1. HSS4303B – Introduction to Epidemiology Jan 14, 2010 – Measures of Morbidity & Mortality Epidemiologists: “Are they smart and good looking, or good looking and smart?" Discuss.

4. So What Has The Lit Review Revealed?

8. So? Do You Have Enough Info To Inform The Patient?

19. Meta-analysis of five hypothetical epidemiologic studies (A–E) of the relationship between reduced dietary fat intake and the risk of developing breast cancer.

25. Heterogeneity statistics for examples of meta-analyses from the literature. Meta-analyses were conducted using either meta or metan in STATA 15 df=degrees of freedom. Heterogeneity test Topic Outcome/ analysis Effect measure No of studies Q df P I 2 (95% uncertainty interval) * Tamoxifen for breast cancer 16 Mortality Peto odds ratio 55 55.9 54 0.40 3 (0 to 28) Streptokinase after myocardial infarction 17 Mortality Odds ratio 33 39.5 32 0.17 19 (0 to 48) Selective serotonin reuptake inhibitors for depression 13 Drop-out Odds ratio 135 179.9 134 0.005 26 (7 to 40) Magnesium for acute myocardial infarction 18 Death Odds ratio 16 40.2 15 0.0004 63 (30 to 78) Magnetic fields and leukaemia 19 All studies Odds ratio 6 15.9 5 0.007 69 (26 to 87) Amantadine 11 Prevention of influenza Odds ratio 8 12.44 7 0.09 44 (0 to 75)

26. Meta-analyses of six case-control studies relating residential exposure to electromagnetic fields to childhood leukaemia. Summary odds ratio calculated by random effects method Eg.

27. Okay, on to today’s topic...

28. Smoking more than one pack of cigarettes a day increases the risk of cardiovascular disease by 70%-80%, and smoking more than two packs per day increases the risk by 200%. Passive smoke increases the risk by 30%. - Basic Res Cardiol 2000 (Suppl I); 95:152-158 normal rate of miscarriage of pregnancy is 2 to 3%, and amniocentesis increases that risk by an additional 1/2 to 1%. - ds-health.com A 1-month delay in treatment for an early-stage primary breast cancer with a 130-day doubling time increases the risk of axillary lymph node involvement by 0.9% - Obstet Gynecol. 1996 Mar;87(3):414-8.

29. A measure of the occurrence of new cases of the disease of interest in a population The probability of obtaining an outcome, given the presence or change in status of an exposure ?

31. In 1022 cancer patients with fever and granulocytopenia, 530 patients developed clinically or microbiologically documented bacterial infections What is the risk of infection in granulocytopenic febrile cancer patients? 530/1022 = 0.518 = 51.8%

32. Remember This?

33. A recent study found that 30% of women who date online have had sex on the first date with gentlemen they've met online. Moreover, the study found that 77% of these women had had unprotected sex in those encounters. -w ww.onlinedatingmagazine.com/news2007/womenonlinedatersrisky.html "When you have unprotected sex with people you are meeting online, you are playing russian roullette [sic] with your health. It's not a matter of 'if' you'll get a sexually transmitted disease, but rather 'when' and 'how many'.” -’STI expert’ responding to the results of the study

35. Canada’s STI Surveillance Report: www.phac-aspc.gc.ca The current prevalence is164 cases per 100,000 population, or about 0.16% of the total population, assuming a conservatively estimated base population of 35 million But is the right prevalence statistic to use?

36. The age-specific chlamydia burden among Canadian men aged 25+ is 9374 cases. Canadian adult male population of about 20 million Risk of Canadian male having Chlamydia = 9374/20000000 = 0.00047 = 0.05% Is that the end of the story?

37. Transmission So far we've been talking about the chances of being exposed to an STI. What about actually contracting one? The transmission rate of Chlamydia is between 30% and 40%. In other words, only 30-40% of sexual encounters with an infected person will result in the disease being transmitted. 30% of 0.05% = 0.015% 40% of 0.05% = 0.020%

38. So, assuming the more conservative estimate (0.02% chance of both exposure and transmission), a Canadian woman would have to sleep with 5000 men to get anything resembling the “guarantee” of an STI that the “expert” suggested. What is wrong with this analysis?

50. http://www.phac-aspc.gc.ca/publicat/haest-tesvs/appendix-eng.php Another Way of Looking at It

51. http://www.phac-aspc.gc.ca/publicat/haest-tesvs/appendix-eng.php

52. http://www.phac-aspc.gc.ca/publicat/haest-tesvs/appendix-eng.php

56. Incidence density = A _______ P x T = A cases ______________ P persons x T time = 28 cases ---------------------- 1000 persons x 2 years = 14 cases ---------- person-years

59. Incidence rates Six patients were observed for 8 years. During that time, 2 were diagnosed with dumbass disease How would you go about computing the incidence rate of dumbass disease over this 8 year period? Cumulative incidence or incidence density?

60. Incidence rates Patient Years at risk A B C D E F

61. Incidence rates Patient Years at risk A B C D E F 2 2 3 7 2 6

62. Incidence rates Incidence rate = A / PT A = 2 PT = 2+2+3+7+2+6 = 22 2 / 22 = 0.09 cases / person-year 9 cases / 100 person-years

63. Acute hepatitis incidence in Canada

65. Identifying new cases: step 1

66. Identifying new cases: step 2

67. Why is incidence important?

68. Expected and observed new cases

69. Prevalence http://www.worldmapper.org/display.php?selected=227 HIV

71. But you can also present it as a percent

72. Or… PR = A ----------------- A + B A = number of cases of the disease B = number of people in the population who do not have the disease, but who are at risk for getting it. Therefore A+B = total number of people in the population

73. Example: Obesity in the USA (from CDC.gov)

76. 23% of this class is left handed In 2008, 28% of Americans were clinically obese Point prevalence Period prevalence Interview Question Type of Measure "Do you currently have asthma?" Point prevalence "Have you had asthma during the last (n) years?" Period prevalence "Have you ever had asthma?" Cumulative incidence

77. Consider an old film camera… A single click of the camera produces an image. The total photons on the film, or dots on the image, constitute the point prevalence . If you leave the shutter open for a few seconds, and point the camera to an unmoving object, then many photons accumulate on the film. This is period prevalence . If you use a movie camera and analyze individual frames, then the number of new events in each frame constitute the incidence rate for that frame.

78. Incidence and prevalence

80. Point prevalence for positive x-rays Table 3-7. Hypothetical Example of Chest X-Ray Screening: II. Point Prevalence Screened Population No. with Positive X-Ray Point Prevalence per 1,000 Population 1,000 Hitown 100 100 1,000 Lotown 60 60 Table 3-8. Hypothetical Example of Chest X-Ray Screening: III. Prevalence, Incidence, and Duration Screened Population Point Prevalence per 1,000 Incidence (Occurrences/yr) Duration (yrs) Hitown 100 4 25 Lotown 60 20 3 Prevalence = Incidence × Duration

81. Breast cancer incidence

87. The crude death rate , the total number of deaths per year per 1000 people. The crude death rate for the whole world is currently about 8.24 per 1000 per year (according to the current CIA World Factbook.) The perinatal mortality rate , the sum of neonatal deaths and fetal deaths (stillbirths) per 1000 births. (WHO -> 22 weeks pregnancy until 7 days of life) The maternal mortality rate , the number of maternal deaths due to childbearing per 100,000 live births. The infant mortality rate , the number of deaths of children less than 1 year old per 1000 live births. The child mortality rate , the number of deaths of children less than 5 years old per 1000 live births. The standardised mortality rate (SMR)- This represents a proportional comparison to the numbers of deaths that would have been expected if the population had been of a standard composition in terms of age, gender, etc. The age-specific mortality rate (ASMR) - This refers to the total number of deaths per year per 1000 people of a given age (e.g. age 62 last birthday).

88. Infant, neonatal, and postneonatal mortality rates: United States, 1940-2005 (Wikipedia)

92. Google public data.

94. Selected leading causes of death, by sex in Canada 1997 Number % Total Males Females Rate 1 All causes 215,669 100.0 658.7 844.0 521.6 Cancers 58,703 27.2 181.5 229.7 148.5 Diseases of the heart 57,417 26.6 173.0 230.8 129.7 Cerebrovascular diseases 16,051 7.4 47.8 52.8 43.9 Chronic obstructive pulmonary diseases and allied conditions 9,618 4.5 29.0 44.5 20.1 Unintentional injuries 8,626 4.0 27.6 37.8 17.9 Pneumonia and influenza 8,032 3.7 23.7 31.5 19.2 Diabetes mellitus 5,699 2.6 17.4 20.6 14.8 Hereditary and degenerative diseases of the central nervous system 5,049 2.3 15.0 16.7 13.9 Diseases of arteries, arterioles and capillaries 4,767 2.2 14.3 19.5 10.6 Psychoses 4,645 2.2 13.6 13.3 13.4 Suicide 3,681 1.7 12.0 19.5 4.9

98. Example: crude data from the Canadian Injuries Surveillance System: Leading causes of death due to injury, 2004 -passive system based on automatic processing of death certificates and hospital charts

99. Example: Canadian Notifiable Disease Surveillance Report, June 2007 (Ontario is blank because no data was available from Ontario in June/2007) Active system requiring doctors to call the government when certain illness arise