Assessing the Cost-Effectiveness of Interventions for Cardiovascular Disease Prevention in Thailand

Panrasri Khonputsa (2010). Assessing the Cost-Effectiveness of Interventions for Cardiovascular Disease Prevention in Thailand PhD Thesis, School of Population Health, The University of Queensland.

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Author Panrasri Khonputsa
Thesis Title Assessing the Cost-Effectiveness of Interventions for Cardiovascular Disease Prevention in Thailand
School, Centre or Institute School of Population Health
Institution The University of Queensland
Publication date 2010-08
Thesis type PhD Thesis
Supervisor Dr. J Lennert Veerman
Dr. Melanie Bertram
Professor Theo Vos
Total pages 222
Total black and white pages 222
Subjects 11 Medical and Health Sciences
Abstract/Summary Background: Economic evaluation of interventions for disease prevention and treatment is increasingly popular worldwide due to the need to efficiently allocate limited health care resources. Cardiovascular disease (CVD) is a major health problem in Thailand. Aims: To provide the Thai healthcare system with information on ways to efficiently reduce CVD. Methods: The dissertation is composed of six parts. The first part involves literature search to convey an understanding of CVD epidemiology (incidence, prevalence, and mortality), and health and economic outcomes. General methods for assessing burden of disease and risk factors and economic evaluation are also presented. Although this thesis advocates the use of ‘absolute CVD risk assessment’ in favour of treatment by individual risk factors, the second chapter reports the joint prevalence, treatment and control, and factors associated with diagnosis, treatment and control of hypercholesterolemia and hypertension using data from a national health survey. This was done to gain an overview of both risk factors and their current treatment in Thailand before turning to the absolute risk approach. Chapter Three measures associations, in terms of relative risk (RR), of systolic blood pressure (SBP) and cholesterol (TC) with ischaemic heart disease (IHD) and stroke. RRs of IHD/stroke associated with 10 mmHg increase in SBP or 1 mmol/l increase in TC are assessed for 2,702 males and 797 females aged 35-54 at the start of study using Cox Proportional Hazards Models. The results are compared with those obtained elsewhere. Chapter Four presents the development of a tool for predicting CVD risks for Thai people. Framingham risk equations are recalibrated using contemporary cumulative risks of CVD. Using Thai population data, predictions of the recalibrated equations are compared with those generated with a published equation. Chapter Five assesses the cost-effectiveness of blood pressure (BP) and TC lowering drugs for CVD prevention in 6 population subgroups by sex and level of absolute CVD risk. A Markov model is developed with 4 explicit health states: alive without CVD, alive with IHD, alive with stroke and death. The comparator is doing nothing. Current practice is also assessed. Results: There is clear evidence for a causal link between CVD and several risk factors (such as suboptimal blood pressure (BP) and total cholesterol (TC), tobacco use, and diabetes mellitus), and a number of interventions have been proven effective against CVD. Reduction of TC and/or BP from any level is beneficial in reducing CVD incidence. The terms ‘hypertension’ or ‘hypercholesterolemia’ have become clinically less important than ‘absolute CVD risk’, which takes into account synergistic effects of multiple risk factors. Although the evidence comes mainly from developed countries, there is a trend towards greater risk factor exposure in many developing countries because of changes towards life styles with high fat consumption, low physical activity levels, and low vegetable and fruit consumption. Rises in CVD incidence in developing countries are likely (Chapter 1). In Thailand, 14% and 17% of men and women have hypercholesterolemia, 23% and 21% have hypertension, and 5% and 6% have both, respectively. A large proportion of individuals with these risk factors is not diagnosed nor treated, let alone adequately controlled (Chapter 2). Assessment of associations showed that each 1 mmol/L increase in TC is associated with a 5-fold increase in IHD risk in people aged 30-44. RRs of IHD/stroke per 10 mmHg increase in SBP are significant in all age groups. Increases in IHD and stroke risks associated with these 2 risk factors are comparable to those in the Asia Pacific and western populations (Chapter 3). In Chapter Four, average incidence of IHD in men and women aged 30+ is estimated at 480 and 500, and stroke, 840 and 720 per 100,000, respectively. Framingham equations before calibration overestimated IHD risks by 250% in men and 59% in women and stroke by 16% in men. Our equation produced similar predictions for CVD risks in Thai men over 8 years as the existing equation, but our equations can be used for predicting CVD risk at any time span and in both sexes. Assessment of the cost-effectiveness of BP and TC lowering drugs shows that the most cost-effective option for CVD prevention in people with 10-year risks of 5% and greater would be a generic ‘polypill’ (a theoretical tablet containing three BP lowering drugs (thiazide diuretics, calcium channel blockers, and angiotensin converting enzyme inhibitors) in half standard doses and a statin in standard dose) followed by a combination of the three generic BP drugs (in full doses). Current practice is much less cost-effective than these generic combinations. Conclusions: There is great scope for improved prevention of CVD in Thailand with regards to current levels and management of BP and TC and the use of effective generic drugs. Intensification of these interventions is strongly recommended. Cost-effectiveness of other population wide interventions such as the use of food condiments high in potassium and low in sodium and tobacco use cessation should be further investigated.
Keyword economic evaluation
cardiovascular disease
CVD prevention
resource allocation

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