# Angela Man-Wei Cheung

Professor of Medicine, University of Toronto
Tier 1 Canada Research Chair in Musculoskeletal and Postmenopausal Health

Dissertation Title:  "The Economic Impact of Primary Prevention: Methods and Applications of Cost-Effectiveness Analysis"

This thesis examined the methodologies and applications of cost-effectiveness analyses in primary prevention. It is presented in the form of three papers. The first paper examined the lipid-mediated cardioprotective effects of long-term hormone replacement therapy in postmenopausal women using lipid profile changes observed in the PEPI trial, a multicenter randomized controlled trial of various hormone regimens. Our results showed that the lipid-mediated effects of long-term treatment with various hormone regimens in a 50 year-old postmenopausal woman yield average coronary risk reductions of 12-18%, and average gains in life expectancy of 0.19-0.28 years.

The second paper examined the cost-effectiveness of long-term hormone replacement therapy in postmenopausal women. This paper used age-specific incidences of coronary heart disease, breast cancer and hip fractures, and evaluated the balance of the costs and the effects of these diseases in postmenopausal women of different ages. The results of the first paper were used to set the most conservative estimate for the effect of hormone replacement therapy on coronary heart disease. We found that the cost-effectiveness ratio for long-term unopposed estrogen replacement therapy is $27,800 per year of life gained for 50 year-old women without a uterus (discounted at 3% and expressed in 1996 US dollars), and$42,200 for long-term combination therapy for 50 year-old women with a uterus. In general, the cost-effectiveness ratios of long-term hormone replacement therapy for older postmenopausal women are more attractive than for younger postmenopausal women.

The third paper examined the cost-effectiveness of blood pressure screening in children. We used longitudinal tracking correlations to predict adult blood pressures from childhood blood pressures, and modeled the effects and costs of various screening and intervention strategies. We found that blood pressure screening strategies for 15 year-old children are more cost-effective than population-wide interventions ($76,000-$131,000 compared with $120,000-$187,000 per discounted year of life gained for boys, and $120,000-$216,000 compared with $212,000-$330,000 per discounted year of life gained for girls). In general, boys have lower (more attractive) cost-effectiveness ratios than girls. Overall, when compared to no screening or intervention, the most cost-effective strategy for the control of blood pressure is screening plus dietary sodium reduction for those who are hypertensive ($76,000 and$120,000 per discounted year of life gained for boys and girls, respectively.) However, neither blood pressure screening nor population-wide interventions are very cost-effective.