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1.
BMC Psychiatry ; 22(1): 114, 2022 02 14.
Article in English | MEDLINE | ID: mdl-35164737

ABSTRACT

BACKGROUND: Many second-generation antipsychotics (SGAs) are associated with weight gain and cardiometabolic effects. Antipsychotic-associated weight gain is linked to treatment interruptions, potentially increasing risk of relapse and hospitalization. This retrospective study assessed clinically significant weight gain (CSWG), treatment interruptions, and development of cardiometabolic conditions in patients with schizophrenia (SZ) or bipolar I disorder (BD-I) following initiation of oral SGAs with moderate to high weight gain risk. METHODS: Patients with no prior use of moderate to high weight gain risk oral SGAs were identified from patient-level medical/pharmacy claims and electronic medical records (January 2013-February 2020; OM1 Real-World Data Cloud). Those with ≥ 1 weight measurement in both the 12 months preceding and 3 months after SGA initiation (index date) were analyzed for continuous changes in weight, CSWG (≥ 7% and ≥ 10% increases from baseline), treatment interruptions (switches/discontinuations), and development of cardiometabolic conditions. RESULTS: Median follow-up times in the SZ (n = 8174) and BD-I (n = 9142) cohorts were 153.4 and 159.4 weeks, respectively; 45.5% and 50.7% were obese at baseline. Mean (SD) percent weight increase during treatment was 3.3% (7.2) and 3.7% (7.0) for patients with SZ and BD-I, respectively, and was highest for underweight/normal weight patients (SZ: 4.8% [8.1]; BD-I: 5.5% [8.7]). More than 96% had treatment interruptions during follow-up, primarily discontinuations. CSWG and treatment interruptions occurred within a median of 13 and 14 weeks after treatment initiation, respectively. Of patients with CSWG and treatment interruptions, approximately 75% did not return to baseline weight during follow-up. Among those without baseline cardiometabolic conditions, 14.7% and 11.3% of patients with SZ or BD-I, respectively, developed ≥ 1 condition over 12 months post-index. Incidence was generally highest among those who were overweight/obese at baseline and those who experienced CSWG. CONCLUSIONS: In this analysis of real-world data, both weight gain and treatment interruptions occurred early in treatment for patients with SZ or BD-I. Treatment-associated weight gain persisted despite switching or discontinuing index treatment. Additionally, cardiometabolic morbidity increased within 12 months of treatment initiation. Patients with SZ or BD-I are at greater risk than the general population for cardiometabolic conditions; weight gain associated with SGAs may exacerbate these health risks.


Subject(s)
Antipsychotic Agents , Bipolar Disorder , Cardiovascular Diseases , Schizophrenia , Antipsychotic Agents/adverse effects , Bipolar Disorder/drug therapy , Bipolar Disorder/epidemiology , Cardiovascular Diseases/chemically induced , Cardiovascular Diseases/epidemiology , Humans , Obesity/chemically induced , Obesity/drug therapy , Obesity/epidemiology , Overweight , Retrospective Studies , Schizophrenia/chemically induced , Schizophrenia/drug therapy , Weight Gain
2.
BMC Cancer ; 21(1): 785, 2021 Jul 07.
Article in English | MEDLINE | ID: mdl-34233640

ABSTRACT

BACKGROUND: Irreversible electroporation (IRE) is a local ablation technique utilizing high voltage, low energy direct current to create nanopores in cell membrane which disrupt homeostasis and leads to cell death. Previous reports have suggested IRE may have a role in treating borderline resectable and unresectable Stage 3 pancreatic tumors. METHODS: Patients with Stage 3 pancreatic ductal adenocarcinoma (PDAC) will be enrolled in either a randomized, controlled, multicenter trial (RCT) or a multicenter registry study. Subjects enrolled in the RCT must have no evidence of disease progression after 3 months of modified FOLFIRINOX (mFOLFIRINOX) treatment prior to being randomization to either a control or IRE arm. Post-induction and post-IRE treatment for the control and IRE arms, respectively, will be left to the discretion of the treating physician. The RCT will enroll 528 subjects with 264 per arm and include up to 15 sites. All subjects will be followed for at least 24 months or until death. The registry study will include two cohorts of patients with Stage 3 PDAC, patients who received institutional standard of care (SOC) alone and those treated with IRE in addition to SOC. Both cohorts will be required to have undergone at least 3 months of SOC without progression prior to enrollment. The registry study will enroll 532 patients with 266 patients in each arm. All patients will be followed for at least 24 months or until death. The primary efficacy endpoint for both studies will be overall survival (OS). Co-primary safety endpoints will be 1) time from randomization or enrollment in the registry to death or new onset of Grade 4 adverse event (AE), and (2 high-grade complications defined as any AE or serious AE (SAE) with a CTCAE v5.0 grade of 3 or higher. Secondary endpoints will include progression-free survival, cancer-related pain, quality of life, and procedure-related pain for the IRE arm only. DISCUSSION: These studies are intended to provide Level 1 clinical evidence and real-world data demonstrating the clinical utility and safety of the use of IRE in combination with chemotherapy in patients with Stage 3 PDAC. TRIAL REGISTRATION: Clinicaltrials.gov NCT03899636 and NCT03899649. Registered April 2, 2019. Food and Drug Administration (FDA) Investigational Device Exemption (IDE) trial G180278 approved on May 3, 2019.


Subject(s)
Ablation Techniques/methods , Adenocarcinoma/surgery , Pancreatic Neoplasms/surgery , Adenocarcinoma/mortality , Adenocarcinoma/pathology , Humans , Pancreatic Neoplasms/mortality , Pancreatic Neoplasms/pathology , Quality of Life , Randomized Controlled Trials as Topic , Registries , Survival Analysis , Treatment Outcome
3.
Respiration ; 99(2): 108-118, 2020.
Article in English | MEDLINE | ID: mdl-31982886

ABSTRACT

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is a life-threatening interstitial lung disease (ILD). Characterizing health outcomes of IPF patients is challenging due to disease rarity. OBJECTIVE: This study aimed to identify the burden of disease in patients newly diagnosed with IPF. METHODS: Patients with ≥1 claim with an IPF diagnosis were identified from a United States healthcare insurer's database (2000-2013). Patients with other known causes of ILD or aged <40 years were excluded. Subgroups were compared based on the 2011 change in International Classification of Diseases, 9th Revision (ICD-9) definition of IPF and occurrence of IPF testing. The prevalence and incidence of preselected health conditions of clinical interest were estimated. RESULTS: Median age of newly diagnosed patients (n = 7,298) was 62 years (54.0% male). Restricting to patients with IPF diagnostic testing did not substantially affect cohort characteristics, nor did ICD-9 IPF coding change. Mean follow-up was 1.7 years; 16.8% of patients died; and a substantial proportion of patients were censored due to end of health plan enrollment (50.7%) and other causes of ILD (19.6%). The incidence of pulmonary hypertension, lung cancer, and claims-based algorithm proxy for acute respiratory worsening of unknown cause was 22.5, 17.6, and 12.6 per 1,000 person-years, respectively. CONCLUSIONS: Patients with IPF had a high disease burden with a variety of health outcomes observed, including a high rate of mortality. Database censoring due to changes in enrollment or other ILD diagnoses limited follow-up. Altering cohort entry definitions, including IPF testing or ICD-9 IPF coding change, had little impact on cohort baseline characteristics.


Subject(s)
Glucocorticoids/therapeutic use , Health Care Costs , Hospitalization/statistics & numerical data , Idiopathic Pulmonary Fibrosis/therapy , Oxygen Inhalation Therapy , Adult , Aged , Aged, 80 and over , Anticoagulants , Bronchoalveolar Lavage , Cohort Studies , Databases, Factual , Disease Progression , Emergency Service, Hospital/statistics & numerical data , Female , Histamine H2 Antagonists/therapeutic use , Humans , Idiopathic Pulmonary Fibrosis/economics , Idiopathic Pulmonary Fibrosis/epidemiology , Incidence , Lung Neoplasms/epidemiology , Lung Transplantation , Male , Middle Aged , Myocardial Infarction/epidemiology , Outcome Assessment, Health Care , Platelet Aggregation Inhibitors , Prevalence , Proton Pump Inhibitors/therapeutic use , Pulmonary Arterial Hypertension/epidemiology , United States/epidemiology
4.
Curr Med Res Opin ; 38(3): 375-381, 2022 Mar.
Article in English | MEDLINE | ID: mdl-34951545

ABSTRACT

OBJECTIVE: To compare healthcare resource use (HCRU) in patients undergoing sinus surgery with or without steroid-eluting sinus implants. METHODS: A retrospective, observational cohort study using real-world evidence data (OM1, Inc, Boston, MA, USA) was conducted on adult patients with chronic rhinosinusitis (CRS) with or without nasal polyps who underwent endoscopic sinus surgery between 2014 and 2019 and had at least 18 months of data both before and after surgery. Patients receiving implants ("implant cohort") were matched to patients who did not receive implants ("non-implant cohort") based on a propensity score developed using baseline characteristics. Chi-square for binary variables and analysis of variance tests for continuous variables were applied to compare HCRU measures. RESULTS: Comparison of the implant (N = 1983) and non-implant (N = 1983) cohorts during the 18-month follow-up period demonstrated significantly lower HCRU in those receiving implants, including all-cause outpatient visits (94.3% vs. 96.6%, p < .001), all-cause otolaryngologist visits (47.3% vs. 59.6%, p < .001) and all cause ER/urgent care visits (9.2% vs. 11.8%, p = .007), as well as sinus-related endoscopies (39.1% vs. 43.8%, p = .003). Although not statistically significant, fewer patients in the implant cohort had undergone repeat surgeries (4.6% vs. 5.3%, p = .273). CONCLUSION: Patients with steroid-eluting sinus implants had lower HCRU over a post-operative period of 18 months. These findings support the contention that reductions in HCRU may be achieved using steroid-eluting implants during sinus surgery.What is known on this topicChronic rhinosinusitis (CRS) causes severe symptoms that lead to poor quality of life.Endoscopic sinus surgery (ESS) is 76-98% effective in improving CRS patients' symptoms.Surgical outcomes can be compromised in the immediate post-operative period by scarring, adhesion formation, and early polyp recurrence.Oral and topical corticosteroid therapy has become integral to the maintenance of successful surgical outcomes, the management of post-operative scarring and edema, and the prevention of nasal polyp recurrence.Steroid-eluting sinus implants have been shown in clinical trials to improve postoperative outcomes after ESS by delivering localized, sustained release of corticosteroids directly onto inflamed sinus tissue.What this study addsThis observational study is one of the first to use real-world evidence to assess the effect of steroid-eluting sinus implants on healthcare resource use (HCRU) in patients with chronic rhinosinusitis who underwent sinus surgery with or without implants.Use of implants significantly reduced HCRU, including all-cause outpatient visits (94.3% vs 96.6%, p < .001), all-cause otolaryngologist visits (47.3% vs 59.6%, p < .001), and all-cause ER/urgent care visits (9.2% vs 11.8%, p = .007), as well as sinus endoscopy (39.1% vs 43.8%, p = .003).Use of implants had no significant effect on sinus procedures such as debridement and polypectomy, as well as sinus-related imaging such as CT, MRI, and x-ray.


Subject(s)
Nasal Polyps , Rhinitis , Sinusitis , Adult , Chronic Disease , Cicatrix , Delivery of Health Care , Humans , Nasal Polyps/drug therapy , Quality of Life , Retrospective Studies , Rhinitis/drug therapy , Rhinitis/surgery , Sinusitis/drug therapy , Sinusitis/surgery , Steroids/therapeutic use , Treatment Outcome
5.
Am J Epidemiol ; 173(7): 731-8, 2011 Apr 01.
Article in English | MEDLINE | ID: mdl-21415029

ABSTRACT

The growing body of work in the epidemiology literature focused on G-computation includes theoretical explanations of the method but very few simulations or examples of application. The small number of G-computation analyses in the epidemiology literature relative to other causal inference approaches may be partially due to a lack of didactic explanations of the method targeted toward an epidemiology audience. The authors provide a step-by-step demonstration of G-computation that is intended to familiarize the reader with this procedure. The authors simulate a data set and then demonstrate both G-computation and traditional regression to draw connections and illustrate contrasts between their implementation and interpretation relative to the truth of the simulation protocol. A marginal structural model is used for effect estimation in the G-computation example. The authors conclude by answering a series of questions to emphasize the key characteristics of causal inference techniques and the G-computation procedure in particular.


Subject(s)
Causality , Epidemiologic Research Design , Models, Statistical , Computer Simulation , Confounding Factors, Epidemiologic , Humans , Regression Analysis
6.
Int J Environ Health Res ; 19(2): 139-55, 2009 Apr.
Article in English | MEDLINE | ID: mdl-19370464

ABSTRACT

Cross-sectional analyses were conducted to evaluate the effects of exposure to highway traffic on pulmonary function in Fresno, California. Traffic and spirometry data were available for 214 children (enrollment ages six to 11 years). Multiple linear regression was used to evaluate the relations between pulmonary function and traffic parameters. Heavy-duty vehicle count was used as a surrogate measure for diesel-related exposures. Pulmonary function was non-significantly associated with longer distance-to-road and non-significantly associated with higher traffic intensity. Evaluation of effect modification by FEF(25-75)/FVC (a measure of intrinsic airway size) showed that all pulmonary function measures of flow were significantly inversely related to a traffic metric that incorporates traffic intensity and roadway proximity. The results indicate that residence proximity to highway traffic is associated with lower pulmonary function among children with asthma, and smaller airway size is an important modifier of the effect of traffic exposure on pulmonary function and a marker of increased susceptibility.


Subject(s)
Asthma/physiopathology , Environmental Exposure , Lung/physiopathology , Vehicle Emissions/toxicity , Child , Cross-Sectional Studies , Female , Humans , Male , Regression Analysis , Residence Characteristics , Respiratory Function Tests
8.
J Expo Sci Environ Epidemiol ; 25(6): 567-73, 2015.
Article in English | MEDLINE | ID: mdl-25182844

ABSTRACT

Health effects of ambient air pollution are most frequently expressed in individual studies as responses to a standardized unit of air pollution changes (e.g., an interquartile interval), which is thought to enable comparison of findings across studies. However, this approach does not necessarily convey health effects in terms of a real-world air pollution scenario. In the present study, we use population intervention modeling to estimate the effect of an air pollution intervention that makes explicit reference to the observed exposure data and is identifiable in those data. We calculate the association between ambient summertime nitrogen dioxide (NO2) and forced expiratory flow between 25% and 75% of forced vital capacity (FEF25-75) in a cohort of children with asthma in Fresno, California. We scale the effect size to reflect NO2 abatement on a majority of summer days. The effect estimates were small, imprecise, and consistently indicated improved pulmonary function with decreased NO2. The effects ranged from -0.8% of mean FEF25-75 (95% confidence interval (CI): -3.4, 1.7) to -3.3% (95% CI: -7.5, 0.9). We conclude by discussing the nature and feasibility of the exposure change analyzed here given the observed air pollution profile, and we propose additional applications of population intervention models in environmental epidemiology.


Subject(s)
Air Pollutants/adverse effects , Asthma/chemically induced , Nitrogen Dioxide/adverse effects , Air Pollutants/analysis , California , Child , Female , Forced Expiratory Flow Rates/drug effects , Humans , Inhalation Exposure/adverse effects , Inhalation Exposure/analysis , Longitudinal Studies , Male , Models, Statistical , Nitrogen Dioxide/analysis , Prospective Studies , Vital Capacity/drug effects
9.
Article in English | MEDLINE | ID: mdl-25709706

ABSTRACT

BACKGROUND: Risk evaluation and mitigation strategies (REMS), as mandated by the US Food and Drug Administration (FDA) for medications with the potential for harm, are increasingly incorporating rigid protocols for patient evaluation, but little is known about compliance with these programs. Despite the inherent limitations, data on administrative claims may provide an opportunity to investigate adherence to these programs. METHODS: We assessed adherence to liver function test (LFT) requirements included in the REMS program for bosentan through use of administrative claims. Patients observed in the Optum Research Database who were initiators of bosentan from November 20, 2001 to March 31, 2013 were included. Adherence to LFTs was calculated using pharmacy claims for bosentan dispensation and medical claims for laboratory services, and was assessed at the time of drug initiation and within specified time intervals throughout follow-up. RESULTS: Of 742 patients, 523 (70.5%) had ≥1 qualifying LFT. Among patients with ≥12 dispensations, claims for LFTs at individual dispensations were 53.2-64.0%. Median proportion of dispensations with ≥1 LFT was 0.8 among patients with ≥6 (interquartile range, 0.7-1.0) or ≥12 (0.7-0.9) dispensations. Adherence was 90-100% for 33.3% of all initiators, whereas 29.3% of initiators were non-adherent (defined as <50% of on-therapy LFTs). CONCLUSIONS: Analyses of administrative claims suggest that the REMS program for bosentan may not have adequately guaranteed adherence to the program's monthly monitoring of LFTs. Such investigations of existing REMS programs may provide insight on how to accomplish more successful evaluation of REMS.

10.
Chest ; 123(6): 1899-907, 2003 Jun.
Article in English | MEDLINE | ID: mdl-12796166

ABSTRACT

STUDY OBJECTIVES: Laboratory-based spirometry is the "gold standard" for the assessment of lung function, both in clinical and research protocols. These spirometers, however, are neither practical nor affordable for home-based monitoring or studies that collect data in multiple locations. Traditionally, peak flowmeters have been used, but they have important limitations. DESIGN: Based on data from a cohort of 92 children with asthma, we evaluated the agreement between a portable spirometer and a office-based spirometer, using an in-line technique to evaluate measures from the same effort. We compared a range of pulmonary function parameters collected during office-based tests, and also evaluated whether adequate adherence and data quality could be achieved in a home-based study of children with asthma. RESULTS: The agreement between the devices for the actual values of peak expiratory flow, FEV(1), and forced expiratory flow at 25% of FVC was excellent. The portable device was programmed with customized software to grade each curve using revised American Thoracic Society acceptability and reproducibility criteria. For 74% of the curves, quality grade agreed with a grade assigned by physician review of the curve from the office-based spirometer. During 2 weeks of twice-daily monitoring at home, children completed an average of 23 of 28 possible sessions (83%). Of these, 84% had at least two acceptable and two reproducible curves. Although children >or= 8 years old were not more adherent, they were significantly more likely to achieve acceptable and reproducible curves. CONCLUSIONS: Portable spirometers can provide measurements that are highly comparable to those obtained from "gold standard" laboratory spirometers, and high-quality tracings can be achieved both at home and in the office setting. Visual inspection of the curves by experienced reviewers identified unacceptable curves that were not rejected by the quality control software. Portable spirometers are an important contribution to epidemiologic and clinical studies that require frequent measures of a more broad range of pulmonary function parameters than can be provided by peak flowmeters.


Subject(s)
Asthma/physiopathology , Spirometry/instrumentation , Child , Forced Expiratory Flow Rates , Home Care Services , Humans , Peak Expiratory Flow Rate
11.
Ann Epidemiol ; 24(12): 888-95e4, 2014 Dec.
Article in English | MEDLINE | ID: mdl-25453347

ABSTRACT

PURPOSE: To evaluate associations between traffic-related air pollution during pregnancy and preterm birth in births in four counties in California during years 2000 to 2006. METHODS: We used logistic regression to examine the association between the highest quartile of ambient air pollutants (carbon monoxide, nitrogen dioxide, particulate matter <10 and 2.5 µm) and traffic density during pregnancy and each of five levels of prematurity based on gestational age at birth (20-23, 24-27, 28-31, 32-33, and 34-36 weeks) versus term (37-42 weeks). We examined trimester averages and the last month and the last 6 weeks of pregnancy. Models were adjusted for birthweight, maternal age, race/ethnicity, education, prenatal care, and birth costs payment. Neighborhood socioeconomic status (SES) was evaluated as a potential effect modifier. RESULTS: There were increased odds ratios (ORs) for early preterm birth for those exposed to the highest quartile of each pollutant during the second trimester and the end of pregnancy (adjusted OR, 1.4-2.8). Associations were stronger among mothers living in low SES neighborhoods (adjusted OR, 2.1-4.3). We observed exposure-response associations for multiple pollutant exposures and early preterm birth. Inverse associations during the first trimester were observed. CONCLUSIONS: The results confirm associations between traffic-related air pollution and prematurity, particularly among very early preterm births and low SES neighborhoods.


Subject(s)
Air Pollutants/toxicity , Air Pollution/adverse effects , Pregnancy Outcome/epidemiology , Premature Birth/chemically induced , Vehicle Emissions/toxicity , Adult , Air Pollutants/analysis , Birth Weight/drug effects , California/epidemiology , Carbon Monoxide/analysis , Carbon Monoxide/toxicity , Female , Gestational Age , Humans , Infant, Newborn , Logistic Models , Male , Maternal Age , Maternal Exposure , Nitrogen Oxides/analysis , Nitrogen Oxides/toxicity , Particulate Matter/analysis , Particulate Matter/toxicity , Pregnancy , Premature Birth/epidemiology , Residence Characteristics , Risk Assessment , Vehicle Emissions/analysis , Young Adult
12.
Environ Health Perspect ; 118(10): 1497-502, 2010 Oct.
Article in English | MEDLINE | ID: mdl-20570778

ABSTRACT

BACKGROUND: Although studies have demonstrated that air pollution is associated with exacerbation of asthma symptoms in children with asthma, little is known about the susceptibility of subgroups, particularly those with atopy. OBJECTIVE: This study was designed to evaluate our a priori hypothesis that identifiable subgroups of asthmatic children are more likely to wheeze with exposure to ambient air pollution. METHODS: A cohort of 315 children with asthma, 6-11 years of age, was recruited for longitudinal follow-up in Fresno, California (USA). During the baseline visit, children were administered a respiratory symptom questionnaire and allergen skin-prick test. Three times a year, participants completed 14-day panels during which they answered symptom questions twice daily. Ambient air quality data from a central monitoring station were used to assign exposures to the following pollutants: particulate matter ≤ 2.5 µm in aerodynamic diameter, particulate matter between 2.5 and 10 µm in aerodynamic diameter (PM10-2.5), elemental carbon, nitrogen dioxide (NO2), nitrate, and O3. RESULTS: For the group as a whole, wheeze was significantly associated with short-term exposures to NO2 [odds ratio (OR) = 1.10 for 8.7-ppb increase; 95% confidence interval (CI), 1.02-1.20] and PM10-2.5 (OR = 1.11 for 14.7-µg/m3 increase; 95% CI, 1.01-1.22). The association with wheeze was stronger for these two pollutants in children who were skin-test positive to cat or common fungi and in boys with mild intermittent asthma. CONCLUSION: A pollutant associated with traffic emissions, NO2, and a pollutant with bioactive constituents, PM10-2.5, were associated with increased risk of wheeze in asthmatic children living in Fresno, California. Children with atopy to cat or common fungi and boys with mild intermittent asthma were the subgroups for which we observed the largest associations.


Subject(s)
Air Pollutants/toxicity , Asthma/physiopathology , Respiratory Sounds/etiology , Asthma/complications , California , Child , Humans , Surveys and Questionnaires
13.
Pediatr Allergy Immunol ; 16(8): 669-78, 2005 Dec.
Article in English | MEDLINE | ID: mdl-16343089

ABSTRACT

This study addressed the comparability of data obtained from a student-based and parent-based asthma and respiratory health survey. Our goal was to ascertain whether there were meaningful and systematic differences in asthma classification based on symptom and diagnosis reports obtained separately from students and their parents. A brief, written survey, based on the International Study of Asthma and Allergy in Children questionnaire, was administered to 6th through 10th grade students in two schools in Oakland, CA, USA. Students who reported asthma-like indicators for the previous 12-month period were defined as positive and a more extensive questionnaire was mailed home to those parents. A more refined classification of asthma based on parent report of indicators was compared with student report. Forty-four percent of 1298 students were classified as positive for current asthma-like symptoms and 50% of parent surveys were returned. For the positive students with parent surveys, 59% were classified as 'probable' for asthma based on the parent survey. Overall, the agreement between parent and students' classification was 70%, and 83% for students with a parent report of physician diagnosis of asthma. Students who were discordant with parents for physician diagnosis of asthma were more likely to be male, and more likely to have a parent report of unscheduled Emergency Department visit for wheezing or trouble breathing. Findings indicated that with the exception of medication, students reported asthma indicators more frequently that parents, independent of classification. Student report of physician diagnosis with a 12-month report of an asthma symptom was determined to be a good indicator of probable current asthma. Inclusion of or reliance on a parental questionnaire is not likely to improve the reliability of a school-based asthma surveillance program in our population.


Subject(s)
Asthma/diagnosis , Asthma/epidemiology , Health Surveys , Parents , Population Surveillance , Students , Adolescent , Adult , Asthma/physiopathology , Child , Female , Humans , Male , Reproducibility of Results , Surveys and Questionnaires
14.
Am J Epidemiol ; 162(4): 382-8, 2005 Aug 15.
Article in English | MEDLINE | ID: mdl-16014771

ABSTRACT

Marginal structural models (MSMs) are being used more frequently to obtain causal effect estimates in observational studies. Although the principal estimator of MSM coefficients has been the inverse probability of treatment weight (IPTW) estimator, there are few published examples that illustrate how to apply IPTW or discuss the impact of model selection on effect estimates. The authors applied IPTW estimation of an MSM to observational data from the Fresno Asthmatic Children's Environment Study (2000-2002) to evaluate the effect of asthma rescue medication use on pulmonary function and compared their results with those obtained through traditional regression methods. Akaike's Information Criterion and cross-validation methods were used to fit the MSM. In this paper, the influence of model selection and evaluation of key assumptions such as the experimental treatment assignment assumption are discussed in detail. Traditional analyses suggested that medication use was not associated with an improvement in pulmonary function--a finding that is counterintuitive and probably due to confounding by symptoms and asthma severity. The final MSM estimated that medication use was causally related to a 7% improvement in pulmonary function. The authors present examples that should encourage investigators who use IPTW estimation to undertake and discuss the impact of model-fitting procedures to justify the choice of the final weights.


Subject(s)
Air Pollutants/adverse effects , Asthma/etiology , Epidemiologic Methods , Models, Statistical , Peak Expiratory Flow Rate/drug effects , Anti-Asthmatic Agents/therapeutic use , Asthma/drug therapy , California/epidemiology , Child , Humans , Respiratory Sounds/etiology
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