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Definition of Demography - Park's Textbook of PSM

"Demography, as understood today, is the scientific study of human population. It focuses its attention on three readily observable human phenomena: (a) changes in population size (growth or decline); (b) the composition of the population; and (c) the distribution of population in space."

• Park's Textbook of Preventive and Social Medicine, Chapter 10 (Demography), p. 566

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The Five Demographic Processes

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Relevance to Community Medicine

• The numbers of people
• The space they occupy
• The skills they have acquired in providing for their needs

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Main Sources of Demographic Statistics in India

1. Population censuses
2. National Sample Surveys
3. Registration of vital events
4. Ad hoc demographic studies

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The Demographic Cycle (5 Stages)

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1. The database query confirmed the book: The library database contains "Park's Textbook of Preventive and Social Medicine" with ISBN 9789382219163.
2. I read the actual file: The text was pulled directly from the file /textbooks/9789382219163/9789382219163_block7.md at line 6434, not generated from my own knowledge.
3. The exact text I quoted:

   "Demography, as understood today, is the scientific study of human population..."

   ...appears word-for-word in that file at lines 6434-6442.
4. The chapter marker is also present in the file - <!-- page:566 --> appears just before the demography section, confirming the page number I cited.
5. The slogan - "Delay the first, postpone the second and prevent the third" - also appears verbatim in the file at line 6432, which is the chapter opener Park uses for the demography chapter.

What I CAN do ✅

• Pull content directly from Park's textbook - exact text, definitions, classifications, data
• Organize it into clean, structured notes with headings, tables, and bullet points
• Create text-based flowcharts using structured formatting (arrows, boxes via markdown)
• Cover any PSM topic - Epidemiology, Biostatistics, Health Programs, Demography, Environment, Nutrition, Family Medicine, etc.
• Cross-reference multiple chapters when a topic spans sections
• Cite exact page numbers so you can verify in your physical book

What has limitations ⚠️

• Graphic/image flowcharts (actual drawn diagrams) - I can generate these as images too, but they won't have Park's content embedded visually; the text notes with structured flowcharts are more reliable for exam prep
• The library has a specific edition (ISBN 9789382219163) - if your college uses a very different edition, some page numbers may vary slightly

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Best way to ask me:

"From Park's textbook, give me detailed notes on [topic] with flowcharts"

• ISBN in the library: 9789382219163
• Publisher: Banarsidas Bhanot
• Likely edition: 26th edition (2021)
• Current latest edition: 28th edition (2023)

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Dog Bite with Bleeding - No Previous Vaccination

Park's Textbook of Preventive and Social Medicine, Chapter on Rabies (p. 324-325)

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1. CATEGORY OF BITE (2 marks)

Street dog bite with bleeding = transdermal wound = Category III

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2. MANAGEMENT OF THIS CASE (8 marks)

STEP 1: LOCAL WOUND TREATMENT (First & Most Important)
           ↓
STEP 2: RABIES IMMUNOGLOBULIN (Passive Immunization)
           ↓
STEP 3: ANTI-RABIES VACCINE (Active Immunization)

STEP 1 - Local Treatment of Wound

"Animal experiments have shown that local wound treatment can reduce chances of developing rabies by up to 80%"

• Immediate flushing and washing with plenty of soap and water
• Under running tap for at least 15 minutes
• For punctured wounds - use catheters to irrigate
• If soap unavailable - flush with plenty of water as first-aid

• Irrigate with virucidal agents:
  • Alcohol (400-700 ml/litre), OR
  • Tincture of iodine, OR
  • 0.01% aqueous solution of iodine / povidone iodine

• Bite wounds should NOT be immediately sutured
• Suturing increases trauma and spreads virus to deeper tissues
• If suturing is necessary - do it 24-48 hours later, with minimum stitches, under cover of rabies immunoglobulin locally

• Apply antibiotics when indicated
• Give anti-tetanus procedures as appropriate

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STEP 2 - Rabies Immunoglobulin (RIG) - Passive Immunization

• Given only once, at or as soon as possible after initiation of post-exposure vaccination
• NOT indicated after Day 7 (because active antibody response is presumed to have occurred)

• All RIG should be infiltrated into and around the wound site
• Remaining RIG (if any) = inject intramuscularly at a site distant from vaccine
• Note: Equine RIG carries small risk of anaphylaxis (1/45,000 cases); skin test NOT required

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STEP 3 - Anti-Rabies Vaccine (Active Immunization)

Route A: Intramuscular (IM)

Day 0 → Day 3 → Day 7 → Day 14 → Day 28
  ↑
(also give RIG on Day 0)

• 1 IM dose (1.0 ml or 0.5 ml depending on vaccine) in deltoid (or anterolateral thigh in children <2 years)

Day 0 (2 sites) → Day 7 → Day 21

• 2 doses on Day 0 (one in each deltoid), then 1 dose each on Day 7 and Day 21

Route B: Intradermal (ID) - 2-site regimen

Day 0 → Day 3 → Day 7 → Day 28
(0.1 ml at 2 sites on each day; Day 14 is skipped)

• Animal proved rabies-free by lab examination, OR
• Domestic dog/cat/ferret remains healthy throughout a 10-day observation period from date of bite

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3. PRE-EXPOSURE PROPHYLAXIS (PrEP) (5 marks)

"PrEP is recommended for anyone at increased risk of exposure to rabies virus" - Park's

Who Should Receive PrEP?

High-risk groups for PrEP
├── Continual risk
│   ├── Laboratory workers handling rabies/lyssavirus
│   └── Periodic antibody testing every 6 months
├── Frequent risk
│   ├── Veterinarians
│   ├── Animal handlers
│   └── Antibody monitoring every 2 years
└── Increased/Occasional risk
    ├── Travellers with extensive outdoor exposure
    └── Children living in rural high-risk areas

PrEP Schedule

Booster Doses

• Routine boosters NOT required for those who completed primary PrEP series, unless occupation puts them at continual/frequent risk
• Booster recommended only if rabies virus neutralizing antibody titre falls to < 0.5 IU/ml
• Antibody testing preferred over routine boosters where available

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4. HEALTH EDUCATION FOR PREVENTION (5 marks)

A. Community Education

PUBLIC EDUCATION
      │
      ├── Report animal bites IMMEDIATELY to health authorities
      ├── Do NOT handle stray/sick animals
      ├── Seek immediate medical care after any bite
      └── First aid - wash wound with soap and water for 15 min

B. Dog Owner Education

• Registration and licensing of all domestic dogs
• Restraint of dogs in public places
• Ensure regular vaccination of pet dogs
• Immediate reporting if pet dog shows abnormal behavior
• Immediate destruction of dogs/cats bitten by rabid animals
• Quarantine for ~6 months of imported dogs

C. Education on Animal Bite Response

D. Animal Control Awareness

• Support mass immunization of dogs (at least 80% of dog population must be covered)
• Support elimination of stray and ownerless dogs
• Understand that dogs are the source of 99% of human rabies infection

E. School/Children Education

• Children <15 years are most commonly bitten
• Teach children: never tease, corner or approach stray dogs
• Report any animal contact/bite to a parent or teacher immediately

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Key Exam Point: Rabies is the only communicable disease of man that is always fatal once symptoms appear - hence prevention and prompt PEP are absolutely critical.

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Smoking & Lung Cancer Study - Mr. Shiv Shankar

Park's Textbook of Preventive and Social Medicine, Chapter on Epidemiology, pp. 89-91

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1. STUDY DESIGN - IDENTIFICATION & JUSTIFICATION (3 marks)

The study is a PROSPECTIVE COHORT STUDY (also called Longitudinal / Incidence / Forward-looking study)

Justification:

DIRECTION OF STUDY:

PAST ←————————————— PRESENT ——————————————→ FUTURE
                        |
               Identify 2 groups:          Observe for 10 years
               • Smokers (exposed)    →    Lung cancer develops?
               • Non-smokers (unexposed) → Lung cancer develops?

               ════════════ CAUSE TO EFFECT ═══════════►

Park: "Cohort study is known by a variety of names: prospective study, longitudinal study, incidence study, and forward-looking study."

• The outcome (lung cancer) had not yet occurred when investigation began
• The study begins in the present and continues into the future

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2. ELEMENTS/STEPS TO CONDUCT THIS STUDY (7 marks)

ELEMENTS OF A COHORT STUDY
         │
         ├── 1. Selection of Study Subjects
         ├── 2. Obtaining Data on Exposure
         ├── 3. Selection of Comparison Groups
         ├── 4. Follow-up
         └── 5. Analysis

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STEP 1: Selection of Study Subjects

• When exposure is fairly frequent in the population
• Cohorts drawn from well-defined geographical/political areas (e.g., Framingham Heart Study)
• In Mr. Shiv Shankar's study: select smokers and non-smokers from general population

• Professional groups (doctors, nurses, teachers)
• Classic example: Doll's prospective study - used British doctors listed in the Medical Register of the UK in 1951 to study smoking and lung cancer
• These groups are homogeneous and easy to follow-up

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STEP 2: Obtaining Data on Exposure

• Whether they have been exposed (smoker) or not (non-smoker)
• Level or degree of exposure (e.g., number of cigarettes/day)

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STEP 3: Selection of Comparison Groups

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STEP 4: Follow-up

• Duration: 10 years (as in the scenario)
• The aim is at least 95% follow-up of all participants

1. Periodic medical examination of each cohort member
2. Reviewing physician and hospital records
3. Routine surveillance of death records
4. Mailed questionnaires, telephone calls, periodic home visits - preferably all three on an annual basis

Losses to follow-up are inevitable due to death, change of residence, migration, or withdrawal - these may bias the results

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STEP 5: Analysis

• (a) Incidence rates among exposed and non-exposed
• (b) Estimation of risk - Relative Risk and Attributable Risk

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3. BIASES IN COHORT STUDY (5 marks)

BIASES IN COHORT STUDY
        │
        ├── 1. Selection Bias
        ├── 2. Information / Observer Bias
        ├── 3. Confounding Bias
        ├── 4. Attrition / Loss to Follow-up Bias
        └── 5. Behavioural Change Bias

(a) Selection Bias

• Subjects who volunteer for the study may not represent all smokers/non-smokers in the population
• Smokers who agree to participate may be healthier than average ("Healthy worker effect")
• The comparison groups may not be truly comparable in demographic characteristics

(b) Information / Observer Bias

• Interviewer's bias: If the investigator knows who is in the exposed group (smokers), they may examine them more thoroughly for lung cancer signs
• Can be controlled by blinding the examiner to exposure status

(c) Confounding Bias

• Confounders like age, occupation, alcohol use, air pollution, socioeconomic status may independently affect lung cancer risk
• They are associated with both the exposure (smoking) and the outcome (lung cancer)
• Control: matching, stratification, or multivariate analysis

(d) Attrition / Loss to Follow-up Bias

• Over 10 years, participants may migrate, die, change behaviour, or drop out
• If smokers who develop early symptoms drop out more than non-smokers, the incidence of lung cancer among smokers will be underestimated
• Park: "losses may bias the results" - target ≥ 95% follow-up

(e) Behavioural Change Bias ("Hawthorne Effect")

• Park specifically mentions: "the study itself may alter people's behaviour"
• Being observed may cause smokers to quit or reduce smoking, leading to underestimation of the true risk
• This makes the relative risk appear smaller than it actually is

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4. OUTCOME INDICATORS (5 marks)

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(a) Incidence Rate

• Calculated directly in exposed and unexposed groups
• Using the 2×2 contingency table:

• Incidence among smokers = a / (a+b)
• Incidence among non-smokers = c / (c+d)

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(b) Relative Risk (RR)

"Relative risk is the ratio of the incidence of the disease among exposed and the incidence among non-exposed"

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(c) Attributable Risk (AR)

"Attributable risk is the difference in incidence rates of disease between an exposed group and a non-exposed group"

• AR tells us how much disease can be prevented if the risk factor is eliminated

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(d) Population Attributable Risk (PAR)

• Estimates how much lung cancer in the entire population could be reduced if smoking is eliminated
• Park's example from UK Physicians: 86% of lung cancer deaths could be avoided if cigarettes were eliminated

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(e) Statistical Significance (P-value)

• Park's example: P < 0.001 (highly significant)
• Confirms the association between smoking and lung cancer is not due to chance

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Summary Table of Outcome Indicators

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Epidemiology - Definition & Classification of Study Designs

Park's Textbook of Preventive and Social Medicine, Chapter 3 (Epidemiology), pp. 64-93

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a) DEFINITION OF EPIDEMIOLOGY (4 marks)

Etymology

Epidemiology is derived from the word "epidemic" - Epi (among) + Demos (people) + Logos (study)

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Historical Definitions (Evolution)

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Modern / Standard Definition (IEA Definition - Park)

"The study of the occurrence and distribution of health-related events, states, and processes in specified populations, including the study of the determinants influencing such processes, and the application of this knowledge to control relevant health problems."

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Three Core Components of Epidemiology

EPIDEMIOLOGY
      │
      ├── 1. DISEASE FREQUENCY
      │         • Measures frequency of disease, disability, death
      │         • Expressed as rates & ratios (incidence, prevalence, death rate)
      │         • Allows comparisons between populations
      │
      ├── 2. DISTRIBUTION OF DISEASE
      │         • Disease is NOT uniformly distributed
      │         • Studied by:
      │              a. TIME  – When is the disease occurring?
      │              b. PLACE – Where is it occurring?
      │              c. PERSON – Who is getting the disease?
      │         • Leads to formulation of aetiological hypothesis
      │
      └── 3. DETERMINANTS OF DISEASE
                • Identifies underlying causes or risk factors
                • Tests aetiological hypotheses
                • Determinants include: geophysical, biological, behavioural,
                  social, cultural, economic and political factors
                • This aspect = "Analytical Epidemiology"

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Aims of Epidemiology (as per IEA)

1. To describe the distribution and magnitude of health and disease problems in human populations
2. To identify aetiological factors (risk factors) in the pathogenesis of disease
3. To provide data essential for planning, implementation and evaluation of health services for prevention, control and treatment of disease

Ultimate aim: "To eliminate or reduce the health problem or its consequences, and to promote the health and well-being of society as a whole"

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b) CLASSIFICATION OF EPIDEMIOLOGICAL STUDY DESIGNS (5 marks)

EPIDEMIOLOGICAL STUDY DESIGNS
              │
    ┌─────────┴──────────┐
    │                    │
OBSERVATIONAL        EXPERIMENTAL
(No intervention)    (Intervention done)
    │
    ├── A. DESCRIPTIVE
    │         • Case reports
    │         • Case series
    │         • Cross-sectional studies
    │         • Ecological (Correlational) studies
    │
    └── B. ANALYTICAL
              • Case-Control Study
              • Cohort Study

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TYPE 1: DESCRIPTIVE EPIDEMIOLOGY

"Descriptive studies are usually the first phase of an epidemiological investigation"

• Concerned with observing the distribution of disease or health-related characteristics in human populations
• Asks: When? Where? Who? (Time, Place, Person)
• Purpose: Formulation of aetiological hypothesis (not testing it)

• Case reports / Case series - clinical observations of individual cases
• Cross-sectional studies (prevalence studies) - snapshot of population at one point in time
• Ecological studies - compare disease rates across populations

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TYPE 2: ANALYTICAL EPIDEMIOLOGY

"In contrast to descriptive studies that look at entire populations, in analytical studies, the subject of interest is the individual within the population. The object is not to formulate, but to test hypotheses."

(a) CASE-CONTROL STUDY (Retrospective Study)

• Both exposure and outcome (disease) have already occurred before study begins
• Proceeds backwards - from effect to cause
• Uses a control/comparison group

CASE-CONTROL STUDY DIRECTION:

PAST ←─────────────── PRESENT
(Exposure occurred)    |
(Disease occurred)     Start study here
                       │
                 ┌─────┴──────┐
                 CASES      CONTROLS
              (with disease) (without disease)
                 │              │
         Look BACKWARDS for exposure history

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(b) COHORT STUDY (Prospective Study)

• Cohorts identified before the appearance of disease
• Observed over a period of time for frequency of disease
• Proceeds forward - from cause to effect

COHORT STUDY DIRECTION:

PRESENT ─────────────────────→ FUTURE
   │
Identify cohorts:
• Exposed group   ──────────→ Disease develops? (YES/NO)
• Non-exposed group ────────→ Disease develops? (YES/NO)

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TYPE 3: EXPERIMENTAL EPIDEMIOLOGY

"Experimental or intervention studies are similar in approach to cohort studies excepting that the conditions in which study is carried out are under the direct control of the investigator"

• Involves deliberate intervention or manipulation
• Experimental group: Intervention applied
• Control group: No change made
• Outcome compared between both groups
• Contrasts with observational studies where epidemiologist only observes

• Modern experimental epidemiology = equated with RCTs
• Randomization ensures comparison groups are similar

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Summary Comparison Table

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Case Control Study Design

Park's Textbook of Preventive and Social Medicine, pp. 83-86

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c) CASE CONTROL STUDY DESIGN (7 marks)

Definition & Key Features

"Case control studies, often called 'retrospective studies', are a common first approach to test causal hypothesis."

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Direction of Study

CASE-CONTROL STUDY DIRECTION:

            PAST                          PRESENT
   (Exposure + Disease occurred)    (Study begins here)
              ←─────────────────────────────
                                           │
                                    ┌──────┴──────┐
                                  CASES        CONTROLS
                              (WITH disease) (WITHOUT disease)
                                    │              │
                         Look BACK for exposure history in both groups
                                    │              │
                         Exposed?  YES/NO    Exposed? YES/NO

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The 2×2 Contingency Table (Framework)

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FOUR BASIC STEPS IN CONDUCTING A CASE CONTROL STUDY

STEP 1: Selection of Cases and Controls
            ↓
STEP 2: Matching
            ↓
STEP 3: Measurement of Exposure
            ↓
STEP 4: Analysis and Interpretation

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STEP 1: Selection of Cases and Controls

• Diagnostic criteria: Histological/clinical criteria must be specified before the study and NOT altered during it
• Eligibility criteria: Only newly diagnosed (incident) cases within a specified time period are eligible (not old/prevalent cases)

• Controls must be free from the disease under study
• Must be as similar to cases as possible except for absence of the disease
• Number: If cases are few (<50) - use 2, 3, or even 4 controls per case; otherwise 1:1 ratio

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STEP 2: Matching

"Matching is defined as the process by which we select controls in such a way that they are similar to cases with regard to certain pertinent selected variables which are known to influence the outcome of disease."

• Associated with the exposure under investigation, AND
• Independently a risk factor for the disease

• Group matching (frequency matching): Cases stratified by age/sex/occupation; controls matched proportionally
• Pair matching (individual matching): For each case, one control matched closely on selected variables (age, sex, etc.)

Important: Never match on the suspected aetiological factor itself - this eliminates the variable you are trying to study!

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STEP 3: Measurement of Exposure

• Information obtained by interviews, questionnaires or past records (hospital/employment records)
• Must be obtained in precisely the same manner for both cases and controls
• Most important consideration: ruling out BIAS (systematic error)

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STEP 4: Analysis

• Exposure rate in cases = 33/35 = 94.2%
• Exposure rate in controls = 55/82 = 67.0%
• P < 0.001 (statistically significant)

• Discrete variables (smoking/cancer) → Chi-square test / SE of difference between two proportions
• Continuous variables (age, BP) → SE of difference between two means / t-test
• Convention: P ≤ 0.05 = statistically significant

"From a case control study, we derive Odds Ratio (OR) which is a measure of the strength of association between risk factor and outcome."

1. Disease must be relatively rare
2. Cases must be representative of all with the disease
3. Controls must be representative of all without the disease

Note: A typical case-control study cannot calculate Relative Risk directly (no population at risk/denominator) - hence Odds Ratio is used as its estimate.

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Advantages of Case Control Study

1. Relatively easy to carry out
2. Rapid and inexpensive (compared to cohort studies)
3. Requires few subjects
4. Suitable for rare diseases
5. No risk to subjects
6. Can study several aetiological factors simultaneously
7. No attrition problems (no follow-up needed)
8. Ethical problems minimal

Disadvantages

1. Relies on memory or past records - accuracy uncertain
2. Selection of appropriate control group is difficult
3. Cannot calculate incidence or relative risk directly
4. Not suitable when exposure data is difficult to obtain from records

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d) BIASES IN CASE CONTROL STUDY (4 marks)

"Bias is any systematic error in the determination of the association between the exposure and disease. The relative risk estimate may increase or decrease as a result of the bias."

BIASES IN CASE CONTROL STUDY
              │
    ┌─────────┼──────────┬───────────┬──────────┐
    ▼         ▼          ▼           ▼          ▼
Confounding  Recall   Selection  Berkesonian  Interviewer's
  Bias       Bias      Bias        Bias         Bias

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(a) Bias Due to Confounding

• A confounding factor is associated with BOTH exposure AND disease
• Distorts the true association between the factor under study and the disease
• Example: In studying alcohol and oesophageal cancer - smoking confounds the result
• Control: Matching for confounding variables (age, sex, occupation, social status)

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(b) Memory / Recall Bias

• Cases (with disease) are more likely to recall past exposure than healthy controls
• Cases have a stronger motivation to think about possible causes of their illness
• Example: A person who had myocardial infarction is more likely to remember dietary habits/stress than a healthy control
• Results in overestimation of the exposure-disease association

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(c) Selection Bias

• Cases and controls may not be representative of cases and controls in the general population
• Systematic differences in characteristics between the two groups
• Example: Hospital controls may have diseases also associated with the exposure under study (e.g., choosing bladder cancer patients as controls when studying smoking and MI)
• Control: Best prevented at study design stage; use multiple control sources

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(d) Berkesonian Bias

• Named after Dr. Joseph Berkeson
• Arises due to different rates of hospital admission for people with different diseases
• Hospital-based cases and controls differ from those in the general population in terms of disease severity, health-seeking behavior
• Results in spurious associations or masking of true ones
• Example: If a particular disease combination leads to more hospital admissions, cases will be over-represented

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(e) Interviewer's Bias

• Occurs when the interviewer knows the hypothesis AND knows who the cases are
• May question cases more thoroughly regarding positive history of the suspected factor
• Detection: Compare average interview time for cases vs controls
• Control: Eliminated by double-blinding (interviewer does not know case/control status)

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