Bruce Wang

Examining the BMI-mortality relationship using fractional polynomials

BackgroundMany previous studies estimating the relationship between body mass index (BMI) and mortality impose assumptions regarding the functional form for BMI and result in conflicting findings. This study investigated a flexible data driven modelling approach to determine the nonlinear and asymmetric functional form for BMI used to examine the relationship between mortality and obesity. This approach was then compared against other commonly used regression models.MethodsThis study used data from the National Health Interview Survey, between 1997 and 2000. Respondents were linked to the National Death Index with mortality follow-up through 2005. We estimated 5-year all-cause mortality for adults over age 18 using the logistic regression model adjusting for BMI, age and smoking status. All analyses were stratified by sex. The multivariable fractional polynomials (MFP) procedure was employed to determine the best fitting functional form for BMI and evaluated against the model that includes linear and quadratic terms for BMI and the model that groups BMI into standard weight status categories using a deviance difference test. Estimated BMI-mortality curves across models were then compared graphically.ResultsThe best fitting adjustment model contained the powers -1 and -2 for BMI. The relationship between 5-year mortality and BMI when estimated using the MFP approach exhibited a J-shaped pattern for women and a U-shaped pattern for men. A deviance difference test showed a statistically significant improvement in model fit compared to other BMI functions. We found important differences between the MFP model and other commonly used models with regard to the shape and nadir of the BMI-mortality curve and mortality estimates.ConclusionsThe MFP approach provides a robust alternative to categorization or conventional linear-quadratic models for BMI, which limit the number of curve shapes. The approach is potentially useful in estimating the relationship between the full spectrum of BMI values and other health outcomes, or costs.

Assessing the potential cost-effectiveness of retesting IHC0, IHC1+, or FISH-negative early stage breast cancer patients for HER2 status

Fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) tests are commonly used to assess human epidermal growth factor 2 (HER2) status of tumors in patients with breast cancer. This analysis evaluates the likely cost‐effectiveness of expanded retesting to assess HER2 tumor status in women with early stage breast cancer.

Modelling the long-term outcomes of bariatric surgery: A review of cost-effectiveness studies

Obesity, defined as BMI ≥30 kg/m(2), affects over 30% of the United States adult population and has been declared an epidemic by the Centers for Disease Control. Bariatric surgery is a treatment option to reduce excess weight and is available to individuals with BMI greater than 40 kg/m(2), or 35 kg/m(2) with obesity-related comorbidities. As surgical options have become more common, researchers have analysed the long-term cost-effectiveness of these procedures. However, the follow-up data on patients is limited, and modelers need to forecast lifetime costs and outcomes for this chronic disease. In this chapter, we conduct a systematic literature review of cost-effectiveness studies on bariatric surgery to understand the forecasting methods used in practice. We identified six unique studies, which used statistical models, Markov models, or assumptions to forecast lifetime outcomes. We discuss each of the approaches, so clinicians, policy-makers, and payers can make informed interpretations based on the models.

The short-term cost-effectiveness of once-daily liraglutide versus once-weekly exenatide for the treatment of type 2 diabetes mellitus in the United States.

Background Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease with substantial morbidity, mortality, and economic impacts. Glucagon-like peptide-1 (GLP-1) receptor agonists, such as once-daily (QD) liraglutide and once-weekly (QW) exenatide, are FDA-approved treatment for T2DM. Head-to-head trials and meta-analyses comparing these agents have reported clinically meaningful improvements but small differences in glycemic control between both agents. In this study, we calculate and compare the cost-effectiveness implications of these alternative effectiveness outcomes. Methods We developed a decision model to evaluate the short-term cost-effectiveness of exenatide QW 2 mg versus liraglutide QD 1.8 mg in T2DM patients, with effectiveness measured as reduction in glycated hemoglobin (HbA1c). In the base case, the model tracks change in HbA1c and direct medical expenditure over a 6-month time horizon. We calculated and compared the cost per 1% reduction in HbA1c of models populated with clinical data from a head-to-head randomized, controlled trial (DURATION-6) and a network meta-analysis. Expenditure inputs were derived from wholesale acquisition costs and published sources. Results In the base case, 6-month expenditure for the liraglutide and exenatide strategies were

BMI Trajectories Among the Severely Obese: Results From an Electronic Medical Record Population

3,509 and

The Lifetime Economic Burden of Inaccurate HER2 Testing: Estimating the Costs of False-Positive and False-Negative HER2 Test Results in US Patients with Early-Stage Breast Cancer

2,618, respectively. Using clinical data from DURATION-6 and the network meta-analysis, the liraglutide strategy had an incremental cost per 1% reduction in HbA1c of

Precision Health Economics and Outcomes Research to Support Precision Medicine: Big Data Meets Patient Heterogeneity on the Road to Value

4,773 and

Epidemiology of pharmaceutically treated depression and treatment resistant depression in Taiwan

27,179, respectively. The most influential model parameters were drug costs, magnitude of HbA1c reduction in patients on treatment for >1 month, and liraglutide gastrointestinal adverse event rate. In probabilistic sensitivity analyses (PSA) using DURATION-6 data, the exenatide strategy was optimal at willingness-to-pay levels below

Estimating the Economic Burden of Rheumatoid Arthritis in Taiwan Using the National Health Insurance Database

4,800 per 1% reduction in HbA1c. In a PSA using meta-analysis data, the exenatide strategy was dominant. Conclusions Our modeled results demonstrate that the effectiveness and cost-effectiveness of liraglutide QD 1.8 mg relative to exenatide QW 2 mg depend largely on the chosen source of the clinical data.

The cost reduction in hospitalization associated with paliperidone palmitate in the People’s Republic of China, Korea, and Malaysia

Epidemiological studies have documented the growing prevalence of severe obesity during the past three decades. The primary goal of this study was to estimate the trajectory of BMI change over 5+ years in a cohort of subjects identified as severely obese (BMI ≥35). We conducted a retrospective cohort study among adults enrolled in Group Health (GH) in Washington State. We tracked 11,735 subjects with at least one BMI measure of 35 or greater in the calendar year 2005 through April 2010. Population averaged BMI trajectories were estimated as a quadratic function of time using a marginal regression model, adjusting for gender and baseline BMI and age. For the average male in GH, the estimated BMI trajectory exhibited a slightly inverted U‐shaped pattern and a 0.17 increase in BMI over the sample period. For the average female, the BMI trajectory was slightly U‐shaped with BMI decreasing 0.03 units over the sample period. We found a high degree of heterogeneity in the shape of estimated trajectories across baseline characteristics with larger 5‐year BMI increases among younger subjects with a lower initial BMI. We conclude that BMI changes over 5 years among individuals classified as severely obese are generally small and consistent with studies documenting BMI changes for individuals in other lower BMI categories. Our results also suggest that once the 35 BMI threshold is reached, individuals will continue to remain severely obese, especially at younger ages.