WEEK 7: Study Designs

Epidemiological Study Designs: Observational Studies

– researcher does not intervene in any way;

• Measurement of occurrence of disease or health outcome

• Comparing patterns of exposure and disease outcomes

• Identifying risk factors associated with health/disease

• Descriptive and analytical

Experimental studies

investigator tries to change something and measure the effect on disease outcome – clinical trials, preventive trials

Descriptive Studies

Research that describes the occurrence of disease and/or exposure.

Remember: PERSON PLACE TIME

Ask: WHO? WHAT? WHEN? WHERE?

Case reports / case series

• detailed descriptions usually by a doctor or group of doctors identifying diseases that are unusual/interesting;

may be related to unusual exposure

Analytic Studies

Primary purpose is to evaluate the ASSOCIATION between an

EXPOSURE or CHARACTERISTIC and the development of a

particular disease

WHY?

HOW STRONG?

What’s an Exposure?

can include:

◦ Infectious agents

◦ Behaviours

◦ Intrinsic characteristics of individuals

◦ Social or environmental factors

Ecological Studies

Compare the prevalence of exposures and disease occurrence in populations

Cross-Sectional Studies

• snapshot of the population at single point in time

• Study group often chosen to be representative of a population

Different groups

Case-Control Study

• Choose individuals with disease or outcome of interest (cases) and a

comparison group without the disease (controls)

• Multiple ways for selecting the control group

• Retrospective

• Comparison is the odds of exposure

Prospective Cohort Studies (Longitudinal)

Follow-up studies: follow people OVER TIME to see what happens

• Compare rates of occurrence of disease in people with or without a

particular exposure

• susceptible to loss of follow up

Randomized Controlled Trial

• evaluates safety, efficiency, or efficacy of a medical intervention (new drug) by assigning people to different groups

What Makes People Healthy?

Personal Determinants of Health

Personal determinants – individual level

• Lay health beliefs

• Self-health management

◦ Self-care capacity

◦ Coping skills

• Biology and genetic endowment

• Health protective behaviour

◦ Personal health practices

◦ Healthy lifestyles

What makes people healthy?

Structural Determinants of Health

• Social environment

◦ Socioeconomic status AKA Socio-economic position

◦ Social status

◦ Income and income distribution

◦ Education

◦ Employment & working conditions

◦ Gender, ethnicity/race, age, culture

◦ Social support networks

• Physical environment

• Health-care & social services

◦ Disease prevention

◦ Health promotion

◦ Healthy child development

Origins of Upstream/Determinants of Health

Perspectives

• Lalonde report

• Ottawa charter for health promotion (education, shelter, healthcare etc.)

• Population health concept

• The WHO commission on social determinants of health

What happened in 1848

• worldwide cholera epidemic

Early Evidence: Friedrich Engels’ Study (1844)

• Method: Examined observed differences in mortality rates in suburbs of Manchester

• Findings: observed death rates correlated with quality of housing and quality of streets

Early Evidence: Rudolf Virchow’s Study

• Preserving health and preventing disease requires “full and unlimited democracy“ and radical measures rather than mere palliatives

Public Health Agencies of Canada: 12 Key determinants

• Income and Social Status

• Social Support Networks

• Education and Literacy

• Employment/Working Conditions

• Social Environments

• Physical Environments

• Personal Health Practices &

Coping Skills

• Healthy Child Development

• Biology and Genetic Endowment

• Health Services

• Gender

• Culture

The Social Gradient In Health

• graded association between the indicator of socioeconomic status and population health

Micheal Marmot: where you stand in the social hierarchy is intimately related to your chances of getting ill and your length of life

The Link Between Social Class & Health: Socio-Economic Position (SEP)

Social and economic factors that influence what position individuals and groups hold in the social structure of a society

Measurement:

• Individual Level Measures:

◦ Occupation

◦ Income

◦ Income in relation to poverty level

◦ Education

◦ Wealth

• Area Based Measures:

◦ Geographic area

How Does SEP Impact Health?

• Political, cultural and institutional factors influence HOW

• socio-economic conditions influence health outcomes

• Location in society

• exposures and resources used for health

Example:

Mortality on the Titanic

Income & Children’s Health

National Longitudinal Study on

Children and Youth)

Income associated with:

• Low birth weight

• Injury related mortality (fire and homicide deaths)

• Developmental problems (hyperactivity, psychosocial problems,

delinquent behavior, delayed vocabulary)

Explanations of Social Gradient

1. Materialist Explanations

2. Cultural Behavioural Explanations

3. Psychosocial Explanations

Materialist Explanations: Differential Exposure hypothesis

greater exposure to psychosocial stressors from financial problems, neighbourhood issues and social isolation

Materialist explanations: Exposure

People exposed to positive and negative exposures over the life

course and outcomes in adulthood are indicators of advantages and

disadvantages…

• …and differences in exposure to stress influence biological factors that

influence health outcomes

Materialist vs Neo-materialist Explanations

• First explanation emphasizes the material conditions under which people live

• Second explanation:

  ◦ Health is affected not only by differential access to social and economic resources

  ◦ Also by the level of funding invested in social infrastructure

Cultural Behavioural Explanations

How we learn how we behave in society

Differential vulnerability hypothesis

We all have stressors; position in social gradient can help mitigate or make these worse

Psychosocial explanations

People’s interpretation of their standing in the social hierarchy matters

• Sense of relative deprivation can generate feelings of low self-esteem,

shame, envy

• Strive and fail à negative health consequences

Social Comparison

• perception and understanding of where people are in social structure

• perception of hierarchy leads to stress comparisons lead to shame, envy, other mental health outcomes and/or other negative behaviours

Explanations of social gradient

• Assessment of social status

• Reasons for own disadvantages social status

• Comparative group

• Social comparisons and health