Three Essays on Health Economics

This dissertation consists of three essays on health economics. The first chapter evaluates the impacts of and behavioral responses to cost-sharing in population-based public cancer screening using Korea's National Cancer Screening Program (NCSP), which provides free stomach and breast cancer screenings to those below the insurance contribution cutoff. Free cancer screening substantially increases the cancer screening take up rate, yielding more cancer detections. Nevertheless, the program was unsuccessful along other key dimensions. First, the initial increase in cancer detections was quickly crowded out by the decrease in cancer detections through other channels, such as private screening and diagnostic testing. Second, those who were induced to take up cancer screening by the cash incentive (compliers) were relatively healthy. These compliers' baseline cancer prevalence is as high as those who take up screening regardless of the availability of free cancer screening (always takers). Those who do not undergo screening regardless of the availability of free cancer screening (never takers) had the highest cancer mortalities, and thus stood to benefit the most from the screening they did not receive. Taken together, free public cancer screening has a limited impact on cancer- and all-cause mortalities. This analysis demonstrates that even when take up is significantly responsive, population based cancer screening can be ineffective due to the behavioral responses to cancer screening such as crowd out and self-selection. More broadly, my study suggests that the impact of health programs, even when they display large participation responses, crucially depend upon the potential behavioral responses of the agents involved. The second chapter provides empirical evidence on the impacts of government reimbursement of long-term care. We apply a regression discontinuity design using administrative data from South Korea to estimate the impact of subsidies for formal home and institutional care on informal care use and medical expenditures. These subsidies lead to increases in formal long-term care utilization, even accounting for crowd out of private spending. Our main finding is that the benefits of home and facility care are heterogeneous across physical function level and therefore setting policy accordingly has the potential to dramatically reduce medical expenses. We also find that formal long-term care is not a strong substitute for informal long-term care at the extensive margin. Specifically, among individuals who are partially dependent for some activities of daily living (ADLs), we find that increased use of formal home care has no impact on the use of informal care at the extensive margin or on medical expenses. Among individuals who are partially dependent for several ADLs, we find that increased use of institutional care leads to reductions in informal care and medical expenses. From a policy perspective, these results suggest that publicly financed long-term care may have limited impact among the more able, and that home care may be both more cost effective and beneficial than institutional care for the least able. The third chapter provides empirical evidence on both outcomes and potential mechanisms resulting from information obtained from health screening. We apply a regression discontinuity design using administrative data from South Korea to estimate the impact of different classifications of overall health that vary discontinuously with blood sugar level. We find that "disease suspected" classification leads to increase clinic visit for the secondary examinations and future screening take-ups, and decrease of outpatient days and medical expenditure, however few impacts on health outcomes such as future blood sugar level and mortality. We also find that the responsiveness to the classifications among the highest income quintiles is lower than among the other quintiles, consistent with more educated individuals incorporating information directly from the blood sugar measure itself

Study of ocular transport of drugs released from a sustained release device

Delivering ocular therapeutics to a target site with minimal side effects requires detailed information about the distribution and elimination pathways. This knowledge can guide the development of new drug delivery devices. In this study, we investigated the movement of two drug surrogates, H-110, which is lipophilic, and Gd-DTPA, which is hydrophilic, released from polymer-based implants using a fluorescein technique and magnetic resonance imaging (MRI). We also studied the pharmacokinetics of intravitreally injected triamcinolone acetonide, a low water soluble drug used for treating sight-threatening diseases such as diabetic retinopathy and choroidal neovascularization associated with age-related macular degeneration (AMD). At 24 hour post implantation, H-110 released from an intravitreal implant was detected in the subretinal space. However, following a subconjunctival implant, very little H-110 fluorescence was detected in the subretinal region. H-110 most likely reached the subretinal space from an intravitreal implant by diffusion through the vitreous and retina. However, most of the H-110 released from a subconjunctival implant is thought to dissipate through the choroidal blood flow. Concentration profiles of Gd-DTPA, which was released from an intravitreal implant in a New Zealand white rabbit, approached pseudo-steady state within 7 to 8 hours and showed gradients at the rabbit's vitreous-retina border suggesting that diffusion was occurring into the retinal-choroidal-scleral membrane. Parametric analysis with a finite element mathematical model of the rabbit eye yielded for Gd-DTPA a diffusion coefficient of 2.8 × 10-6 cm2/sec in the vitreous and a permeability of 1.0 × 10-5 cm/sec in the composite retina-choroid-sclera membrane. Gd-DTPA concentration decreased away from the implant. Such regional concentration variations throughout the vitreous may have clinical significance when the ubiquitous eye diseases are treated using a single positional implant. Subconjunctival implants in vivo delivered a mean total of 2.7 µg of Gd-DTPA over 8 hours into the vitreous representing only 0.12% of the total amount of compound released from the implant in vitro. No Gd-DTPA was detected in the posterior segment of the eye. Ex vivo, the Gd-DTPA concentration in the vitreous was 30 fold higher suggesting the elimination of significant in vivo barriers to the movement of drugs from the subconjunctival space into the vitreous. We developed a new preservative-free formulation for intravitreal injections of triamcinolone acetonide for the treatment of diabetic macular edema, and choroidal neovascularization associated with AMD in human clinical trials at the National Institutes of Health. A pharmacokinetic study in rabbits was done to estimate elimination rate of two injection amounts of triamcinolone acetonide, 4 mg and 16 mg, from the vitreous. From our pharmacokinetic model, we found the half-lives for 4 mg and 16 mg injection in the vitreous to be 18.6 days and 37.6 days, respectively. We subsequently estimated the half-lives of 1 mg and 8 mg triamcinolone acetonide injection in order to predict therapeutic exposure in human. There are three components in this thesis: the study of lipophilic H-110 transport with fluorescence, the study of hydrophilic transport of Gd-DTPA with MRI, and the pharmacokinetic analysis of triamcinolone acetonide. They have each contributed to further insights into our fundamental understanding of drug movement in the eye and the implication on optimal therapeutic delivery

Knowing Is Not Half the Battle: Impacts of the National Health Screening Program in Korea

Health screening provides information on disease risk and diagnosis, but whether this promotes health is unclear. We estimate the impacts of the National Health Screening Program in Korea for diabetes, obesity, and hyperlipidemia. In this setting, information on disease risk and prompting for a secondary examination vary at different biomarker thresholds. We find evidence for increased diabetes medication and weight loss around the high risk threshold for diabetes, where information is combined with prompting for a secondary examination and subsequent medical treatment. However, we find no differences around other thresholds, where information is not combined with further intervention

Low-Rank Representation-Based Object Tracking Using Multitask Feature Learning with Joint Sparsity

We address object tracking problem as a multitask feature learning process based on low-rank representation of features with joint sparsity. We first select features with low-rank representation within a number of initial frames to obtain subspace basis. Next, the features represented by the low-rank and sparse property are learned using a modified joint sparsity-based multitask feature learning framework. Both the features and sparse errors are then optimally updated using a novel incremental alternating direction method. The low-rank minimization problem for learning multitask features can be achieved by a few sequences of efficient closed form update process. Since the proposed method attempts to perform the feature learning problem in both multitask and low-rank manner, it can not only reduce the dimension but also improve the tracking performance without drift. Experimental results demonstrate that the proposed method outperforms existing state-of-the-art tracking methods for tracking objects in challenging image sequences

The selection and causal effects of work incentives on labor productivity: Evidence from a two stage randomized controlled trial in Malawi

Incentives are essential to promote labor productivity. We implemented a two-stage field experiment to measure effects of career and wage incentives on productivity through self-selection and causal effect channels. First, workers were hired with either career or wage incentives. After employment, a random half of workers with career incentives received wage incentives and a random half of workers with wage incentives received career incentives. We find that career incentives attract higher-performing workers than wage incentives but do not increase productivity for existing workers. Instead, wage incentives increase productivity for existing workers. Observable characteristics are limited in explaining the selection effect

A Host Protection Framework Against Unauthorized Access for Ensuring Network Survivability

Abstract. Currently, the major focus on the network security is securing individual components as well as preventing unauthorized access to network services. Ironically, Address Resolution Protocol (ARP) poisoning and spoofing techniques can be used to prohibit unauthorized network access and resource modifications. The protecting ARP which relies on hosts caching reply messages can be the primary method in obstructing the misuse of the network. This paper proposes a network service access control framework, which provides a comprehensive, hostby-host perspective on IP (Internet Protocol) over Ethernet networks security. We will also show how this framework can be applied to network elements including detecting, correcting, and preventing security vulnerabilities