Jason Nelson

The Boston Puerto Rican Health Study, a longitudinal cohort study on health disparities in Puerto Rican adults: challenges and opportunities.

BackgroundThe Boston Puerto Rican Health Study is an ongoing longitudinal cohort study designed to examine the role of psychosocial stress on presence and development of allostatic load and health outcomes in Puerto Ricans, and potential modification by nutritional status, genetic variation, and social support.MethodsSelf-identified Puerto Ricans, aged 45-75 years and residing in the Boston, MA metro area, were recruited through door-to-door enumeration and community approaches. Participants completed a comprehensive set of questionnaires and tests. Blood, urine and salivary samples were extracted for biomarker and genetic analysis. Measurements are repeated at a two-year follow-up.ResultsA total of 1500 eligible participants completed baseline measurements, with nearly 80% two-year follow-up retention. The majority of the cohort is female (70%), and many have less than 8th grade education (48%), and fall below the poverty level (59%). Baseline prevalence of health conditions is high for this age range: considerable physical (26%) and cognitive (7%) impairment, obesity (57%), type 2 diabetes (40%), hypertension (69%), arthritis (50%) and depressive symptomatology (60%).ConclusionsThe enrollment of minority groups presents unique challenges. This report highlights approaches to working with difficult to reach populations, and describes some of the health issues and needs of Puerto Rican older adults. These results may inform future studies and interventions aiming to improve the health of this and similar communities.

Plasma 25-hydroxyvitamin D and progression to diabetes in patients at risk for diabetes: an ancillary analysis in the Diabetes Prevention Program.

OBJECTIVE To investigate the association between vitamin D status, assessed by plasma 25-hydroxyvitamin D, and risk of incident diabetes. RESEARCH DESIGN AND METHODS Prospective observational study with a mean follow-up of 2.7 years in the Diabetes Prevention Program (DPP), a multicenter trial comparing different strategies for prevention of diabetes in patients with prediabetes. We assessed the association between plasma 25-hydroxyvitamin D, measured repeatedly during follow-up, and incident diabetes in the combined placebo (n = 1,022) and intensive lifestyle (n = 1,017) randomized arms of the DPP. Variables measured at multiple study time points (25-hydroxyvitamin D, BMI, and physical activity) entered the analyses as time-varying “lagged” covariates, as the mean of the previous and current visits at which diabetes status was assessed. RESULTS After multivariate adjustment, including for the DPP intervention, participants in the highest tertile of 25-hydroxyvitamin D (median concentration, 30.1 ng/mL) had a hazard ratio of 0.72 (95% CI 0.56–0.90) for developing diabetes compared with participants in the lowest tertile (median concentration, 12.8 ng/mL). The association was in the same direction in placebo (0.70; 0.52–0.94) versus lifestyle arm (0.80; 0.54–1.17). CONCLUSIONS Higher plasma 25-hydroxyvitamin D, assessed repeatedly, was associated with lower risk of incident diabetes in high-risk patients, after adjusting for lifestyle interventions (dietary changes, increased physical activity, and weight loss) known to decrease diabetes risk. Because of the observational nature of the study, the potential association between vitamin D and diabetes needs to be confirmed in intervention studies.

Geographic access to burn center hospitals.

CONTEXT The delivery of burn care is a resource-intensive endeavor that requires specialized personnel and equipment. The optimal geographic distribution of burn centers has long been debated; however, the current distribution of centers relative to geographic area and population is unknown. OBJECTIVE To estimate the proportion of the US population living within 1 and 2 hours by rotary air transport (helicopter) or ground transport of a burn care facility. DESIGN AND SETTING A cross-sectional analysis of geographic access to US burn centers utilizing the 2000 US census, road and speed limit data, the Atlas and Database of Air Medical Services database, and the 2008 American Burn Association Directory. MAIN OUTCOME MEASURE The proportion of state, regional, and national population living within 1 and 2 hours by air transport or ground transport of a burn care facility. RESULTS In 2008, there were 128 self-reported burn centers in the United States including 51 American Burn Association-verified centers. An estimated 25.1% and 46.3% of the US population live within 1 and 2 hours by ground transport, respectively, of a verified burn center. By air, 53.9% and 79.0% of the population live within 1 and 2 hours, respectively, of a verified center. There was significant regional variation in access to verified burn centers by both ground and rotary air transport. The greatest proportion of the population with access was highest in the northeast region and lowest in the southern United States. CONCLUSION Nearly 80% of the US population lives within 2 hours by ground or rotary air transport of a verified burn center; however, there is both state and regional variation in geographic access to these centers.

A Percutaneous Coronary Intervention Lab in Every Hospital

Background— In 2001, 1176 US hospitals were capable of performing primary percutaneous coronary intervention (PCI), and 79% of the population lived within 60-minute ground transport of these hospitals. We compared these estimates with data from 2006 to explore how hospital PCI capability and population access have changed over time. Methods and Results— We estimated the proportion of the population 18 years of age or older, living in 2006 within a 60-minute drive of a PCI-capable hospital, and we compared our estimate with a previously published report on 2001 data. Over the 5-year period, the number of PCI-capable hospitals grew from 1176 to 1695 hospitals, a relative increase of 44%; access to the procedure grew from 79.0% to 79.9% of the population, a relative increase of 1%. Conclusions— Our data indicate a large increase in the number of hospitals capable of performing PCI from 2001 to 2006, but this increase was not associated with an appreciable change in the proportion of the population with access to the procedure. In the future, more attention is needed on changes in PCI capacity over time and on the effects of these changes on outcomes of interest such as service utilization, expenditures, patient outcomes, and population health.

Improving diabetes prevention with benefit based tailored treatment: risk based reanalysis of Diabetes Prevention Program

Objective To determine whether some participants in the Diabetes Prevention Program were more or less likely to benefit from metformin or a structured lifestyle modification program. Design Post hoc analysis of the Diabetes Prevention Program, a randomized controlled trial. Setting Ambulatory care patients. Participants 3060 people without diabetes but with evidence of impaired glucose metabolism. Intervention Intervention groups received metformin or a lifestyle modification program with the goals of weight loss and physical activity. Main outcome measure Development of diabetes, stratified by the risk of developing diabetes according to a diabetes risk prediction model. Results Of the 3081 participants with impaired glucose metabolism at baseline, 655 (21%) progressed to diabetes over a median 2.8 years’ follow-up. The diabetes risk model had good discrimination (C statistic=0.73) and calibration. Although the lifestyle intervention provided a sixfold greater absolute risk reduction in the highest risk quarter than in the lowest risk quarter, patients in the lowest risk quarter still received substantial benefit (three year absolute risk reduction 4.9% v 28.3% in highest risk quarter; numbers needed to treat of 20.4 and 3.5, respectively). The benefit of metformin, however, was seen almost entirely in patients in the top quarter of risk of diabetes. No benefit was seen in the lowest risk quarter. Participants in the highest risk quarter averaged a 21.4% three year absolute risk reduction (number needed to treat 4.6). Conclusions Patients at high risk of diabetes have substantial variation in their likelihood of receiving benefit from diabetes prevention treatments. Using this knowledge could decrease overtreatment and make prevention of diabetes far more efficient, effective, and patient centered, provided that decision making is based on an accurate risk prediction tool.

Using Internally Developed Risk Models to Assess Heterogeneity in Treatment Effects in Clinical Trials

Background—Recent proposals suggest that risk-stratified analyses of clinical trials be routinely performed to better enable tailoring of treatment decisions to individuals. Trial data can be stratified using externally developed risk models (eg, Framingham risk score), but such models are not always available. We sought to determine whether internally developed risk models, developed directly on trial data, introduce bias compared with external models. Methods and Results—We simulated a large patient population with known risk factors and outcomes. Clinical trials were then simulated by repeatedly drawing from the patient population assuming a specified relative treatment effect in the experimental arm, which either did or did not vary according to a subject’s baseline risk. For each simulated trial, 2 internal risk models were developed on either the control population only (internal controls only) or the whole trial population blinded to treatment (internal whole trial). Bias was estimated for the internal models by comparing treatment effect predictions to predictions from the external model. Under all treatment assumptions, internal models introduced only modest bias compared with external models. The magnitude of these biases was slightly smaller for internal whole trial models than for internal controls only models. Internal whole trial models were also slightly less sensitive to bias introduced by overfitting and less sensitive to falsely identifying the existence of variability in treatment effect across the risk spectrum compared with internal controls only models. Conclusions—Appropriately developed internal models produce relatively unbiased estimates of treatment effect across the spectrum of risk. When estimating treatment effect, internally developed risk models using both treatment arms should, in general, be preferred to models developed on the control population.

Evidence of systematic duplication by new percutaneous coronary intervention programs.

Background—Evidence suggests that recent and projected future investments in percutaneous coronary intervention (PCI) programs at US hospitals fail to increase access to timely reperfusion for patients with ST-segment elevation myocardial infarction. Methods and Results—We set out to estimate the annual number and costs of new PCI programs in US hospitals from 2004 to 2008 and identify the characteristics of hospitals, neighborhoods, and states where new PCI programs have been introduced. We estimated a discrete-time hazard model to measure the influence of these characteristics on the decision of a hospital to introduce a new PCI program. In 2008, 1739 US hospitals were capable of performing PCI, a relative increase of 16.5% (251 hospitals) over 2004. The percentage of the US population with projected access to timely PCI grew by 1.8%. New PCI programs were more likely to be introduced in areas that already had a PCI program with more competition for market share, near populations with higher rates of private insurance, in states that had weak or no regulation of new cardiac catheterization laboratories, and in wealthier and larger hospitals. Conclusions—Our data show that new PCI programs were systematically duplicative of existing programs and did not help patients gain access to timely PCI. The total cost of recent US investments in new PCI programs is large and of questionable value for patients.

Vitamin D status of black and white Americans and changes in vitamin D metabolites after varied doses of vitamin D supplementation

BACKGROUND Controversy exists over the disparate circulating 25-hydroxyvitamin D [25(OH)D] concentrations between black and white Americans. OBJECTIVE We sought to determine whether there are differences in total and directly measured free 25(OH)D concentrations between black and white American adults and how daily supplementation with cholecalciferol changes these concentrations. DESIGN Cross-sectional and longitudinal analyses were conducted with the use of data from 2 placebo-controlled, randomized trials at 2 academic medical centers in the United States: CaDDM (Calcium and Vitamin D in Type 2 Diabetes) and DDM2 (Vitamin D for Established Type 2 Diabetes). A total of 208 subjects with pre- or well-controlled diabetes with a mean age of 59.1 y and mean body mass index (BMI; in kg/m(2)) of 31.6 were randomly assigned to receive daily cholecalciferol supplementation at 1 of 2 doses (2000 or 4000 IU) or a matching placebo for 16 wk. We measured serum total 25(OH)D, vitamin D-binding protein (DBP) by 2 different immunoassays (with the use of monoclonal or polyclonal antibodies), parathyroid hormone, and albumin. Free 25(OH)D concentration was directly measured and calculated. RESULTS Blacks had lower total 25(OH)D concentrations than whites [adjusted median: 20.3 ng/mL (95% CI: 16.2, 24.5 ng/mL) compared with 26.7 ng/mL (95% CI: 25.2, 28.1 ng/mL), respectively; P = 0.026)], and a higher proportion of blacks had total 25(OH)D concentrations <20 ng/mL (46% compared with 19%, respectively; P < 0.001). Directly measured free 25(OH)D concentrations were lower in blacks than in whites [adjusted median: 4.5 ng/mL (95% CI: 3.7, 5.4 ng/mL) compared with 5.7 ng/mL (95% CI: 5.4, 5.9 ng/mL), respectively; P = 0.044] and were strongly correlated with total 25(OH)D without an effect of race. DBP was lower in blacks when measured by the monoclonal but not the polyclonal antibody immunoassay. Cholecalciferol supplementation increased total and measured free 25(OH)D concentrations proportionally to the dose and without a difference between races. CONCLUSIONS The relation between free and total 25(OH)D did not vary systematically by race in this multiracial population with pre- or well-controlled diabetes. The results need to be replicated in additional cohorts before concluding that the clinical assessment of vitamin D status in blacks and whites should follow a single standard. The CaDDM and DDM2 trials were registered at clinicaltrials.gov as NCT00436475 and NCT01736865, respectively.

Risk and treatment effect heterogeneity: re-analysis of individual participant data from 32 large clinical trials

Background Risk of the outcome is a mathematical determinant of the absolute treatment benefit of an intervention, yet this can vary substantially within a trial population, complicating the interpretation of trial results. Methods We developed risk models using Cox or logistic regression on a set of large publicly available randomized controlled trials (RCTs). We evaluated risk heterogeneity using the extreme quartile risk ratio (EQRR, the ratio of outcome rates in the lowest risk quartile to that in the highest) and skewness using the median to mean risk ratio (MMRR, the ratio of risk in the median risk patient to the average). We also examined heterogeneity of treatment effects (HTE) across risk strata. Results We describe 39 analyses using data from 32 large trials, with event rates across studies ranging from 3% to 63% (median = 15%, 25th-75th percentile = 9-29%). C-statistics of risk models ranged from 0.59 to 0.89 (median = 0.70, 25th-75th percentile = 0.65-0.71). The EQRR ranged from 1.8 to 50.7 (median = 4.3, 25th-75th percentile = 3.0-6.1). The MMRR ranged from 0.4 to 1.0 (median = 0.86, 25th-75th percentile = 0.80-0.92). EQRRs were predictably higher and MMRRs predictably lower as the c-statistic increased or the overall outcome incidence decreased. Among 18 comparisons with a significant overall treatment effect, there was a significant interaction between treatment and baseline risk on the proportional scale in only one. The difference in the absolute risk reduction between extreme risk quartiles ranged from -3.2 to 28.3% (median = 5.1%; 25th-75th percentile = 0.3-10.9). Conclusions There is typically substantial variation in outcome risk in clinical trials, commonly leading to clinically significant differences in absolute treatment effects Most patients have outcome risks lower than the trial average reflected in the summary result. Risk-stratified trial analyses are feasible and may be clinically informative, particularly when the outcome is predictable and uncommon.

Comparative outcomes of β-lactam antibiotics in outpatient parenteral antibiotic therapy: treatment success, readmissions and antibiotic switches

OBJECTIVES β-Lactam antibiotics are commonly used in outpatient parenteral antimicrobial therapy (OPAT), but data regarding outcomes of long-term therapy are limited. The purpose of this study was to compare treatment success, readmission and antibiotic switch rates in patients treated with β-lactam antibiotics as OPAT. METHODS We carried out a retrospective review of all patients, discharged from Tufts Medical Center with cefazolin, ceftriaxone, ertapenem or oxacillin, between January 2009 and June 2013. A competing risks analysis was used to compare the cumulative incidence of first occurrence of treatment success, antibiotic switch and 30 day readmission for each drug. RESULTS Four hundred patients were identified (cefazolin n = 38, ceftriaxone n = 104, ertapenem n = 128 and oxacillin n = 130). Baseline demographics were similar. Treatment success rates were higher for ceftriaxone and ertapenem (cefazolin 61%, ceftriaxone 81%, ertapenem 73% and oxacillin 58%; P < 0.001). Thirty-day all-cause readmissions were similar (cefazolin 21%, ceftriaxone 14%, ertapenem 20% and oxacillin 15%; P = 0.46). In 400 OPAT courses, 37 out of 50 antibiotic switches were accomplished without readmission. Adverse drug events (ADEs) were the most common reason for outpatient antibiotic switches (31/37, 84%). The ADE rate was higher for the oxacillin group (cefazolin 2.0 versus ceftriaxone 1.5 versus ertapenem 2.9 versus oxacillin 8.4 per 1000 OPAT days; P < 0.001). CONCLUSIONS OPAT with β-lactam antibiotics is effective, but antibiotic switches for adverse events were more frequent with oxacillin use. Clinicians should be cognizant of the risk of readmissions and ADEs in OPAT patients, as the value of OPAT lies in reducing patient morbidity and readmissions by managing ADEs and preventing clinical failures.