Social Analysis 76/PBHL E-100 Midterm Review

1. Social Analysis 76/PBHL E-100 Midterm Review Presenters: Chara Jhumka Katy Iris Harvard University Initiative for Global Health

2. Outline Section 1 • Incidence vs. Prevalence • Sensitivity vs. Specificity • Domains of Health Section 2 • Demographic and Epidemiologic Transition • Global Burden of Disease/DALYs • Health Inequalities • Income and Health • Dual Causality Section 3 • Drivers of health • Brief review of HIV disease, prevention and treatment strategies • Global response to HIV and emerging challenges Section 4 • Tuberculosis • Malaria Harvard University Initiative for Global Health

3. Prevalence Prevalence - The proportion of a population that exists with the disease at a given point in time. Prevalence =Number of individuals with disease Population • Ranges from 0-1 or 0-100%, and can be interpreted as the probability that an individual will have a disease at a given point in time. • The population here is considered to be the disease and disease free populations (total population). • Note that prevalence is not a rate. Harvard University Initiative for Global Health

4. Incidence Incidence – The development of a disease among those who are at baseline free of disease, over a given time period. Incidence =Number of new cases of a disease Person-time of observation • Here the population at risk is only the disease free people. • Incidence is a rate, not a proportion, so the time period matters. • Usually time is measured in person-time observation. Harvard University Initiative for Global Health

5. An Example • 100 women were screened for Disease X. 10 women were found to have Disease X at the initial examination. The remaining women were followed for 3 years, with a total of 30 women dying by the end. 10 women died each year. • What’s the Prevalence of Disease X? Harvard University Initiative for Global Health

6. Answer • Prevalence= 10/100 =0.1 Harvard University Initiative for Global Health

7. Example 2 • What about incidence of death from Disease X from year 1 to year 2? • Do a mid-year calculation • Incidence =10/((100+90)/2) Harvard University Initiative for Global Health

8. Sensitivity and Specificity There are almost no perfect tests, meaning that almost any test result will be subject to some sort of error. By understanding the specificity and sensitivity of a test, we are able to get a better understanding of our test results. • Sensitivity – The proportion of those people with the disease who will test positive. • Specificity – The proportion of the people without the disease who will test negative. Harvard University Initiative for Global Health

9. 2X2 Table Sensitivity= A/(A+B) =10/30 =0.33 Specificity= D/(D+C) =130/270 =0.48 Harvard University Initiative for Global Health

10. 2X2 Table Can you fill in all the boxes? What information do you need? Sensitivity=0.33 Specificity=0.48 Prevalence=? Total Population Tested = 300 Total testing positive = 150 True prevalence: p(sensitivity) + (1-p)(1-specificity)= percent testing positive p(.33)+ (1-p) (1-0.48)=150/300 p= 0.10 Harvard University Initiative for Global Health

11. Domains of health Harvard University Initiative for Global Health

12. Domains of health • Direct domains of health: Nearly universally accepted, restricted set of domains chosen because a decrement in one could lead to bad health. However, people can legitimately make the claim that other direct measures of health should be included. • Indirect domains of health: Less universally accepted and more variable, but are seen by many as impacting health. Harvard University Initiative for Global Health

13. Outline Section 1 • Incidence vs. Prevalence • Sensitivity vs. Specificity • Domains of Health Section 2 • Demographic and Epidemiologic Transition • Global Burden of Disease/DALYs • Health Inequalities • Income and Health • Dual Causality Section 3 • Drivers of health • Brief review of HIV disease, prevention and treatment strategies • Global response to HIV and emerging challenges Section 4 • Tuberculosis • Malaria Harvard University Initiative for Global Health

14. Demographic Transition • Definition: term used to describe the developed country transition from: High Mortality Rates Low Mortality Rates High Fertility Rates Low Fertility Rates • Implication: Shift leads to change in age structure of populations Harvard University Initiative for Global Health

15. No transition Post transition Harvard University Initiative for Global Health

16. Epidemiologic Transition • Communicable diseases decrease • Non-communicable diseases increase • Linked to shift in age structure due to demographic transition • Consider situations when this pattern does not hold. Harvard University Initiative for Global Health

17. Global Burden of Disease (GBD) • What is disease burden? • Gap b/w a population’s actual health status and some ideal/reference status • Mortality does not capture disease status while a person is alive • Implications for resource allocation • DALYs are a better measure of GBD Harvard University Initiative for Global Health

18. DALYs • DALY = YLL + YLD • YLL = years of life lost to premature death • YLD = years lived w/ a disability of specified severity and duration • 1 DALY = 1 year of healthy life lost • Premature death = occurs before age to which the dying person would have expected to live if they were a member of the standardized population. Harvard University Initiative for Global Health

19. Why are DALYs useful? • Compare the health of one population with another • Analyze the benefits of health interventions for use in cost-effectiveness analysis • Identify and quantify overall health inequalities within populations • Informing debates on health policy • Monitor changes in health in a given population • Key to GBD study Harvard University Initiative for Global Health

20. DALY Value Choices • Assumes standard life table for all populations • Age-weighting: peaks in early twenties • Age discounting-future healthy life is valued less than healthy present life Harvard University Initiative for Global Health

21. Health Inequalities • Inequality-no normative judgment • Inequity-invokes the concept of social justice; normative judgment • Absolute/Relative inequality • Must consider both!!! Harvard University Initiative for Global Health

22. Outline Section 1 • Incidence vs. Prevalence • Sensitivity vs. Specificity • Domains of Health Section 2 • Demographic and Epidemiologic Transition • Global Burden of Disease/DALYs • Health Inequalities • Income and Health • Dual Causality Section 3 • Drivers of health • Brief review of HIV disease, prevention and treatment strategies • Global response to HIV and emerging challenges Section 4 • Tuberculosis • Malaria Harvard University Initiative for Global Health

23. Drivers of Health: causal pathways

24. Health outcomes (disease, injury, functional impairment, death) • Causal factors • Societal factors (political, economic, cultural) • Individual attributes (edu, income, prefs) • Behaviors and practices (behavioral risk factors) • Physiological factors (biological risk factors) • Health system • Physical environment Harvard University Initiative for Global Health

25. But how is this related to that other diagram? Harvard University Initiative for Global Health

26. Drivers of Health • Education (especially maternal education) • Consistent relationship between increased maternal education and better child health • WHY? • Exposure to health information (school, media, etc) • Health seeking behaviors • Empowerment in HH decisionmaking • Changes in fertility, labor force participation Harvard University Initiative for Global Health

27. Drivers of Health • Income • Rising per capita income leads to better • Nutrition, housing sanitation, health services • Technology • Role as a driver of health (Preston curve) • Challenges to scale up • Lag between development and widespread use Harvard University Initiative for Global Health

28. Drivers of Health • Preston’s analysis of mortality decline (1960s and 1970s) • Income • Literacy • Nutrition • Past experience vs. future trends Harvard University Initiative for Global Health

29. HIV Disease Harvard University Initiative for Global Health

30. Measuring HIV/AIDS • Methods: ANC surveillance, surveys • Problems with using ANC surveillance data • Overestimate of HIV prevalence (women at clinics have higher prevalence, on average, than the whole population) • Most surveillance data is based on urban areas • Women at ANC are sexually active • Surveillance data is biased towards younger ages because young women are more likely to get pregnant Harvard University Initiative for Global Health

31. HIV Transmission Modes of transmission • sexual contact • blood contact (IV drug use, unsafe healthcare injections, unsafe blood transfusions) • mother to child transmission Probability of transmission • average prob of trans per coital act = 0.1% • annual prob of trans for discordant couples = 10.2% • mother to child transmission without intervention = 30% • Influencing factors: viral load, type of sex (anal, vaginal, oral); presence of ulcerative STIs, male circumcision Harvard University Initiative for Global Health

32. HIV Prevention • Strategies • Decrease the number of risky sex acts (change behavior) • Abstinence, delay sex, decrease # of partners • Decrease the probability of transmission per sex act • Treat STDs, condom use, male circumcision (?) • Decrease MTCT • Lots of debate • Future: vaccines, microbicides Harvard University Initiative for Global Health

33. HIV Treatment: ARVs/HAART • Impacts • dramatic effect on improving AIDS survival at individual level (P. Farmer’s patient), • decrease in probability of developing AIDS, decrease in probability of death in US, Europe (Egger, Lancet article) • Considerations • triple drug therapy does not cure the disease • a person must stay on the drugs even if they are asymptomatic - chronic lifetime intervention Harvard University Initiative for Global Health

34. Treatment vs. Prevention • Common debate about balance between treatment and prevention • Most people agree that a mixture is best • Issues that arise: • Cost • Sustainability • Behavior change • Ethics Harvard University Initiative for Global Health

35. Outline Section 1 • Incidence vs. Prevalence • Sensitivity vs. Specificity • Domains of Health Section 2 • Demographic and Epidemiologic Transition • Global Burden of Disease/DALYs • Health Inequalities • Income and Health • Dual Causality Section 3 • Drivers of health • Brief review of HIV disease, prevention and treatment strategies • Global response to HIV and emerging challenges Section 4 • Tuberculosis • Malaria Harvard University Initiative for Global Health

36. Tuberculosis Mycobacterium tuberculosis Transmission through the air – not behavior Pulmonary versus extrapulmonary TB HIV is changing risk of breakdown, case fatality, and transmission Latent infection versus active disease time since infection, age, and host immunity Drug susceptible versus drug resistant TB TB has a long memory – difficult to estimate incidence Harvard University Initiative for Global Health

37. Diagnosis Two types of pulmonary clinical disease: sputum-smear positive (more infectious) and sputum culture positive. Diagnosis Chest x-ray Pulmonary sputum smear Pulmonary sputum culture PPD skin test New interferon-γ blood test, more specific Harvard University Initiative for Global Health

38. 8.9 Million Cases 1.6 Million Deaths Harvard University Initiative for Global Health

39. Preventive Interventions • Decreasing probability of transmission: UV lights, negative air-pressure rooms, isolation • BCG Vaccination – prevents childhood extrapulmonary tuberculosis, indeterminate efficacy for adult pulmonary tuberculosis. • Chemoprophylaxis or preventive therapy for 2-6 months decreases breakdown by 60-80%. • Detection and treatment of smear positive cases reduces the risk of transmission. Harvard University Initiative for Global Health

40. Standard Treatments WHO standard drug regimen uses 4 drugs for 2 months and then 2 drugs for 4 months. If completed, 90+% cure rate. Key issue is adherence to 6 months of therapy. WHO since 1994 recommends DOTS: Directly Observed Therapy, Short-Course Drug regimens for MDR-TB are longer and more expensive. Harvard University Initiative for Global Health

41. Control (1) Before the advent of effective drugs, tuberculosis incidence was declining for 50 years in high-income countries. DOTS – passive case finding Individuals with symptoms go to the clinic Improving sputum microscopy will raise case detection Raising cure rates through DOTS Harvard University Initiative for Global Health

42. WHO Global Tuberculosis Report 2006 Harvard University Initiative for Global Health

43. Some Criticisms of DOTS Strategy • MDR-TB is being neglected. • Tuberculosis incidence continues to rise in communities with high HIV sero-prevalence. • Insisting on direct observation of therapy is not necessary and distracts from other efforts to increase case-detection. • Preventive therapy is being ignored. • Case-detection rates cannot be increased over 45% without addressing fundamental health system issues. Harvard University Initiative for Global Health

44. Human Malaria There are four types of human malaria falciparum, vivax, ovale, malariae, first two cause most human disease Malaria is a disease that requires the presence of a vector which in this case is the anopheline mosquito. Transmission happens at night The severity of the attack is determined by the species and the strain, on age, genetic constitution, immunity, general health, nutritional status and use of antimalarial drugs Harvard University Initiative for Global Health

45. Harvard University Initiative for Global Health

46. Malaria Diagnosis Thick and thin smears of blood can be used to detect Plasmodium. In developing countries, most malaria is diagnosed presumptively on the basis of fever and symptoms. False positives are common because in some endemic areas more than 50% of adults have parasites. Harvard University Initiative for Global Health

47. Epidemic Malaria The focus of most of is on malaria in endemic communities, endemic meaning where there is regular transmission each year. In some communities, malaria transmission may occur under unusual environmental circumstances (heavy rains) and inmigration of infected individuals. Individuals in these communities have not acquired immunity and are at high risk of severe malaria. Preventing the malaria epidemics requires surveillance and appropriate vector control and prophylactic interventions. Harvard University Initiative for Global Health

48. Most of the malaria burden is from deaths in young children Harvard University Initiative for Global Health

49. Acquired Immunity Natural exposure to P falciparum gradually elicits, in human hosts, short-lived strain-specific malaria immunity: first to severe disease and death, and then to mild disease. Repeated infections are required to maintain immunity, which is both antibody and T-cell based. Acquisition of immunity in endemic areas explains why clinical episodes are often more severe in children in these communities. Impact of all intervention strategies requires long-term consideration of the consequences for acquired immunity. Harvard University Initiative for Global Health

50. Prevention Vector control – DDT use recommended again ITNs – also vector control Prophylaxis for children - some fear may lead to increased mortality at older ages due to decreased acquired immunity. Prophylaxis forpregnant women –reduced incidence of severe anaemia and reduced low birth weight. Prophylaxis forTravellers Management of Malaria epidemics Harvard University Initiative for Global Health