PSM • CHAPTER 01
PRINCIPLES OF EPIDEMIOLOGY
High-Yield NEET-PG + INI-CET
The Student’s Guide to Disease Measurement
Epidemiology vs Clinical Medicine
1. Macro vs Micro Approach
Clinical medicine focuses on individual patients, while epidemiology focuses on populations. Both approaches are complementary and essential in healthcare.
Physician treats one patient. Epidemiologist prevents disease in thousands.
Group vs Individual Approach
| Epidemiology | Clinical Medicine |
|---|---|
| Population-based study | Individual patient care |
| Prevention focus | Treatment focus |
| Community level | Hospital level |
| Studies patterns | Diagnoses disease |
2. Disease Determinants
- Biological: Age, Sex, Genetics, Immunity
- Environmental: Climate, Pollution, Housing
- Social: Lifestyle, SES, Education
Disease = Interaction of multiple determinants
3. Ratio, Proportion, Rate
- Ratio: Numerator NOT part of denominator
- Proportion: Numerator part of denominator
- Rate: Ratio + Time factor
Rate shows motion (dynamic), not just count.
4. Incidence vs Prevalence
| Incidence | Prevalence |
|---|---|
| New cases | Total cases |
| Measures risk | Measures burden |
| Time-based | Snapshot |
Prevalence = Incidence × Duration
5. Mortality Rates
- Crude Death Rate
- Specific Death Rate
- Standardized Death Rate
Specific rate is more useful than crude rate.
6. Advanced Metrics
- CFR: Severity
- Survival Rate: Prognosis
- PMR: Relative importance
RISK → Incidence
BURDEN → Prevalence
SEVERITY → CFR