Lec 1 & Tut 1 notes

Question 1

• Define epi
• focus

Answer 1

Epi: the study of distribution, freq, and determinants of health and disease w/in pop, and the application of this K to improve pop health

• Focus on population

Question 2

• descriptive
  
  • focus
  • method
  • sign of high risk population
  • 3 key characteristics of descriptive epi
  • disparities can help us see 2 things:
• analytic epi
  
  • focus
  • methods
  • IOW

Answer 2

2 main areas of epi

• # 1: Descriptive epi
  • Focus: distribution of heath-related states or events in specified pop
  • method: Use available data to examine how rates (eg mortality) vary according to demographic v
  • If the distribution of rates is not uniform according to person, time and place; this indicates a high-risk population
    
    • Eg: COVID outbreak in community in a specific time frame, people of certain ages and SES are more affected
      
      • Identify high risk populations
    • Basic triad of descriptive epi: the 3 essential characteristics of disease we look in descriptive epi: Time place person
  • Disparities can
    
    • Generate causal H
    • Identify gaps in the health system
      
      • If there are gaps -> need more services
• # 2: analytic epi
  • Focus on DETERMINANTS of health-related states or events in specified pop
  • Methods: assessment of specific hypotheses on suspected RF w/ health outcomes
    
    • IOW: understand why certain pop are higher risk
  • Observational vs experimental studies

Question 3

5 objectives of epi

Answer 3

Objectives of epi

• # 1: study the natural course of disease (from onset to resolution)
• # 2: measure the extend of disease in a pop
  • IOW: how common is the disease
• # 3: identify patterns and trends in disease occurrence
  • IOW: is the disease more common or less; more common in certain gps
• # 4: determine the causes of disease
• # 5: eval the effectiveness of measures that prevent and treat disease
  • Eg on application
• Repeat process
• Why do we do this (reiterative process)? Some interventions are working; when they do not work, we alter it so that it works again

Question 4

• descriptive/applied epi
• analytic/academic epi
• applied epi; academic
  
  • practice setting
  • investigative team
  • goals
  • timeline
  • data quality
  • RF investigate
  • Scientific values
  • outputs
  • competence

Answer 4

What do epidemiologists do?

• They work in various facilities
• Descriptive or applied epi: the timeline is frequent and urgent; focus on public health
• Academic or analytic epi: done in academic institutions, look into more details
• X
• Arguable aspects:
  
  • We don’t always do biomed, we may look at social determinants of health
  • We work w/ diff disciplines and in teams
• Table 1: comparison of characteristics applied epi and academic epi
  
  • Applied epi
    
    • Practice setting: more governmental
    • Investigative team: Maybe interdisciplinary
    • Goals: Service (eg public health surveillance, responding to outbreaks, improving health)
    • Timeline: urgent
    • Data quality: variable, collected in real-life
    • RF investigated: sociologic, determinants of health
    • Scientific values: urgency, practical, responsive, health impact
    • Outputs: recommendations, product removal, PH action
    • Competences: communication skills, community engagement, analytic
    • Taught: on the job
  • Academic epi
    
    • Practice setting: school of PH, academic
    • Investigative team: PhD, Maybe interdisciplinary
    • Goals: discovery (etiology, RF, causality, disease modelling)
    • Timeline: not urgent
    • Data quality: high, data collected in controlled circumstances
    • RF investigated: varies
    • Scientific values: analytic rigor; consistency w/ prior studies
    • Outputs: contribute to literature
    • Competencies: strong analytic skills
    • Taught: academic institution
      *

Question 5

• 6 PH areas of focus
• PH health goal
• define health
• intervention vs prevention

Answer 5

Many different areas of focus

• Methods
• Env health
• PH policy
• Chronic disease
• MH
• Infectious diseases

Public health

• Goal: promote the health of the population through organized community efforts
  
  • What do we mean by health?
    
    • Physical, mental, social wellbeing
    • Not just absence of disease
    • Essential resources of living
  • intervention vs prevention
    
    • PH: focuses on interventions
      
      • (eg Laws for seatbelts, helmets, bike lanes, smoking cessation)
    • Clinical: focus on prevention

Question 6

• basic science; clinical; PH science
  
  • study
  • goal
  • example
• 9 aspects of PH
• Define upstream

Answer 6

Basic, clinical, and PH sciences

• They work together for the same goals and different parts
• Basic Science
  
  • Study: cells, tissues, animals in labs
  • Goals: understand disease mech, and effects of toxic substances
  • Eg: Toxicology, immunology
• Clinical
  
  • Study: sick patients who come to healthcare facility
  • Goals: improve diagnosis and treat disease
  • Eg: internal med, pediatrics
• PH
  
  • Study: population, communities
  • Goals: prevention of disease, promote health
  • Eg: epi, env science
• These branches of science are not that distinct
  
  • Clinical epi
  • Molecular and genetic epi
  • Econ, sociology, psych

Public health: more than just the indiv

• Aspects include
  
  • Indiv and pop health
  • Patho-physiologic pathways
  • Genetic/constitutional factors
  • Indiv RF
  • Social relationships (married men visit family MD more than single men)
  • Living conditions
  • Neighborhoods and communities (safer env -> more activity)
  • Institutions
  • Social and econ policies
• These aspects change, influence eo, and in turn our health
• Upstream: other factors that impact health beyond indiv ones

Question 7

• Epi lv of study
• Lv of intervention
• Paradigm

Answer 7

Present day epi

• Motivation: PH and scientific discovery
• Lv of study: molecular to human pop
• Lv of intervention: indiv to pop
• Paradigm: multidisciplinary

Question 8

• define population
• define sample
• census
• define healthcare encounter data
• registries
• x
• Define count
• proportion calculation
• Ratio
• How to check the ratio form?
• Marble analogy for incidence and prevalence
• x
• Relationship b/w prevalence and incidence formula

Answer 8

Topics throughout this course

Population

• A gp of ppl w/ a common characteristic
  
  • Residence
  • Gender
  • Age
  • Life event (birth)
  • Other demographics
  • Disease cohorts
• Sample = subset of pop

Data

• Census: (all ppl living in Canada, every 5 years; on age, sex, occupation)
• Vital stats: all births, deaths, marriages, etc reported to the gov (eg Bills of Mortality)
• Health care encounter data (eg hospitalizations)
  
  • Health administrative data collected during routine care
  • Esp good data source in CAN due to universal care
  • ON ICES: global leader in using the data (and link to other pop data)
    
    • NOTE: in US only collect data for 1 type of insurer
  • Registries: incl ppl w/ specific conditions (eg cancer)
  • Reportable diseases: those of PH importance needs to be reported by MD (eg Polio, Anthrax)

Measure of freq

• Count: absolute #
• Proportion:
  
  • N: subset of denom
  • Ppl with event/ Ppl with event + ppl without
    
    • IOW: A/(A+B)
  • Expressed in fraction, decimal, or %
• Ratio: value obtained by dividing one quantity over another
  
  • Scenario: 100 ppl in class, 50 brown hair
  • IOW: 50% brown hair
  • Proportion: 50/100 or ½
  • Ratio form: for every 1 person w/ brown hair there is 1 person w/o
    
    • (1:1)
    • NOTE: data is not related
    • The 2 #s should add up to the numerator proportion (i.e. 1+1 = 2)
• X
• Analogy
  
  • Marble = sick person
  • Marble dropped: incidence
  • Marbles in bucket: prevalence

Question

• 1980s: incidence of HIV declined and prevalence increased
  
  • Possible explanations
    
    • Tools to identify more cases
    • Ppl live longer
    • Incidence down, duration of disease increases
• Why?
• Prevalence = Incidence x Duration of disease

Question 9

• 3 types of incidence measure:
• Define cumulative incidence
• 2 other names
• Calculation
• x
• 2 other names for incidence rate
• calculation
• What does it address?
• x
• define prevalence
• Calculation
• rate or proportion?

Answer 9

Types of incidence measure

• # 1: Cumulative incidence (aka risk, incidence proportion)
  • Risk indiv will experience an event or dev a disease during a period of time
  • Cumulative incidence = new cases in given time period/# of ppl at risk x 100
  • 24 infected/25 * 100
• # 2: Person-time (or year) incidence or incidence density or incidence rate
  • Occurrence of new case of disease that dev in a candidate pop over a specified time period
  • P-t incidence rate = (# of new cases/ person-time of observation in candidate population at risk) x 1000
  • Addresses: Handles loss to follow up, diff times
• # 3: Prevalence: # of ppl in a population during a specific time frame that have disease of interest
  • Prevalence = # of cases / # of persons in the population
    
    • Eg 13/15 Iphone users
  • NOTE prevalence is NOT a rate, it is proportion