* Candidate for the Lee B. Lusted Student Prize Competition
Purpose: The effectiveness of acute geriatric units in improving outcomes of hospitalized seniors in the real world is unclear. We sought to answer this question by focusing on pneumonia. We hypothesized that acute geriatric units reduce short-term mortality for seniors hospitalised for pneumonia compared with those receiving usual internal medicine care.
Method: We merged medical records and administrative data of adults aged 65 years or older admitted to 3 acute care hospitals over one year. The outcome variable was 30-day mortality. The treatment variable was admission to acute geriatric units, with usual internal medical care as the reference. Other explanatory variables included demography, admission information, severity of acute illness (CURB score), co-morbidity, and functional status. We obtained propensity scores for admission to acute geriatric units and stratified seniors into quintiles according to scores sorted in ascending order. We performed logistic regression and propensity score matching (PSM) to estimate treatment effects for all seniors and for those within quintiles. Finally, we explored distribution of explanatory variables across quintiles.
Result: The 30-day mortality for 3034 seniors included for analyses was 25.8%. There was a significant reduction in 30-day mortality for senior admitted to acute geriatric units (adjusted OR 0.77; 95%CI 0.60 to 0.99) using logistic regression analyses. The following table shows 30-day mortality and selected patient characteristics across quintiles.
|Quintile 1 (n=607)||Quintile 2 (n=607)||Quintile 3 (n=606)||Quintile 4 (n=607)||Quintile 5 (n=607)|
|Acute geriatric units: OR (95% CI)||0.82 (0.35-1.91)||1.16 (0.53-2.55)||0.97 (0.60-1.59)||0.66 (0.40-1.11)||0.57 (0.36-0.90)|
|Hospitalization in prior 90 days||28.2%||24.7%||23.6%||36.1%||36.6%|
Conclusion: Acute geriatric units reduced short-term mortality among seniors hospitalized for pneumonia, when compared with usual internal medicine care. Seniors who were more likely to receive care at these units had greater mortality reduction. These findings have implications on targeting policies for these and similar units including acute care for elders (ACE) units.
Purpose: To develop a clinical decision support tool to assist physicians with atrial fibrillation therapy design for primary prevention of stroke.
Method: The long-term antithrombotic therapy with warfarin reduces the relative risk of stroke from atrial fibrillation by approximately 65%, while increasing the bleeding risk. Aspirin constitutes a less aggressive therapy option with lesser impact on the stroke and bleeding risks. Given the potential benefits and risks of these options, and recognizing each patient's case-mix and clinical variables, the therapy choice decisions are critical. We formulate the problem as a Markov Decision Process (MDP) so as to maximize the patient's expected remaining QALY (i.e., quality-adjusted life years). The decision alternatives at each time epoch are warfarin, aspirin and “no medication”. The risk score and the bleeding score of the patient are the state variables of the MDP. The former is estimated using the CHADS scale, and the latter is accessed via the Beyth framework. The MDP transition probabilities are estimated using charts of the 950+ atrial fibrillation patients from the anticoagulant clinic of Montreal Jewish General Hospital.
Result: Using the MDP model, we identified the optimal therapy choice based on the patient's age, stroke score (s) and bleeding score (b). The Table below depicts our results. For example, our framework suggests that an 85 year old patient with s=1 and b=1 should be started on Warfarin (W), whereas if the patient was a year older with the same risk factor Aspirin (A) would be the better choice. We estimated the expected remaining QALY of the 950+ patients by the use of our methodology. Comparing the results with the patient files showed that significant improvements in may be achieved. Especially, for the younger group of patients with moderate stroke risk (with stroke score 1 or 2) and high bleeding risk (with bleeding score 2 and 3), these potential improvements varied between 16% and 37%.
Conclusion: The current clinical guidelines for atrial fibrillation therapy are based on only the stroke risk of the patient. Our research shows that it is possible to improve the health outcomes by also incorporating the patient's bleeding risk in the decision process.
Purpose: Childhood obesity threatens the future health of America's adults. Recently, the U.S. Preventive Services Task Force recommended childhood obesity screening to better target preventive interventions. Others advocate universal childhood interventions. Projections of the impact of childhood obesity on future adult health are needed to guide policy decisions.
Method: We developed the Stanford Childhood Obesity Projection and Evaluation (SCOPE) model to simulate body mass index (BMI) dynamics for children starting at age 2. The SCOPE model follows children as they grow into adulthood, tracking their BMI and obesity status. The SCOPE model projects outcomes including BMI at ages 18 and 40, and diabetes and hypertension prevalence at age 40. The parameters of the SCOPE model were informed by nationally representative, longitudinal data: the National Health and Nutrition Examination Survey (NHANES 2006), National Longitudinal Survey of Youth (NLSY) Children and Young Adult samples; and Panel Study of Income Dynamics (PSID). Using the SCOPE model, we evaluated the following strategies: childhood obesity screening (at age 5, 10, or 15) with interventions for children at risk; and universal school-based obesity interventions (e.g., interventions such as Planet Health).
Result: Without intervention, 33% of U.S. children currently aged 5 through 10 will be overweight (BMI 25-30) or obese (BMI ≥30) by age 18. For obese 18 year-olds, the probability at age 40 of being obese is 70%, of being diabetic is 23%, and of being hypertensive is 39%. By contrast, for thin (BMI <25) 18 year-olds, the probability of being obese is 24%, of being diabetic is 1%, and of being hypertensive is 22%. Obesity screening in children under 10 misses more than 40% of those who become obese 18-year olds. Screening at age 15 misses less than 15%. Universal school-based interventions have greater health benefits than screening-guided interventions, reducing the number of 40 year-olds with BMI ≥30, diabetes, and hypertensions by as much as 1,000,000, 200,000, and 500,000, respectively.
Conclusion: Results from the SCOPE model support the role of universal school-based interventions as promising tools to address adult obesity-related illness compared to childhood obesity screening. If universal interventions are infeasible, targeting obesity screening in early teen years has a greater potential benefit than screening for young children. Such interventions complement the continued importance of obesity interventions during adulthood.
Purpose: Sugar-sweetened beverages (SSB) are an important source of excess calories among U.S. adults and have been linked to both obesity and diabetes. Previous studies predicted that a one-penny-per ounce excise tax on these beverages would reduce consumption by 10-20%.This study aims to quantify the potential impact of such tax on diabetes, cardiovascular disease, and medical costs.
Method: We predicted the downward shift in SSB consumption from the baseline levels reported in the National Health and Nutrition Examination Survey 2003-2006 as a result of the tax, as well as the associated reduction in energy intake (adjusted for compensatory changes in other beverages), body weight, and risk of diabetes. We subsequently used the Coronary Heart Disease (CHD) Policy Model, a Markov cohort simulation model, to project the downstream burden that could be avoided from such tax scenario, quantified by the number of CHD and stroke events avoided and associated medical costs saved among US adults 25-64 years of age over 10 years.
Result: We predicted a reduction in average weight by 0.6-1.1 lbs and mean BMI by 0.2-0.4 kg/m2 as a result of 10-20% reduction in SSB consumption and a net daily energy reduction of 6-12 kcal/day per person. The projected reduction was greater in persons aged <45 years and in men, mostly due to their higher baseline SSB consumption. Over the course of 10 years, this downward shift in consumption and BMI can potentially result in 1.9-3.2 million fewer adults who are obese, 1.5-2.5 million fewer type II diabetes person-years, averting 114,000-223,000 cases of CHD events and 10,000-20,000 fewer cases of stroke, and saving $78-129 billion (in 2010 dollars, discounted by 3% annually) in medical expenditure from cardiovascular disease and diabetes treatment.
Conclusion: In addition to generating approximately $15 billion a year in revenue, taxes on sweetened beverages would potentially reduce the health and economic burden of obesity, diabetes, and cardiovascular diseases among U.S. adults.
Purpose: A general societal preference for prioritizing treatment of rare diseases over common ones could provide a justification for accepting higher cost-effectiveness thresholds for orphan drugs. We attempt to determine whether such a preference exists.
Method: We surveyed a random sample of 1547 Norwegians aged 40-67. Respondents chose between funding treatment for a rare versus common disease and completed a person trade-off (PTO) exercise between the diseases for each of two scenarios: (1) identical per person costs, and (2) higher costs for the rare disease. Diseases were described identically with the exception of prevalence. Respondents were randomized to either no information or different amounts of information about disease severity (severe vs. moderate) and expected benefits of treatment (high vs. low). All respondents rated five statements concerning equity attitudes on a Likert-scale.
Result: 68% of respondents agreed completely with the statement “rare disease patients should have equal right to treatment regardless of costs”. Faced with trade-offs, 11.3% of respondents favored treating the rare disease, 24.9% the common disease and 64.8% expressed indifference. When the rare disease entailed a higher opportunity cost, results were 7.4%, 45.3% and 47.3%, respectively. Framing (“extra funding” vs. “fixed budget”) and amount of information about severity and treatment effectiveness had a small impact on preferences.
Conclusion: Although there is strong support for general statements expressing a desire for equal treatment rights for rare disease patients, that support evaporates when individuals are faced with opportunity costs.
Purpose: Transmission dynamic models have been used over the years for assessing the health and economic impact of interventions to control the spread of infectious diseases. Given the growing requirements to use probabilistic sensitivity analysis (PSA) to provide a single, global analysis of uncertainty in input parameters, use of PSA is hampered by the inherent complexity of these dynamic models. The objective of this study is to assess the feasibility of conducting PSA in a complex dynamic model by using HPV vaccination of boys and men in the United States as an example.
Method: We used previously developed age-structured mathematical population models of HPV vaccination. All 14 models consist of a series of nonlinear ordinary differential equations. Inputs for the models were obtained from public data sources, published literature, and analyses of clinical trial data. Inputs related to vaccine properties and uptake, cost, and quality of life weights were included in a PSA. Latin hypercube sampling techniques were used to generate 200 random samples. These were used as inputs in the simulations carried out in Mathematica. The uncertainty in the results was summarized in cost-effectiveness acceptability curves, and most influential parameters were determined using the partial rank correlation coefficient.
Result: We succeeded in performing the simulation of all models separately, calculating several measures of vaccine impact, and combining the results for cost-effectiveness analysis. For example, we found that compared with a program of vaccinating girls and women only, including boys and men has potentially substantial public health and economic benefits. The mean cost-effectiveness ratio of this strategy was $25,700 (Range: 13,600–48,800) per QALY gained, signifying cost effectiveness at the commonly cited thresholds. Influential parameters include vaccine cost, efficacy of only two doses, compliance, degree and duration of protection, quality of life of men with genital warts, and uptake among girls and women. However despite the ability to generate these findings, the amount of time needed to complete the 200 runs for a single model could be up to 17 hours depending on the complexity of individual models.
Conclusion: Although this study demonstrated the feasibility of conducting PSA in complex dynamic models, use of PSA may still be hampered with more complex models and/or a need to generate greater sets of runs (e.g., n=1,000).