk for regular douching practice compared with no douching practice was 1.21 (95% CI: 1.08, 1.38). Our findings indicate that douching confers an increased risk for disruption of vaginal flora. In the absence of a large randomized trial, these findings provide the best evidence to date for the risk of douching on BV.
Vaginosis, Bacterial; Vaginal Douching; epidemiologic methods; Longitudinal Studies; Models, Structural; Confounding Factor; Epidemiologic; time-dependent confounding
The short-term mortality benefit of lower tidal volume ventilation (LTVV) for patients with acute lung injury/acute respiratory distress syndrome (ALI/ARDS) has been demonstrated in a large, multi-center randomized trial. However, the impact of LTVV and other critical care therapies on the longer-term outcomes of ALI/ARDS survivors remains uncertain. The Improving Care of ALI Patients (ICAP) study is a multi-site, prospective cohort study that aims to evaluate the longer-term outcomes of ALI/ARDS survivors with a particular focus on the effect of LTVV and other critical care therapies.
Consecutive mechanically ventilated ALI/ARDS patients from 11 intensive care units (ICUs) at four hospitals in the city of Baltimore, MD, USA, will be enrolled in a prospective cohort study. Exposures (patient-based, clinical management, and ICU organizational) will be comprehensively collected both at baseline and throughout patients' ICU stay. Outcomes, including mortality, organ impairment, functional status, and quality of life, will be assessed with the use of standardized surveys and testing at 3, 6, 12, and 24 months after ALI/ARDS diagnosis. A multi-faceted retention strategy will be used to minimize participant loss to follow-up.
On the basis of the historical incidence of ALI/ARDS at the study sites, we expect to enroll 520 patients over two years. This projected sample size is more than double that of any published study of long-term outcomes in ALI/ARDS survivors, providing 86% power to detect a relative mortality hazard of 0.70 in patients receiving higher versus lower exposure to LTVV. The projected sample size also provides sufficient power to evaluate the association between a variety of other exposure and outcome variables, including quality of life.
The ICAP study is a novel, prospective cohort study that will build on previous critical care research to improve our understanding of the longer-term impact of ALI/ARDS, LTVV and other aspects of critical care management. Given the paucity of information about the impact of interventions on long-term outcomes for survivors of critical illness, this study can provide important information to inform clinical practice.
Difficulties with providing quality primary health care for low-income Americans have been well documented. Few studies have addressed the challenges faced by pediatric clinicians serving low-income families or whether practice-based interventions improve clinicians’ ability to provide quality preventive health services. We investigated if, over time, the Healthy Steps for Young Children program affected the practices and perceptions of clinicians in pediatric primary care practices serving low-income families compared to practices serving more affluent families. Self-administered questionnaires were completed at baseline (N=104) and at 30 months (N=91) by clinicians at 20 pediatric practices participating in the Healthy Steps program. Practices were divided into three groups: those serving families with low, middle, and high incomes. Barriers to providing care, provision of preventive developmental services, and perceptions of care were assessed at baseline and at 30 months after introducing the program. Across all income groups and over time, clinicians were more likely to report the provision of preventive developmental health services. Clinicians in low-income practices reported increased problems with both reimbursement and time barriers; clinicians in high-income practices reported increased problems with reim-bursement. At 30 months, clinicians serving low-income families reported the greatest positive changes in their perceptions about the quality of care provided by their practices. They also were more likely to strongly agree that they gave support to families and to be very satisfied with the ability of their clinical staff to meet the developmental needs of children. We found that Healthy Steps was successful in universally increasing developmental services despite the reported practice barriers for both low- and high-income practices. The Healthy Steps program enabled low-income practices to achieve similar levels of clinician satisfaction as middle- and high-income practices despite having reported lower levels at the beginning months of the program.
Child development; Low-income population; Preventive health services; Pediatrics; Staff attitudes