DrugEpi 4-1 Introduction to Interpreting Associations Module 4 Overview Context Content Area: Interpretation of Epidemiological Evidence Essential Question (Generic): Is the association causal? Essential Question (Drug Abuse Specific): Is an association with drug abuse causal? Enduring Epidemiological Understanding: Causation is only one explanation for finding an association between an exposure and a disease. Because observational studies are complicated by factors not controlled by the observer, other explanations must also be considered. Synopsis: In Module 4, students explore the rationale and methods of interpreting epidemiological studies. Students develop skills to assess possible explanations for an association found in a study, with consideration of explanations of causality, chance, confounding, reversed time order, and bias. Module 4 concludes with consideration of methods for weighing the overall evidence for an association. Lessons: Lesson 4-1: Introduction to Interpreting Associations Lesson 4-2: Causality Lesson 4-3: Chance Lesson 4-4: Bias Lesson 4-5: Confounding Lesson 4-6: Reverse Time Order Lesson 4-7: Weighing the Evidence

DrugEpi 4-1 Introduction to Interpreting Associations Module 4 - Interpretation of Epidemiological Evidence Lesson 4-1 Introduction to Interpreting Associations Content Review of definition of association Distinction between association and causation Five possible explanations for an association Big Ideas Association does not necessarily mean causation When an association is found in a study, several possible explanations must be considered, including causality, chance, bias, confounding, and reverse time order This project is supported by a Science Education Drug Abuse Partnership Award, Grant Number 1R24DA , from the National Institute on Drug Abuse, National Institutes of Health.

DrugEpi 4-1 Introduction to Interpreting Associations Where are we? Essential QuestionsEnduring Understandings 1.How is this disease distributed? Health-related conditions and behaviors are not distributed uniformly in a population. They have unique distributions that can be described by how they are distributed in terms of person, place, and time. 2.What hypotheses might explain the distribution of disease? Clues for formulating hypotheses can be found by observing the way a health-related condition or behavior is distributed in a population. 3.Is there an association between the hypothesized cause and the disease? Causal hypotheses can be tested by observing exposures and diseases of people as they go about their daily lives. Information from these observational studies can be used to make and compare rates and identify associations. 4.Is the association causal? Causation is only one explanation for an association between an exposure and a disease. Because observational studies are complicated by factors not controlled by the observer, other explanations also must be considered. 5.What should be done when preventable causes of disease are found? Policy decisions are based on more than the scientific evidence. Because of competing values - social, economic, ethical, environmental, cultural, and political factors may also be considered.

DrugEpi 4-1 Introduction to Interpreting Associations Concept Map So Far... The Science of Public Health: Epidemiology Hypothesis Total RiskRelative Risk a b c d or % % Exposure Outcom e ? Turned Up Together Healthy People - E E DZ

DrugEpi 4-1 Introduction to Interpreting Associations Concept Map.. Where We Are Going... Hypothesis Total RiskRelative Risk a b c d or % % Exposure Outcom e ? Turned Up Together Healthy People - E E DZ Person, Place, Time Surveillance Testing Hypotheses Interpretation?

DrugEpi 4-1 Introduction to Interpreting Associations What do we mean when we say that there is an association between two things? Associated TiedRelated Linked Things that are associated are linked in some way that makes them turn up together. Review - Definition of an Association Optional - Use if needed for a concept connection

DrugEpi 4-1 Introduction to Interpreting Associations Outcome ab cd Exposure No Exposure No Outcome Exposure Review - Showing that Things Turn Up Together Optional - Use if needed for a concept connection

DrugEpi 4-1 Introduction to Interpreting Associations To give the meaning of, explain, or make clear. Interpret Study Interpretation

DrugEpi 4-1 Introduction to Interpreting Associations Suicide Higher in Areas with Guns Smoking Linked to Youth Eating Disorders Snacks Key to Kids’ TV- Linked Obesity: China Study Family Meals Are Good for Mental Health Lack of High School Diploma Tied to US Death Rate Study Links Spanking to Aggression Breakfast Each Day May Keep Colds Away Study Concludes: Movies Influence Youth Smoking Study Links Iron Deficiency to Math Scores Kids Who Watch R-Rated Movies More Likely to Drink, Smoke Pollution Linked with Birth Defects in US Study Depressed Teens More Likely to Smoke Review - Things That Turn Up Together

DrugEpi 4-1 Introduction to Interpreting Associations IS ASSOCIATED WITH ININ Is the Association Causal?

DrugEpi 4-1 Introduction to Interpreting Associations Suicide Higher in Areas with Guns Family Meals Are Good for Mental Health Lack of High School Diploma Tied to US Death Rate Study Links Spanking to Aggression Study Concludes: Movies Influence Youth Smoking Study Links Iron Deficiency to Math Scores Kids Who Watch R-Rated Movies More Likely to Drink, Smoke Pollution Linked with Birth Defects in US Study Possible Reasons Why Things Turn Up Together 1.Cause 2.Chance 3.Bias 4. Confounding 5.Reverse Time Order Snacks Key to Kids’ TV- Linked Obesity: China Study Depressed Teens More Likely to Smoke

DrugEpi 4-1 Introduction to Interpreting Associations Exercise in Interpreting an Association Association Found Between Coffee and Pancreatic Cancer

DrugEpi 4-1 Introduction to Interpreting Associations 1.Cause Possible Explanations for Finding an Association

DrugEpi 4-1 Introduction to Interpreting Associations Anything that produces an effect Cause Explanation 1 - Causal

DrugEpi 4-1 Introduction to Interpreting Associations An exposure that increases the likelihood of a specific outcome. Risk Factor Explanation 1 - Causal

DrugEpi 4-1 Introduction to Interpreting Associations Some high school students’ answers that indicate they think that “association always means causation” “Association means that the two things are related, or that one leads to another or one is the cause / effect of the other.” “When you say that two things are associated with each other you mean that there is a direct relation between the two things - that one thing can cause another thing to occur.” “To be ‘associated with’ as in the context of coffee and pancreatic cancer means that coffee is a cause or at least part of the etiology which results in pancreatic cancer.“ “An addition or lack of one thing will cause an appreciable change in the other.” “When it is said, something associated with another, it means that they share a common bond, usually one of cause and effect.” Explanation 1 - Causal

DrugEpi 4-1 Introduction to Interpreting Associations 1.Cause 2.Chance Possible Explanations for Finding an Association

DrugEpi 4-1 Introduction to Interpreting Associations Chance Explanation 2 - Chance To occur accidentally To occur without design A coincidence

DrugEpi 4-1 Introduction to Interpreting Associations 1.Cause 2.Chance 3.Bias Possible Explanations for Finding an Association

DrugEpi 4-1 Introduction to Interpreting Associations Bias Any systematic error in the design, conduct, or analysis of a study that results in a mistaken estimate of an exposure’s effect on the risk of the outcome. Explanation 5 - Study Bias Leon Gordis, Epidemiology, 3rd Edition, Elsevier Saunders, 2004.

DrugEpi 4-1 Introduction to Interpreting Associations 1.Cause 2.Chance 3.Bias 4. Confounding 5. Possible Explanations for Finding an Association

DrugEpi 4-1 Introduction to Interpreting Associations Confounding Explanation 3 - Confounding A situation in which an association between a given exposure and an outcome is observed as a result of the influence of a third unobserved factor, called a confounder.

DrugEpi 4-1 Introduction to Interpreting Associations Confounding Explanation 3 - Confounding A situation in which an association between a given exposure (match carrying) and an outcome (lung cancer) is observed as a result of the influence of a third unobserved factor, called a confounder (smoking) Obviously we should have measured smoking

DrugEpi 4-1 Introduction to Interpreting Associations Cause Association Cause X Observed Not Observed Confounder Match- Carrying Lung Cancer Diagram of Confounding Smoking

DrugEpi 4-1 Introduction to Interpreting Associations 1.Cause 2.Chance 3.Bias 4. Confounding 5.Reverse Time Order Possible Explanations for Finding an Association

DrugEpi 4-1 Introduction to Interpreting Associations EggChicken Outcome Explanation 4 - Reverse Time Order Hypothesized Exposure ?

DrugEpi 4-1 Introduction to Interpreting Associations Hypothesized Exposure Outcome Explanation 4 - Reverse Time Order Playing Violent Video Games Violent Behavior

DrugEpi 4-1 Introduction to Interpreting Associations 1.Cause 2.Chance 3.Bias 4. Confounding 5.Reverse Time Order The Science of Public Health: Epidemiology Possible Explanations for Finding an Association To reiterate...

DrugEpi 4-1 Introduction to Interpreting Associations... the study of the distribution and determinants of health-related states or events in specified populations and the application of this study to the control of health problems. (Gordis, 2004) Review - Definition and Purpose of Epidemiology How do the five possible explanations relate to the idea that epidemiology studies are done for purposes of eventually controlling health problems?

DrugEpi 4-1 Introduction to Interpreting Associations Outcome If an association was causal, …. Exposure X X … and you avoided or eliminated the hypothesized cause, what would happen to the outcome? causal, …. ? Possible Explanations for Finding an Association

DrugEpi 4-1 Introduction to Interpreting Associations Outcome If an association was found due to chance, …. Exposure found due to chance, …. Possible Explanations for Finding an Association X … and you avoided or eliminated the hypothesized cause, what would happen to the outcome? ?

DrugEpi 4-1 Introduction to Interpreting Associations Outcome If an association was found due to bias, …. Exposure ? found due to bias, …. Possible Explanations for Finding an Association X … and you avoided or eliminated the hypothesized cause, what would happen to the outcome?

DrugEpi 4-1 Introduction to Interpreting Associations Outcome If the association was found due to confounding, …. Exposure Unobserved Exposure Possible Explanations for Finding an Association X … and you avoided or eliminated the hypothesized cause, what would happen to the outcome? ? found due to confounding, ….

DrugEpi 4-1 Introduction to Interpreting Associations ExposureOutcome If an association was found due to reversed time-order, …. found due to reverse time order, …. Possible Explanations for Finding an Association X … and you avoided or eliminated the hypothesized cause, what would happen to the outcome? ?

DrugEpi 4-1 Introduction to Interpreting Associations So with one explanation - causality - removing the exposure away would lead to prevention But for the other four explanations - chance, confounding, reverse time order and bias - removing the exposure won’t change anything So we need to interpret studies correctly to avoid wasting time and resources on preventing exposures that will not lead to prevention of disease Big Ideas

DrugEpi 4-1 Introduction to Interpreting Associations Exercise in Interpreting an Association Association Found Between Coffee and Pancreatic Cancer Optional

DrugEpi 4-1 Introduction to Interpreting Associations Association is not necessarily causation. Always Remember

DrugEpi 4-1 Introduction to Interpreting Associations Association is not necessarily causation. Don’t Forget

DrugEpi 4-1 Introduction to Interpreting Associations Big Ideas in this Lesson (4-1) Association does not necessarily mean causation When an association is found in a study, several possible explanations must be considered, including causality, chance, bias, confounding, and reverse time order This project is supported by a Science Education Drug Abuse Partnership Award, Grant Number 1R24DA , from the National Institute on Drug Abuse, National Institutes of Health. Re-Cap

DrugEpi 4-1 Introduction to Interpreting Associations Next Lesson Causality SURGEON GENERAL’S WARNING: Smoking Causes Lung Cancer, Heart Disease, Emphysema, and May Complicate Pregnancy