Epidemiology defn
-The study of distribution and causes of health and illness in human populations
•And factors that influence or determine this distribution
Premise of epidemiology
Disease occurrence (or its outcome) is NOT random but can vary depending on a variety of characteristics and predisposing factors.
Incubation period
- Time between exposure to an infectious agent and onset of symptoms
- Varies based on dose, route, replicate rate, host responses
Epidemic defn
The occurrence in a community or region of cases of an illness or health-related event clearly in excess of normal expectancy
Timeline of Infectious Disease
- Infection (pathological onset)
- Incubation period
- - clinical disease phase begins – - First symptoms
- Diagnosis
- Outcome
Top 6 Causes of Death in Children
1) Malnutrition
2) Other
3) ARI
4) Diarrhea
5) Measles
6) Malaria
Prevalence rate per 1,000 (formula)
(no. of cases of disease present in pop. at specified time) / (no. of persons in pop. at specified time) x 1000
Incidence rate per 1,000 (formula)
(No. of new cases of disease in pop. during specified period of time) / (Number of persons exposed to risk of developing disease during that period of time) x 1000
Artifactual (Reasons for Change in Mortality Trends of Disease)
- Errors in numerator
• Due to classification of disease
• Due to accuracy in reporting death - Errors in denom.
•Errors in enumeration of pop.
Real (Reasons for Change in Mortality Trends of Disease)
•Changes in age distribution •Changes in survivorship •Changes in incidence of disease - Genetic factors - Environ. factors
What are the different Agents of disease?
1) Nutritive elements
2) Chemical agents
3) Physical agents
4) Infectious agents
Environmental factors
1) Physical environment
2) Biologic environment
3) Socioeconomic environment
What is the triangle for toxins?
Agents Environment Host
What is a retrospective study?
Using data from the past during a current study (looking backward)
What are host factors?
- Genetics
- Age
- Sex
- ethnic group
- physiologic state
- prior immunologic experience
- intercurrent or preexisting disease
- human behavior
prospective cohort study
Collects data on exposure at initiation of study & follows population in order to observe the occurrence of health outcomes at some time in future
historical prospective study
- Identify cohort defined in past on basis of existing stuff from past
- Classify individuals in cohort.
- Determine on basis of existing stuff from past, classify individuals in cohort
- Determine whether disease has developed before now or follow into future evaluating
Analytical vs. Descriptive (Epid. studies)
Analytical
- Case control
- Cohort
- Clinical trials
Descriptive
- Morbidity
- Mortality
Air pollution defn
the presence in the air of one or more contaminants or combinations of contaminants that can be injurious to human, animal, plant life, property, and interferes with normal conduct of business
air pollutant defn
- Substance in the air which adversely alters the environment by interfering with the health, the comfort, or the food chain, or by interfering with the property values of people.
- Can originate from natural or anthropogenic source.
- Ex) Acid rain, ozone, smog
Weaknesses of indirect studies
- Possibility of indirect association
- Interpretation of negative results
- Often look at agents one at a time
- Comparability of data by place and time
- Mobility problem
Observational vs. Experimental studies
- Observational is more data aggregation and analysis
-Use that to build a hypothesis - Then you can do an experimental study based on that
this which will lead to more studies in future
What is the problem?
- Small particulates from fossil fuels
- Indoor smoke
