2015 - epidemiology presentation slides(1)

College of Public Health

Epidemiology

CMD-80325: Public Health Jurisprudence

Lynette Phillips, PhD, MSPH


What is “Epidemiology”?

2

Jim Borgman, The Cincinnati Enquirer, 1997.


BATTLING BAD SCIENCE: DR. BEN GOLDACRE

http://www.ted.com/talks/ben_goldacre_battling_bad_science?language=en





Questions:

• Did any of this surprise you? • What was the main message? • What does he mean by “sunlight”?

• Epidemiology: The sunlight in health

knowledge


Epidemiology Overview

Epidemiology

Descriptive Epidemiology

Descriptive Studies Surveillance

Analytic Epidemiology

Experimental Studies

Clinical Trials

Observational Studies

Cohort Studies

Case-Control Studies


Descriptive Epidemiology

• Studies the frequency and pattern of health problems in specified populations by person, place, and time

• Describes populations and health problems • Involves conducting surveillance • Answers the questions “Who?”, “What?”,

“Where?”, and “When?”


Analytic Epidemiology

• Uses comparison groups to quantify the associations between determinants and health problems

• Tests hypotheses about causal relationships

• Involves studies concerned with identifying health-related causes and effects

• Answers the questions “How?” and “Why?”


Epidemiology & Public Health

3 Core Functions – 10 Essential Services

8


A trip to 1850s London

• Cholera outbreaks: – 1832 – 1848-49 – 1853


Dr. John Snow

• Everyone thought cholera was spread by “bad air”

• Snow’s hypothesis: poison found in feces and vomit of cholera patients, transmitted by contaminated drinking water

• How to test this theory?


Observations

• Who was getting the disease? • What characteristics were tracking with

disease? • Where were the cases located? • When did they occur? • Why might they have been occuring?


The process

• Found the “index case”: a merchant seaman who arrived from Hamburg by ship on Sept. 22, 1848, rented a room in London, developed symptoms and died

• 2nd man to rent the same room also contracted cholera and died 8 days later (Snow suspected room hadn’t been cleaned thoroughly between renters)

• Began seeing sick patients, all who complained of digestive problems first


The process (cont.)

• Few cases of cholera between 1849 and 1853

• During this time, Snow kept working on his theory

• Published “On the Mode of Communication of Cholera” pamphlet in August 1849

• Gave talks; was well known as a pioneer in anesthesiology


New epidemic: Summer 1853

• New huge increase in cholera cases in area of London where Snow was practicing (Soho district)

• Found out two private companies were supplying water to the district: – Southward and Vauxhall drew water from an

area along the Thames known to be polluted by sewage

– Lambeth recently had moved its intake to a location above the sewer outlets


Comparing death rates by water company


Collecting data

• Took water samples from area pumps; insufficient evidence of contamination

• Gathered statistical evidence to compile the (now famous) map: where victims lived, where they got their water – 61/73 (83.5%) victims had drunk the water

from the Broad Street pump – 14/73 (19.2%) would have been expected as

part of a general outbreak in London


Is this statistically significantly different?

• Two-sample z-test:

𝑧 =𝑝�1 − 𝑝�2

𝑝�1(1 − 𝑝�1)𝑛1

+ 𝑝�2(1 − 𝑝�2)𝑛2

=0.835 − 0.192

(0.835)(0.165)73 + (0.192)(0.808)

73

=0.6430.063

= 10.2,𝑝 − 𝑣𝑣𝑣𝑣𝑣 < 0.0001


What about cases that couldn’t be explained by the broad street pump hypothesis? • A woman and her niece lived elsewhere

but died from cholera during the outbreak • Few workers from Poland Street

Workhouse and none from brewery in neighborhood contracted cholera


Conclusion?

Remove the handle of the Broad Street Pump


Changing Emphasis

Figure 1-5: US Crude Death Rates for Infectious Diseases


Changing Emphasis

National Center for Health Statistics, National Vital Statistics Report. Vol 54, no 19, June 2006


A trip to 1940s Massachusetts


Framingham Heart Study

• National Heart Institute (now the National Heart, Lung and Blood Institute, or NHLBI) wanted to know more about general causes of heart disease and stroke

• Recruitment of 5209 men and women between 30 and 62 from Framingham, MA

• Extensive physical exams and lifestyle interviews; follow-up every two years


Framingham Heart Study

• 1971: Offspring study recruited (5124 of the original participants’ adult children and their spouses)

• 1994: Omni cohort (includes more diversity, from current Framingham population)

• 2002: Grandchildren of original cohort


Research Milestones 1960 Cigarette smoking found to increase the risk of heart disease 1961 Cholesterol level, blood pressure, and electrocardiogram abnormalities found to increase the risk of heart disease 1967 Physical activity found to reduce the risk of heart disease and obesity to increase the risk of heart disease 1970 High blood pressure found to increase the risk of stroke 1970 Atrial fibrillation increases stroke risk 5-fold 1976 Menopause found to increase the risk of heart disease 1978 Psychosocial factors found to affect heart disease 1988 High levels of HDL cholesterol found to reduce risk of death 1994 Enlarged left ventricle (one of two lower chambers of the heart) shown to increase the risk of stroke 1996 Progression from hypertension to heart failure described 1998 Framingham Heart Study researchers identify that atrial fibrillation is associated with an increased risk of all-cause mortality. 1998 Development of simple coronary disease prediction algorithm involving risk factor categories to allow physicians to predict multivariate coronary heart

disease risk in patients without overt CHD 1999 Lifetime risk at age 40 years of developing coronary heart disease is one in two for men and one in three for women 2002 Obesity is a risk factor for heart failure. 2004 Serum aldosterone levels predict future risk of hypertension in non-hypertensive individuals. 2005 Lifetime risk of becoming overweight exceeds 70 percent, that for obesity approximates 1 in 2. 2008 Based on analysis of a social network of 12,067 people participating in the Framingham Heart Study (FHS), researchers discover that social networks

exert key influences on decision to quit smoking. 2008 Discovery by Framingham Heart Study and publication of four risk factors that raise probability of developing precursor of heart failure; new 30-year risk

estimates developed for serious cardiac events. 2009 A new genetic variant associated with increased susceptibility for atrial fibrillation, a prominent risk factor for stroke and heart failure, is reported in two

studies based on data from the Framingham Heart Study. 2009 Framingham Heart Study researchers find parental dementia may lead to poor memory in middle-aged adults. 2009 Framingham Heart Study researchers find high leptin levels may protect against Alzheimer's disease and dementia 2010 Sleep apnea tied to increased risk of stroke 2010 Framingham Heart Study researchers identify additional genes that may play a role in Alzheimer's disease 2010 Framingham Heart Study finds genes link puberty timing and body fat in women 2010 Having first-degree relative with atrial fibrillation associated with increased risk for this disorder 2010 First definitive evidence that occurrence of stroke by age 65 years in a parent increased risk of stroke in offspring by 3-fold


WHAT CAN BE DONE WITH THESE DATA?


Using Epidemiologic Data from Framingham Heart Study

• Who: Risk of heart disease differs between men and women; specifically, women experience heart disease later in life than men but with equal overall lifetime risk

• What: These results helped clinicians and researchers to take CHD seriously in women as well as in men.



• Where: Risk of heart disease is highest in the southeastern areas of the United States



• When: Heart disease mortality has decreased, but prevalence has increased (due mostly to lifestyle changes)

Source: http://nccd.cdc.gov/DHDSP_DTM/DetailedData.aspx?State=United+States&Category=7&Indicator=42&stratification=Total

Source: http://www.who.int/cardiovascular_diseases/en/cvd_atlas_14_deathHD.pdf?ua=1


For your class projects:

• Describe the problem: – Who does it affect – What are the risk factors – Where are the highest rates (incidence,

prevalence, and mortality) – When is the disease most problematic (Early

age? Under certain conditions or in specific socioeconomic categories? Etc.)

– Why is this a particular problem that needs to be addressed? Is there an economic or public health burden associated with it?


For your class projects:

• Sources of epidemiologic data: – The World Health Organization (www.who.int) – The Centers for Disease Control and Prevention

(www.cdc.gov) – The National Institutes of Health (www.nih.gov)

• NHLBI for heart, lung, and blood diseases • NCI for cancer

– National or international non-profit organizations: • American Heart Association (www.heart.org) • American Lung Association (www.lung.org) • American Diabetes Association (www.diabetes.org) • American Cancer Society (www.cancer.org)

http://www.who.it/

http://www.cdc.gov/

http://www.nih.gov/

http://www.heart.org/

http://www.lung.org/

http://www.diabetes.org/

http://www.cancer.org/

2015 - epidemiology presentation slides(1)

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