[Show abstract][Hide abstract] ABSTRACT: Background:
Classifying medication adherence is important for efficiently targeting adherence improvement interventions. The purpose of this study was to evaluate the use of a novel method, group-based trajectory models, for classifying patients by their long-term adherence.
We identified patients who initiated a statin between June 1, 2006 and May 30, 2007 in prescription claims from CVS Caremark and evaluated adherence over the subsequent 15 months. We compared several adherence summary measures, including proportion of days covered (PDC) and trajectory models with 2-6 groups, with the observed adherence pattern, defined by monthly indicators of full adherence (defined as having ≥24 d covered of 30). We also compared the accuracy of adherence prediction based on patient characteristics when adherence was defined by either a trajectory model or PDC.
In 264,789 statin initiators, the 6-group trajectory model summarized long-term adherence best (C=0.938), whereas PDC summarized less well (C=0.881). The accuracy of adherence predictions was similar whether adherence was classified by PDC or by trajectory model.
Trajectory models summarized adherence patterns better than traditional approaches and were similarly predicted by covariates. Group-based trajectory models may facilitate targeting of interventions and may be useful to adjust for confounding by health-seeking behavior.
Medical care 05/2013; 51(9). DOI:10.1097/MLR.0b013e3182984c1f · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Six oral medication classes have been approved by the Food and Drug Administration for the treatment of type 2 diabetes. Although all of these agents effectively lower blood glucose, the evidence supporting their impact on other clinical events is variable. There also are substantial cost differences between agents. We aimed to evaluate temporal trends in the use of specific drugs for the initial management of type 2 diabetes and to estimate the economic consequences of non-recommended care.
We studied a cohort of 254,973 patients, aged 18 to 100 years, who were newly initiated on oral hypoglycemic monotherapy between January 1, 2006, and December 31, 2008, by using prescription claims data from a large pharmacy benefit manager. Linear regression models were used to assess whether medication initiation patterns changed over time. Multivariate logistic regression models were constructed to identify independent predictors of receiving initial therapy with metformin. We then measured the economic consequences of prescribing patterns by drug class for both patients and the insurer.
Over the course of the study period, the proportion of patients initially treated with metformin increased from 51% to 65%, whereas those receiving sulfonylureas decreased from 26% to 18% (P<.001 for both). There was a significant decline in the use of thiazolidinediones (20.1%-8.3%, P<.001) and an increase in prescriptions for dipeptidyl peptidase-4 inhibitors (0.4%-7.3%, P<.001). Younger patients, women, and patients receiving drug benefits through Medicare were least likely to initiate treatment with metformin. Combined patient and insurer spending for patients who were initiated on alpha-glucosidase inhibitors, thiazolidinediones, meglitinides, or dipeptidyl peptidase-4 inhibitors was $677 over a 6-month period compared with $116 and $118 for patients initiated on metformin or a sulfonylurea, respectively, a cost difference of approximately $1120 annually per patient.
Approximately 35% of patients initiating an oral hypoglycemic drug did not receive recommended initial therapy with metformin. These practice patterns also have substantial implications for health care spending.
The American journal of medicine 03/2012; 125(3):302.e1-7. DOI:10.1016/j.amjmed.2011.07.033 · 5.00 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Patients with chronic disease often take many medications multiple times per day. Such regimen complexity is associated with medication nonadherence. Other factors, including the number of pharmacy visits patients make to pick up their prescriptions, may also undermine adherence. Our objective was to estimate the extent of prescribing and filling complexity in patients prescribed a cardiovascular medication and to evaluate its association with adherence.
The study population comprised individuals prescribed a statin (n = 1 827 395) or an angiotensin- converting enzyme inhibitor or renin angiotensin receptor blocker (ACEI/ARB) (n = 1 480 304) between June 1, 2006, and May 30, 2007. We estimated complexity by measuring the number of medications, prescribers, pharmacies, pharmacy visits, and refill consolidation (a measure of the number of visits per fill) during the 3 months from the first prescription. The number of daily doses was also measured in ACEI/ARB users. After this period, adherence was evaluated over the subsequent year. The relationship between complexity and adherence was assessed with multivariable linear regression.
The statin cohort had a mean age of 63 years and were 49% male. On average, during the 3-month complexity assessment period, statin users filled 11.4 prescriptions for 6.3 different medications, had prescriptions written by 2 prescribers, and made 5.0 visits to the pharmacy. Results for ACEI/ARB users were similar. Greater prescribing and filling complexity was associated with lower levels of adherence. In adjusted models, patients with the least refill consolidation had adherence rates that were 8% lower over the subsequent year than patients with the greatest refill consolidation.
Medication use and prescription filling for patients with cardiovascular disease is complex, and strategies to reduce this complexity may help improve medication adherence.
Archives of internal medicine 05/2011; 171(9):814-22. DOI:10.1001/archinternmed.2010.495 · 17.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Immigration to the United States presents both challenges and opportunities that affect students' academic achievement. Using a 5-year longitudinal, mixed-methods approach, we identified varying academic trajectories of newcomer immigrant students from Central America, China, the Dominican Republic, Haiti, and Mexico. Latent class growth curve analysis revealed that although some newcomer students performed at high or improving levels over time, others showed diminishing performance. Multinomial logistic regressions identified significant group differences in academic trajectories, particularly between the high-achieving youth and the other groups. In keeping with ecological-developmental and stage-environment fit theories, School Characteristics (school segregation rate, school poverty rate, and student perceptions of school violence), Family Characteristics (maternal education, parental employment, and household structure), and Individual Characteristics (academic English proficiency, academic engagement, psychological symptoms, gender, and 2 age-related risk factors, number of school transitions and being overaged for grade placement) were associated with different trajectories of academic performance. A series of case studies triangulate many of the quantitative findings as well as illuminate patterns that were not detected in the quantitative data. Thus, the mixed-methods approach sheds light on the cumulative developmental challenges that immigrant students face as they adjust to their new educational settings.
[Show abstract][Hide abstract] ABSTRACT: Background: While a significant body of research has addressed teachers' evaluations of mainstream English speaking students, there is a dearth of such research focusing on immigrant adolescents. As many immigrant students are in the process of acquiring English language proficiency, evaluating and assigning grades to immigrant youth can pose particular challenges. Grades assigned for oral or written products may underestimate English language learners' knowledge, content skills or achievement. Conversely, relying excessively on effort or class behaviour rather than actual academic performance may inflate immigrant students' grades.Purpose: We examined the extent to which immigrant students' academic achievement indicated by grades is attributable to factors such as English language proficiency, course understanding, classroom behaviours and homework completion. We then examined whether the effect of homework completion on grades varied as a function of English proficiency. In addition, we examined the factors contributing to teachers' evaluation of immigrant students' level of course understanding. Lastly, we investigated whether the effect of homework completion on course understanding varied as a function of English proficiency.Sample: This study examined the final year (2002) data of the five-year Longitudinal Immigrant Student Adaptation (LISA) study. At the start of the original study, the participants were recently arrived immigrant youth (ages 9–14) from Central America (El Salvador, Guatemala, Honduras and Nicaragua), China, the Dominican Republic, Haiti and Mexico; they were recruited from seven public school districts in the USA in Massachusetts and California. The present study was a secondary analysis of a subset of final year LISA data, involving data from 273 students and 57 teachers.Methods: Using data collected through structured student interviews and behaviour checklists completed by teachers, we conducted hierarchical regression analyses to identify the factors that contributed significantly to immigrant students' grades and to their course understanding. Further regression analyses were conducted to determine whether English language proficiency was a moderating variable on immigrant students' grades and their level of understanding in a course.Results: There were four main findings. Firstly, the regression results indicated that homework completion and English language proficiency had significant impact on class grades. Secondly, the effect of homework completion on grades was not moderated by students' English proficiency. Thirdly, immigrant students' class behaviours, English proficiency and homework completion largely determined teacher evaluations of students' course understanding. Fourthly, the effect of homework completion on teacher evaluations of students' course understanding was moderated by English proficiency. For students with high English language proficiency, completing homework significantly affected teacher assessments of their course understanding. For students with low English language proficiency, however, completing homework had relatively little effect on teacher assessments of their course understanding.Conclusions: In this exploratory study, grades assigned to immigrant students were largely determined by whether they do their homework and their English language proficiency. Teacher evaluations of immigrant students' level of course understanding were largely determined by students' class behaviours, English language proficiency and homework completion. It is suggested that teachers distinguish between effort and skill and provide separate feedback for each of these dimensions during the process that newcomer immigrant students are concurrently acquiring academic skills while mastering a new language. However, further investigation is needed to determine the generalisability of findings to a larger immigrant youth population.
Educational Research 03/2009; 51(1):1-25. DOI:10.1080/00131880802704624 · 0.48 Impact Factor