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INTRODUCTION: Tobacco smoke exposure (TSE) harms children and adults. Studies of childhood TSE exposure often relies on parental reports, but may benefit from objective measures. The objective of our study was to study the relationship between reported and objective measures of TSE. METHODS: We analyzed data from four intervention trials, conducted in clinical or community settings, to identify objective measures most closely associated with parent-reported measures and the optimal set of parent-reported measures for predicting objective measures. We also assessed whether there was a learning curve in reported exposure over time, and the importance of replicate biomarker measures. RESULTS: Correlations between objective and parent-reported measures of child TSE were modest at best, ranging from zero to 0.41. Serum cotinine and urinary cotinine were most strongly associated with parental reports. Parental questions most closely related to biomarkers were number of cigarettes and home smoking rules; together these formed the best set of predictive questions. No trial included all objective measures and all questions, precluding definitive statements about relative advantages. Within-subject repeatability of biomarker measures varied across studies, suggesting that direct pilot data are needed to assess the benefit of replicate measurements. CONCLUSIONS: Improvements in objective and parent-reported child exposure measurements are needed to accurately monitor child TSE, evaluate efforts to reduce such exposure, and better protect child health.

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BACKGROUND: The Asthma Impact on Quality of Life Scale (A-IQOLS) assesses the patient-perceived negative effect of asthma on quality of life. Its standard error of measurement is known; it has strong construct, convergent, and divergent validity; and it provides information that is unique among asthma outcome measures. OBJECTIVE: We sought to characterize the psychometric properties of the A-IQOLS and its suitability for use in demographically and clinically diverse adult asthmatic populations. METHODS: Data from participants in 5 independent asthma studies, with samples ranging from patients with well-controlled moderate asthma to patients with severe poorly controlled asthma, were pooled to determine the psychometric performance of A-IQOLS scores overall and in multiple demographic, disease status, and study subgroups. RESULTS: Pooled sample (n = 597) age averaged 45 years; 66% were female, 65% were white, 22% were African American, 11% were Hispanic, and 11% had a high school education or less. The rated importance of its underlying life dimensions and associations between A-IQOLS scores and lung function, symptom, Asthma Control Test, Juniper Mini Asthma Quality of Life Questionnaire, and Marks Asthma Quality of Life Questionnaire scores was very similar, regardless of patients' demographic and clinical characteristics. A-IQOLS scores discriminated among the individual study samples, as well as other patient-reported symptom and functional status measures. Distribution and anchor-based considerations suggest an A-IQOLS minimum clinically important difference in the vicinity of 0.50 and not less than 0.33 scale score units. CONCLUSIONS: A-IQOLS is valid for research and potentially clinical use in demographically and clinically diverse patients.

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BACKGROUND: The Asthma Impact on Quality of Life Scale (A-IQOLS) assesses the negative effect of asthma on quality of life (QoL) from the patient's perspective by using dimensions of Flanagan's Quality of Life Scale (QOLS), a measure of current QoL. OBJECTIVES: We sought to determine and compare the psychometric properties of the A-IQOLS and QOLS, including their sensitivities to differences and change in asthma status. METHODS: In a test-retest design (3- to 5-week interval) adults with persistent asthma underwent spirometry and were administered the A-IQOLS, other asthma outcome measures (Asthma Control Test, Asthma Symptom Utility Index, and the Marks and Juniper Asthma Quality of Life Questionnaires), and the QOLS. RESULTS: Participants' (n = 147) mean age was 49 years, 76% were white, 12% were Hispanic, and 65% were female. A-IQOLS and QOLS scores were significantly correlated with other asthma outcomes scores, except FEV1, but shared relatively low common variance with these measures. A-IQOLS but not QOLS score changes were significantly correlated with changes in asthma outcomes. An A-IQOLS standard error of measurement of 0.27 implies that a within-person score change of ±0.73 or greater constitutes a true change. The QOLS standard error of measurement was 0.43. CONCLUSIONS: A-IQOLS provides a reliable, valid, and unique assessment of the patient-perceived negative effect of asthma on QoL that is suitable for use in asthma clinical research and potentially in clinical care. Further studies are needed in diverse patient populations. QOLS, a measure of current QoL, is less sensitive to disease status changes but might be useful in characterizing study populations, in treatment adherence research, and as a clinical and research tool in patients with multiple, severe, and/or life-limiting chronic conditions.

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Rigorous research on the benefit of healthy eating patterns for asthma control is lacking.We randomised 90 adults with objectively confirmed uncontrolled asthma and a low-quality diet (Dietary Approaches to Stop Hypertension (DASH) scores <6 out of 9) to a 6-month DASH behavioural intervention (n=46) or usual-care control (n=44). Intention-to-treat analyses used repeated-measures mixed models.Participants were middle-aged, 67% female and multiethnic. Compared with controls, intervention participants improved on DASH scores (mean change (95% CI) 0.6 (0, 1.1) versus -0.3 (-0.8, 0.2); difference 0.8 (0.2, 1.5)) and the primary outcome, Asthma Control Questionnaire scores (-0.2 (-0.5, 0) versus 0 (-0.3, 0.3); difference -0.2 (-0.5, 0.1)) at 6 months. The mean group differences in changes in Mini Asthma Quality of Life Questionnaire overall and subdomain scores consistently favoured the intervention over the control group: overall 0.4 (95% CI 0, 0.8), symptoms 0.5 (0, 0.9), environment 0.4 (-0.1, 1.0), emotions 0.4 (-0.2, 0.9) and activities 0.3 (0, 0.7). These differences were modest, but potentially clinical significant.The DASH behavioural intervention improved diet quality with promising clinical benefits for better asthma control and functional status among adults with uncontrolled asthma. A full-scale efficacy trial is warranted.

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OBJECTIVE: 'DASH for Asthma' (n 90) was a 6-month randomized controlled trial that demonstrated potential benefits of a DASH (Dietary Approaches to Stop Hypertension) behavioural intervention for improving diet quality and asthma control by comparing intervention to usual care in adults with uncontrolled asthma. The present study examined acceptability and feasibility of the intervention from the perspective of intervention participants and lifestyle coaches. DESIGN: Grounded in Social Cognitive Theory, the 3-month intensive stage, including three individual and eight group sessions, focused on diet modifications and behavioural self-regulation. The 3-month maintenance stage contained telephone consultations. Participants and lifestyle coaches completed surveys including 5-point Likert scales and open-ended questions. We analysed data using descriptive and inductive content analyses. SUBJECTS: Forty-six intervention participants (survey response rate was 65-72 %) and two lifestyle coaches. RESULTS: Participants and lifestyle coaches were highly satisfied (all mean ratings >4) with individual and group sessions. Participants identified mastery of knowledge and skills (awareness, goal setting, self-monitoring, problem solving), social learning (class members sharing experiences and ideas) and good coaching skills (reflective listening, empathy, motivational counselling) as important contributors to self-efficacy and programme satisfaction. Participants also valued personalized feedback received in individual sessions. Lifestyle coaches viewed participant engagement as a facilitator to effective sessions. Finally, participants and lifestyle coaches identified food tasting as beneficial for observational learning and facilitation of participant engagement. High class attendance and self-monitoring rate also reflected the high engagement among participants. CONCLUSIONS: The DASH behavioural intervention was feasible and highly acceptable to participants with uncontrolled asthma and lifestyle coaches.

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To advance implementation research (IR) in respiratory, sleep, and critical care medicine, the American Thoracic Society and the Division of Lung Diseases from the NHLBI cosponsored an Implementation Research Workshop on May 17, 2014. The goals of IR are to understand the barriers and facilitators of integrating new evidence into healthcare practices and to develop and test strategies that systematically target these factors to accelerate the adoption of evidence-based care. Throughout the workshop, presenters provided examples of IR that focused on the rate of adoption of evidence-based practices, the feasibility and acceptability of interventions to patients and other stakeholders who make healthcare decisions, the fidelity with which practitioners use specific interventions, the effects of specific barriers on the sustainability of an intervention, and the implications of their research to inform policies to improve patients' access to high-quality care. During the discussions that ensued, investigators' experience led to recommendations underscoring the importance of identifying and involving key stakeholders throughout the research process, ensuring that those who serve as reviewers understand the tenets of IR, managing staff motivation and turnover, and tackling the challenges of scaling up interventions across multiple settings.

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RATIONALE: The effect of weight loss on asthma in obese adults warrants rigorous investigation. OBJECTIVES: To examine an evidence-based, practical, and comprehensive lifestyle intervention targeting modest weight loss and increased physical activity for asthma control. METHODS: The trial randomized 330 obese adults with uncontrolled asthma to receive usual care enhanced with a pedometer, a weight scale, information about existing weight management services at the participating clinics, and an asthma education DVD, or with these tools plus the 12-month intervention. MEASUREMENTS AND MAIN RESULTS: The primary outcome was change in Asthma Control Questionnaire (ACQ) scores from baseline to 12 months. Participants (mean [SD] age, 47.6 [12.4] yr) were 70.6% women, 20.0% non-Hispanic black, 20.3% Hispanic/Latino, and 8.2% Asian/Pacific Islander. At baseline, they were obese (mean [SD] body mass index, 37.5 [5.9] kg/m(2)) and had uncontrolled asthma (Asthma Control Test score, 15.1 [3.8]). Compared with control subjects, intervention participants achieved significantly greater mean weight loss (±SE) (intervention, -4.0 ± 0.8 kg vs. control, -2.1 ± 0.8 kg; P = 0.01) and increased leisure-time activity (intervention, 418.2 ± 110.6 metabolic equivalent task-min/wk vs. control, 178.8 ± 109.1 metabolic equivalent task-min/wk; P = 0.05) at 12 months. But between-treatment mean (±SE) differences were not significant for ACQ changes (intervention, -0.3 ± 0.1 vs. control, -0.2 ± 0.1; P = 0.92) from baseline (mean [SD], 1.4 [0.8]), nor for any other clinical asthma outcomes (e.g., spirometric results and asthma exacerbations). Among all participants regardless of treatment assignment, weight loss of 10% or greater was associated with a Cohen d effect of 0.76 and with 3.78 (95% confidence interval, 1.72-8.31) times the odds of achieving clinically significant reductions (i.e., ≥0.5) on ACQ as stable weight (<3% loss or gain from baseline). The effects of other weight change categories were small. CONCLUSIONS: Moderately and severely obese adults with uncontrolled asthma can safely participate in evidence-based lifestyle intervention for weight loss and active living. The modest average weight and activity improvements are comparable to those shown to reduce cardiometabolic risk factors in studies of similar interventions in other populations but are not associated with significant net benefits for asthma control or other clinical asthma outcomes in the current population. Instead, weight loss of 10% or greater may be required to produce clinically meaningful improvement in asthma. Clinical trial registered with www.clinicaltrials.gov (NCT00901095).

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RATIONALE: Abdominal adiposity may be an important risk factor for uncontrolled asthma in adults, controlling for general obesity. Whether the relationship, if present, is explained by other factors (e.g., asthma onset age, sex, and/or coexisting conditions) is unclear. OBJECTIVES: To examine whether clinically applicable anthropometric measures of abdominal adiposity--waist circumference and waist-to-height ratio (WHtR)--are related to poorer asthma control in adults with uncontrolled asthma controlling for body mass index (BMI), and whether the relationship (if present) is explained by gastroesophageal reflux disorder (GERD), sleep quality, or obstructive sleep apnea (OSA) or differs by age of asthma onset or sex. METHODS: Patients aged 18 to 70 years with uncontrolled asthma (n = 90) participated in a 6-month randomized clinical trial. MEASUREMENTS AND MAIN RESULTS: Baseline measures included sociodemographics, standardized anthropometrics, Asthma Control Test (ACT), GERD Symptom Assessment Scale, Pittsburgh Sleep Quality Index, and Berlin Questionnaire for Sleep Apnea. Participants (mean [SD] age, 52 [12] yr) were racially and ethnically diverse, 67% women, and 69% overweight or obese, and 71% reported their age of asthma onset was 12 years or older. Participants had uncontrolled asthma (mean [SD] ACT score, 14.9 [3.7]) and low GERD symptoms score (0.6 [0.4]); 67% reported poor sleep quality, and 42% had a high OSA risk. General linear regression results showed that worse ACT scores were significantly associated with every SD increase in waist circumference (ß = -1.03; 95% confidence interval [CI], -1.96 to -0.16; P = 0.02) and waist-to-height ratio (ß = -1.16; 95% CI, -2.00 to -0.33; P = 0.008), controlling for sociodemographics. Waist-to-height ratio remained correlated with ACT (ß = -2.30; 95% CI, -4.16 to -0.45; P = 0.02) after further adjusting for BMI. The BMI-controlled relationship between WHtR and ACT did not differ by age of asthma onset or sex (P > 0.05 for interactions) and persisted after additional adjustment for GERD, sleep quality, or OSA scores. Poor sleep quality was associated with worse ACT scores (ß = -0.87; 95% CI, -1.71 to -0.03; P = 0.045) controlling for waist-to-height ratio, BMI, and sociodemographics. CONCLUSIONS: Abdominal adiposity by waist-to-height ratio and poor sleep quality correlated with poorer asthma control in adults with uncontrolled asthma, after controlling for BMI and sociodemographics. These results warrant replication in larger studies of diverse populations. Clinical trial registered with www.clinicaltrials.gov (NCT 01725945).

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PURPOSE OF REVIEW: Shared decision-making (SDM) is an emerging field that promises to improve healthcare. We aim to explore the concept of SDM, how it has been studied or applied in the treatment of asthma, and how it might be implemented to improve adherence and outcomes in pediatric asthma. RECENT FINDINGS: Healthcare providers often fail to involve their patients in clinical decision-making by not presenting all available options, associated risks and benefits, in light of the patient's values, preferences, concerns, lifestyle, and perceived barriers to following various treatment regimens. It has been argued that SDM is preferable to a clinician-controlled approach and may improve patient outcomes (increase satisfaction with care, reduce decisional conflict and decisional regret, improve health-related quality of life, and increase decision-specific knowledge). This may be especially important in managing chronic conditions in which adherence to treatment regimen may increase if the patient was actively involved in the decision-making. In pediatrics, the decision process is further complicated by the clinician-parent(s)-child interaction. We found no studies on how to effectively involve and communicate with children at different developmental levels, or how to coalesce the parent and child's perspective to work as a unit. SUMMARY: SDM has the promise to improve satisfaction with disease management, treatment adherence and patient-centered outcomes in pediatric asthma, but further research is needed to determine its effectiveness and to establish guidelines on how to implement SDM in the clinical setting and incorporate the input and preferences of all stakeholders' perspectives.

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OBJECTIVE: To examine weight loss patterns and predictors among participants in a primary care-based translation study of the Diabetes Prevention Program lifestyle intervention. DESIGN AND METHODS: Cluster analysis identified short-term (12-week) weight loss patterns among 72 intervention participants. Analysis of variance assessed cluster differences in weight loss maintenance at 15-month follow-up. Discriminant analysis identified baseline characteristics that best differentiated between clusters. RESULTS: Participants had baseline mean (SD) age of 55.0 (10.8) years and BMI of 31.9 (5.2) kg/m(2) . Cluster analysis identified three short-term weight loss patterns: modest (n = 15; 21%), moderate-and-steady (n = 43; 60%), and substantial-and-early (n = 14; 19%). Only participants with the latter two patterns achieved clinically significant (≥5%) short-term weight loss and maintained it at 15 months. On discriminant analysis, the modest cluster was most differentiated from other clusters by high friend encouragement for dietary change, high obesity-related problems, and low physical well-being. The moderate-and-steady cluster was differentiated by lower physical activity, family encouragement, and depression symptoms. CONCLUSION: Results provided insight into the heterogeneity of response to an effective lifestyle intervention by identifying short-term weight loss patterns and their baseline predictors and relationship to 15-month success. If replicated, results may help tailor strategies for participant subgroups in weight loss programs.

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BACKGROUND: Alcohol consumption and its interaction with disease, medication use, and functional status may result in serious health problems, but little information exists about the national prevalence of alcohol-related health risk in older adults. OBJECTIVE: To estimate the prevalence of harmful and hazardous alcohol use and the prevalence of consumption in excess of National Institute of Alcohol Abuse and Alcoholism (NIAAA) recommendations, in people aged 65 and older, and by sex and race/ethnicity sub-group. DESIGN: Cross-sectional, using data from the 2005-2008 National Health and Nutrition Examination Survey of the non-institutionalized U.S. population. PARTICIPANTS: One thousand and eighty-three respondents aged 65 and older who consume alcohol. MAIN MEASURES: Participants' alcohol consumption was classified as Harmful, Hazardous, or Healthwise, in the context of their specific health status, using the Alcohol-Related Problems Survey classification algorithm. KEY RESULTS: Overall, 14.5 % of older drinkers (95 % CI: 12.1 %, 16.8 %) consumed alcohol above the NIAAA's recommended limits. However, when health status was taken into account, 37.4 % of older drinkers (95 % CI: 34.9 %, 40.0 %) had Harmful consumption and 53.3 % (95 % CI: 50.1 %, 56.6 %) had either Hazardous or Harmful consumption. Among light/moderate drinkers, the proportions were 17.7 % (95 % CI: 14.7 %, 20.7 %) and 28.0 % (95 % CI: 24.8 %, 31.1 %), respectively. Male drinkers had significantly greater odds of Hazardous/Harmful consumption than female drinkers (OR = 2.14 [95 % CI: 1.77, 2.6]). Black drinkers had worse health status and significantly greater odds of Hazardous/Harmful consumption than white drinkers (OR = 1.49; 95 % CI: 1.02, 2.17), despite having no greater prevalence of drinking in excess of NIAAA-recommended limits. CONCLUSION: Most older Americans who drink are light/moderate drinkers, yet substantial proportions of such drinkers drink in a manner that is either harmful or hazardous to their health. Older adults with risky alcohol consumption are unlikely to be identified by health care providers if clinicians rely solely on whether patient consumption exceeds the NIAAA-recommended limits.

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This pilot study aims to provide effect size confidence intervals, clinical trial and intervention feasibility data, and procedural materials for a full-scale randomized controlled trial that will determine the efficacy of Dietary Approaches to Stop Hypertension (DASH) as adjunct therapy to standard care for adults with uncontrolled asthma. The DASH diet encompasses foods (e.g., fresh fruit, vegetables, and nuts) and antioxidant nutrients (e.g., vitamins A, C, E, and zinc) with potential benefits for persons with asthma, but it is unknown whether the whole diet is beneficial. Participants (n = 90) will be randomized to receive usual care alone or combined with a DASH intervention consisting of 8 group and 3 individual sessions during the first 3 months, followed by at least monthly phone consultations for another 3 months. Follow-up assessments will occur at 3 and 6 months. The primary outcome measure is the 7-item Juniper Asthma Control Questionnaire, a validated composite measure of daytime and nocturnal symptoms, activity limitations, rescue medication use, and percentage predicted forced expiratory volume in 1 second. We will explore changes in inflammatory markers important to asthma pathophysiology (e.g., fractional exhaled nitric oxide) and their potential to mediate the intervention effect on disease control. We will also conduct pre-specified subgroup analyses by genotype (e.g., polymorphisms on the glutathione S transferase gene) and phenotype (e.g., atopy, obesity). By evaluating a dietary pattern approach to improving asthma control, this study could advance the evidence base for refining clinical guidelines and public health recommendations regarding the role of dietary modifications in asthma management.

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The E-LITE (Evaluation of Lifestyle Interventions to Treat Elevated Cardiometabolic Risk in Primary Care) trial evaluated the feasibility and potential effectiveness of translating an evidence-based lifestyle intervention for the management of obesity and related risk factors in a primary care setting. Delivered by allied health care providers, the intervention promoted at least 7% weight loss and at least 150 minutes per week of moderate-intensity physical activity through gradual, sustainable lifestyle changes. Activities included interactive group lessons, food tasting, guided physical activity, and technology-mediated self-monitoring and behavioral counseling. This article discusses insights and potential areas for improvement to strengthen program implementation for dissemination of the E-LITE program to other primary care settings. We focus on (a) the role of allied health professionals in program delivery, (b) strengthening program integration within a primary care clinic, and (c) the use of information technology to extend the reach and impact of the program. Our experience shows the feasibility of implementing an evidence-based lifestyle intervention program combining group-delivered nutrition and behavioral counseling, physical activity training, and technology-mediated follow-up in a primary care setting. Challenges remain, and we offer possible solutions to overcome them.

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BACKGROUND: The Diabetes Prevention Program (DPP) lifestyle intervention reduced the incidence of type 2 diabetes mellitus (DM) among high-risk adults by 58%, with weight loss as the dominant predictor. However, it has not been adequately translated into primary care. METHODS: We evaluated 2 adapted DPP lifestyle interventions among overweight or obese adults who were recruited from 1 primary care clinic and had pre-DM and/or metabolic syndrome. Participants were randomized to (1) a coach-led group intervention (n = 79), (2) a self-directed DVD intervention (n = 81), or (3) usual care (n = 81). During a 3-month intensive intervention phase, the DPP-based behavioral weight-loss curriculum was delivered by lifestyle coach-led small groups or home-based DVD. During the maintenance phase, participants in both interventions received lifestyle change coaching and support remotely-through secure email within an electronic health record system and the American Heart Association Heart360 website for weight and physical activity goal setting and self-monitoring. The primary outcome was change in body mass index (BMI) (calculated as weight in kilograms divided by height in meters squared) from baseline to 15 months. RESULTS: At baseline, participants had a mean (SD) age of 52.9 (10.6) years and a mean BMI of 32.0 (5.4); 47% were female; 78%, non-Hispanic white; and 17%, Asian/Pacific Islander. At month 15, the mean ± SE change in BMI from baseline was -2.2 ± 0.3 in the coach-led group vs -0.9 ± 0.3 in the usual care group (P < .001) and -1.6 ± 0.3 in the self-directed group vs usual care (P = .02). The percentages of participants who achieved the 7% DPP-based weight-loss goal were 37.0% (P = .003) and 35.9% (P = .004) in the coach-led and self-directed groups, respectively, vs 14.4% in the usual care group. Both interventions also achieved greater net improvements in waist circumference and fasting plasma glucose level. CONCLUSION: Proven effective in a primary care setting, the 2 DPP-based lifestyle interventions are readily scalable and exportable with potential for substantial clinical and public health impact. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00842426.

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BACKGROUND: Patient adherence, the level of asthma self-management skills, exposure to stress, and depression can have considerable influence on a wide range of asthma outcomes and thus are considered asthma outcome mediators. OBJECTIVE: National Institutes of Health institutes and other federal agencies convened an expert group to recommend standardized measures for 7 domains of asthma clinical research outcomes measures. Although the review of mediators of these outcomes was not within the scope of any specific outcome topic, a brief summary is presented so that researchers might consider potential mediators. METHODS: We prepared a summary of key mediators of asthma outcomes based on expertise and knowledge of the literature. RESULTS: The rationale for including measures of adherence, self-management skills, and exposures to stress in asthma clinical research is presented, along with a brief review of instruments for collecting this information from clinical research participants. CONCLUSIONS: Appropriate measurement of adherence, self-management skills, and exposures to stress will enhance characterization of study participants and provide information about the potential impact these factors can have on mediating the effects of treatment interventions.

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BACKGROUND: "Asthma-related quality of life" (QOL) refers to the perceived impact that asthma has on the patient's QOL. OBJECTIVE: National Institutes of Health institutes and other federal agencies convened an expert group to recommend standardized measures of the impact of asthma on QOL for use in future asthma clinical research. METHODS: We reviewed published documentation regarding the development and psychometric evaluation; clinical research use since 2000; and extent to which the content of each existing QOL instrument provides a unique, reliable, and valid assessment of the intended construct. We classified instruments as core (required in future studies), supplemental (used according to the study's aims and standardized), or emerging (requiring validation and standardization). This work was discussed at an National Institutes of Health-organized workshop convened in March 2010 and finalized in September 2011. RESULTS: Eleven instruments for adults and 6 for children were identified for review. None qualified as core instruments because they predominantly measured indicators of asthma control (symptoms and/or functional status); failed to provide a distinct, reliable score measuring all key dimensions of the intended construct; and/or lacked adequate psychometric data. CONCLUSIONS: In the absence of existing instruments that meet the stated criteria, currently available instruments are classified as either supplemental or emerging. Research is strongly recommended to develop and evaluate instruments that provide a distinct, reliable measure of the patient's perception of the impact of asthma on all of the key dimensions of QOL, an important outcome that is not captured in other outcome measures.

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Asthma in the elderly is underdiagnosed and undertreated, and there is a paucity of knowledge on the subject. The National Institute on Aging convened this workshop to identify what is known and what gaps in knowledge remain and suggest research directions needed to improve the understanding and care of asthma in the elderly. Asthma presenting at an advanced age often has similar clinical and physiologic consequences as seen with younger patients, but comorbid illnesses and the psychosocial effects of aging might affect the diagnosis, clinical presentation, and care of asthma in this population. At least 2 phenotypes exist among elderly patients with asthma; those with longstanding asthma have more severe airflow limitation and less complete reversibility than those with late-onset asthma. Many challenges exist in the recognition and treatment of asthma in the elderly. Furthermore, the pathophysiologic mechanisms of asthma in the elderly are likely to be different from those seen in young asthmatic patients, and these differences might influence the clinical course and outcomes of asthma in this population.

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BACKGROUND: Minimizing the imbalance of key baseline covariates between treatments is known to be very important to the precision of the estimate of treatment effect in clinical research. Dynamic randomization allocation techniques have been used to achieve balance across multiple baseline characteristics. However, empirical data are limited on how these techniques compare in terms of balance and efficiency. We are motivated by a newly funded randomized controlled trial, in which we have the option of choosing between two methods of randomization at the subject level: (1) randomizing individual subjects consecutively as they are enrolled, using Pocock and Simon's minimization method, and (2) simultaneously randomizing blocks of subjects once all subjects in a block have been enrolled, using a balance algorithm originally developed for cluster randomized trials. PURPOSE: To compare dynamic block randomization and minimization in terms of balance on baseline covariates and statistical efficiency. Simple randomization was included as a reference. METHODS: A simulation study using data from a previous randomized controlled trial was conducted to compare balance statistics and the accuracy and power of hypothesis testing among the randomization methods. RESULTS: Dynamic block randomization consistently produced the best balance and highest power for various sample and treatment effect sizes, even after post-adjustment of the pre-specified baseline covariates in all three methods. Consistent with previous reports, minimization performed better in balance and power than simple randomization; however, the differences were noticeably smaller compared to those between dynamic block randomization and simple randomization. LIMITATIONS: In this simulation study, we considered three sample sizes and two block sizes for a two-arm randomized trial. We assumed no interactions among the multiple baseline covariates. It is necessary to evaluate how the results may vary when the simulation conditions are changed before drawing broader conclusions regarding comparisons between the randomization methods. CONCLUSIONS: This study demonstrates that dynamic block randomization outperforms minimization with regard to achieving balance and maximizing efficiency. Nevertheless, the differences across the three randomization strategies are modest. The statistical advantages associated with dynamic block randomization need to be considered in relation to the planned sample size and the practical issues for its implementation in deciding the preferred method of randomization for a given trial (e.g., the time required to accrue blocks of subjects of adequate size as balanced against the need to commence intervention/treatment immediately in those randomized to that experimental condition).

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