Population and Public Health

1. Population and Public Health ENVRE 115 Oct. 9, 2007

2. Announcements • Send in student biographies • Assignment #2 due • Graduate Student Projects • Groups have been assigned • Encourage you to use discussion board to communicate with team mates • Require topic approval by Tues., Oct. 30th • Make appointment to meet with Molly

3. Agenda • Demographic Tools • Drivers of population growth • Development & Epidemiological Transition • Demographic Dividend

4. World population milestones

5. World Population Growth Through History 12 Billions 11 2100 10 Future? 9 Modern Age Old 8 Iron Middle Bronze Stone Age New Stone Age Ages Age Age 7 6 2000 5 4 1975 3 1950 2 1900 1 1800 Black Death — The Plague 2000 1+ million 7000 6000 5000 3000 1000 A.D. 4000 A.D. A.D. A.D. A.D. A.D. years B.C. B.C. B.C. B.C. B.C. B.C. B.C. 1 1000 2000 3000 4000 5000 Source: Population Reference Bureau; and United Nations, World Population Projections to 2100 (1998).

6. Trends in Worldwide Population Growth Population Increase and Growth Rate, Five-Year Periods Percent increase per year Millions Source: United Nations, World Population Prospects: The 2004 Revision (medium scenario), 2005.

7. Projected Growth in World Population UN Pop.Div(2004);WRI(2006) Earthtrends.wri.org

8. Introduction to Demographics Terminology Growth Rates Population Pyramids

9. Terminology • Count: The absolute number of a population occurring in a specific area in a specified time period. Provides raw data. • Census data (number of people in the US) • Rate: The frequency of demographic events in a population divided by the population “at risk” during the same time period. • Birth rates (number of live births/number of women of childbearing age) • Ratio: The relation of one population sub-group to the total population or to another subgroup. • Sex ratios (number of males/number of females) • Dependency ratio (# of under 15 + # of 65 and over/# of 15 to 64)

10. Census Data: Population in US

11. Growth RatesBirths/Total Population – Deaths/Total Population)*100 = Rate of Natural Increase • Examples of population growth rates (2003) • Belgium: 0.1% (10,318,000) • United Arab Emirates: 1.4% (3,800,000) • Uganda: 3% (25,632,794) • How long would take for these populations to double? • Belgium  700 years • United Arab Emirates  50 years • Uganda  23 years • The “Rule of 70” is used to calculate doubling time • Doubling Time = 70/rate expressed as a percentage • Assumption of constant growth rate during the time frame

12. Math Behind Exponential Growth • The basic differential equation for exponential growth: dN/dt = rN, over the period from t=0 to t = the time period in question, where N is the quantity growing and r is the growth rate • The integral of this equation is Nt = N0 x ert where N(t) is the size of a quantity after t intervals have elapsed, N(0) is the initial value of the quantity, e is the base of the natural logarithm, r is the average growth rate over the interval in question, and t is the number of intervals • If one knows the final and initial values of N and the average growth rate, one can find the time it takes at that average growth rate for the quantity to grow from its initial value to the final value t = ln [ N(t)/N(0) ] / r • A special case is the doubling time, which is the time when N(t)/N(0) = 2. At that point rt = ln 2 = 0.69. If one knows the growth rate as a decimal fraction, then the Doubling Time = 0.69 / r. • This can be further simplified…if the growth rate is given in percent, then 0.69 must be multiplied by 100, and the doubling time = 69/r. This can then be rounded up to 70 (which is why it is called the rule of 70)

13. Doubling Time Examples • Familiar example- compound interest on your bank account 1. How long would it take for your bank account to double when invested at 3.5% Time = 70/3.5 = 20 years 2. You invest $100 at 7% interest. How long will it take to have $200? Time = 70/7 = 10 years

14. Consider a country with 100 people, growing at 7% per year. In 10 years, the population will double to 200 people, in another 10 years it will double again to 400 people, etc (see graph) Doubling Time 3. How long will it take this country to reach 1 million? t = ln [N(t)/N(0)] / r t = ln (1,000,000/100)/0.07 t = ln (10,000)/0.07 t = 9.2103/0.07 t = 131.5 years

15. Doubling Time 4. In a country where the GDP is growing at 4.5% per annum and the population is growing at 1.0 % per annum, how long will it take for the per capita GDP to double? Doubling time = 70/(4.5%-1% ) = 70/3.5 = 20 years 5. In 1971, global population was 3.8 million and it is currently 6.8 million. What was the global population growth rate during this time frame? Time= 70/rate(%) 36 years = 70/rate rate = 70/36 rate= 1.9%

16. Crude and adjusted rates • Crude rates are affected by population characteristics, particularly age structure • Adjusted rates allow for valid comparisons • In 2002 Sweden’s crude death rate was 11 per 1,000 compared to Panama’s crude death rate of 5 per 1,000. Does this mean Panama has a lower mortality rate? No. Sweden has 18% of its population in the 65-year or older category where deaths are more likely to occur compared to Panama where 6% of its population are 65+.

17. Population PyramidsWhat can they tell us? • Graphically displays a population’s age and sex composition • Horizontal bars present the numbers or proportions of males and females in each age group. • The sum of all the age-sex groups in the population pyramid equals 100 percent of the population

18. What can we infer from this data?

19. Japan1995 Census

20. Drivers of Population Growth Birth Rate/Fertility Age structure of population Mortality

21. 1. Birth Rate • Birth rate is defined as the number of live births per 1,000 women aged 15-49 in a given year • Replacement level fertility • Net reproduction rate of 1 • Every woman of childbearing age has 1 daughter • Total fertility rate of 2.1 • Every woman of childbearing age has 2.1 children

22. Fertility Rates Are Declining Average number of children per woman Source: United Nations, World Population Prospects: The 2004 Revision, 2005.

23. Four factors that influence fertility • The proportion of women of childbearing age who are married or in a sexual union • The percent of women using contraception and the level of abortion • The proportion of women of childbearing age who currently are unable to conceive a child (usually from postpartum infecundity from breastfeeding) • Educational attainment of girls and women

24. Age at Marriage Median Age at First Marriage, Women 20 to 24 at Time of Survey Years Source: Measure DHS STATcompiler: accessed online at www.statcompiler.com on June 2, 2006.

25. Trends in Contraceptive Prevalence% of women in union aged 15-49 who are using contraception Sources:  UN Population Division database, data available as of 1 March 2001.

26. Association Between Fertility and Education of Girls Percent of Girls Enrolled in Secondary School Total Fertility Rate Source: Population Reference Bureau, Population & Economic Development Linkages 2007 Data Sheet.

27. Association Between Fertility and Female Labor Force Participation Female Labor Force Participation Rate 2004 Total Fertility Rate 2000-2004 Source: United Nations, World Population Prospects: The 2004 Revision, 2005; International Labor Organization, Yearbook of Labor Statistics 2006.

28. Association between fertility and wealth Average Number of Children Born to a Woman During Her Lifetime Source: ORC Macro, Demographic and Health Surveys.

29. Complex associations between female education, economy, and fertility

30. 2. Age Structure of a Population • A large proportion of young people guarantees that population will continue to grow even with declining fertility • Takes two or three generations (70-100 years) before each new birth is offset by a death • Referred to as population momentum

31. Women of Childbearing Age There is a growing population of women in their childbearing years that will contribute to future world population growth even if fertility continues to decline Source: United Nations, World Population Prospects: The 2004 Revision (medium scenario), 2005.

32. Population growth rate Birth rate 3. Mortality • Death is the ultimate determinant of population growth • Falling mortality precedes a decline in fertility Rate Death rate Time

33. Non-communicable Diseases Mortality Rates Infectious diseases Development Development and public healthEpidemiological Transition

34. Systematic Shift in Disease Patterns Type 2 Diabetes Trauma CHD Cancers Mortality Rates Infectious diseases Development

35. Global Burden of Disease – Mortality

36. Global Burden of Disease – DALYs

37. How To Shift Causes of Mortality • Improved sanitation and drinking water supplies • Medical advances (vaccination, antibiotics) • Social advances (improved nutrition, access to health care) • Occupational Health & Safety (injury prevention, chemical safety) • Infrastructure Improvements (roadways, housing, energy) • Consumer Safety (injury prevention, chemical safety) • Economic growth

38. Demographic Transition

39. Public Health Where disease, demographics and development meet

40. Premise • Fertility has a fixed upper limit but not mortality so mortality is the fundamental factor that controls population dynamics • Diseases and injuries control mortality • Investment in public health shifts the causes of death (Epidemiological Transition) and this will influence population structure where women and children benefit the most • During the late phase of the demographic transition when fertility and dependency rates fall countries can harness the demographic dividend when output per capita rises

41. Great Sanitary AwakeningCornerstone of Public Health • Increased immigration to cities during the Industrial Revolution • Analysis of 19th century England revealed urban mortality rates were much higher than rural rates dubbed the “Urban Penalty” • The concept that a government had the moral and ethical responsibility to protect the general welfare of its citizens “Scourge of the Poor”

42. Improved Sanitation and Municipal Water SupplyVirtually eliminated typhoid fever and cholera Typhoid Deaths Redirected sewage discharges away from drinking water intake and water filtration went online in 1906 Philadelphia, USA

43. Public Health Benefits From Municipal Water Supply • In the United States from 1900-1940 • Mortality from diarrheal disease decreases from 140 to 20 per 100,000 • Child mortality rates decrease from 130 to 60 per 1,000 live births • Life expectancy at birth increased by 16 years • Typhoid fever – one of the top 5 causes of death – virtually eliminated • Cost-benefit analysis conducted by Cutler & Miller, 2005 • 1:23 cost-benefit ratio • Every life saved cost $500* resulting in $11,500 gain * 2002 US$

44. Factors contributing to diarrheal disease Access To Safe Water • The source is less than 1 kilometer away from its place of use and reliably produces at least 20 liter per member of a household per day • 1.1 billion people in developing countries have inadequate access to water Access To Sanitation • An excreta disposal system is considered adequate if it is private or shared (but not public) and if it can effectively prevent human, animal, and insect contact with excreta • 2.6 billion people in developing countries lack basic sanitation Hygiene Practices • Increase water quantity allows for more frequent washing practices (hand, food, bathing) which blocks transmission of disease causing pathogens

45. Municipal water supplies are the cheapest source of water for the consumer UNDP, 2006

46. Advanced sanitation is the most expensive for the consumer but has the most health benefits Sanitary Ladder Data from Peru: Having a pit latrine in the home lowers the incidence of diarrhea by 50% while having a flush toilet lowers the risk by 70% UNDP, 2006

47. Method of disposing of human excreta is one of the strongest predictors of child survival UNDP, 2006

48. Access to improved water source WHO Global water supply and sanitation assessment 2000 Access to improved sanitation

49. Current Burden of Waterborne Disease • 2nd largest cause of global child mortality • 1.8 million children die from diarrhea each year • 4931 children a day • 3.4 children a minute • 410 children died during this lecture • Over half of the hospital beds in the developing world are occupied by people suffering from preventable waterborne disease

50. Inequalities in the Use of Health Services Surveys 1992-2001 Average rich/poor ratio 47 countries 50 countries 53 countries 42 countries 53 countries The average of the ratios of the richest quintile to poorest quintile Not weighted for population size and excluding countries with use less than 1% Source: D.R. Gwatkin, S. Rutstein, K. Johnson, E.A. Suliman, and A. Wagstaff, Initial Country-Level Information about Socioeconomic Differences in Health, Nutrition, and Population, Volumes I and II (Washington, DC: The World Bank, November 2003).