Bms 1042 Notes

BMS1042

LECTURE 1

Learning objectives

• Understand the public health issues that surround you

• Be able to identify the main areas of public health in a current and historical context

• Know the difference between cause and association – Introduction to Bradford Hill Criteria

Public health issues

• Alcoholism
• Obesity
• Allergies and intolerance
• Antibody resistance
• Smoking
• Ice epidemic
• Mental health

The practice of public health aims to:

• Improve the health of an entire population
• Reduce health inequalities in a population
• Step beyond the individual-level focus of mainstream medicine

IMPORTANT TOOLS: EPIDEMIOLOGY & BIOSTATISTICS

Epidemiology is the branch of medicine, which deals with the incidence, distribution, and possible control of diseases and other factors relating to health  

John Snow & the Broad Street pump

• Tracking and surveillance to prevent an epidemic  
• Outbreak investigation
• Cholera, tracking of the original source (the well) to prevent further contamination/ disease outbreak

CAUSATION

• Statistics can be manipulated to not show causation but correlation
• There is usually not one single cause for any disease

CAUSATION; SUFFICIENT & NECESSARY

• A risk factor is sufficient, if the presence of this factor alone is enough to result in the disease
• A risk factor is necessary if the disease is never present when the factor is not present

NECESSARY BUT NOT SUFFICIENT

To get tuberculosis it is necessary to be exposed to Mycobacterium tuberculosis but the exposure in itself is not sufficient for the disease state to occur

NEITHER NECESSARY NOR SUFFICIENT

Cigarette smoking is neither necessary nor sufficient for the development of lung cancer

NECESSARY AND SUFFICIENT

A necessary and sufficient cause of Ebola Fever is the Ebola virus.

A necessary and sufficient cause of Huntington’s chorea is the genetic mutation that causes this condition (dominant)

SUFFICIENT BUT NOT NECESSARY

Decapitation is sufficient for death, but death is not necessarily caused by decapitation

FACTORS IN CAUSATION (RISK FACTORS)

Few diseases have a single cause hence there are common ‘risk factors’

• Pre-disposing: age, sex
• Enabling (disabling): low income, poor nutrition
• Precipitating: exposure to a disease agent (organisms, bacteria, viruses)
• Reinforcing: repeated exposure (radiation, constant re-exposure)

Risk factors are used to describe factors associated with the disease (e.g. smoking, lung cancer)

CAUSATION-ESTABLISHING EVIDENCE

• Temporal relationship: exposure occurs before disease (cause must precede effect)
• Plausibility: consistent with other knowledge (but other evidence may just be lacking)
• Consistency: Several studies giving the same finding
• Strength of association: What is the relative risk (a weak relationship does not mean a factor is not casual, e.g. smoking) (relative risk/risk ratio and odds ratio - quantitative)
• Dose-response: Increases exposure = increased outcome
• Reversibility: remove exposure = no outcome
• Strength of study design (advantages and weakness of studies)

If there is an association between a possible cause and an effect, it could be due to bias, confounding, casualty of the relationship, and result of chance.

COMMUNICABLE DISEASES

• Are infectious/ contagious diseases
• Measles, smallpox, Spanish flu, HIV/AIDS, Typhus, Chloera, Black death

NON-COMMUNICABLE DISEASES

• Diseases that is non-infections and non-transmissible among people
• Cardiovascular diseases, cancer, chronic respiratory disease, etc.
• Leading causes of death and diseases worldwide

NCD PREVENTION

1. Tobacco control
2. Promoting sensible alcohol consumption
3. Improving nutrition
4. Encouraging physical activity

• Smoking is the epidemic of the 20th century
• Injuries are the principal cause of death in almost half of the people under 45 years of age
• Factors that may influence road safety or drowning (directly & upstream perspective)

EPIDEMIOLOGY IN PROFESSIONAL LIFETIME

• Emerging infectious diseases
• Changing lifestyles and behaviors
• Impact of climate change

• Direct (impact on coastal communities)
• Indirect (food water, social, economic) effects
• Temperature change (heat waves, storms, floods)
• Nutrition and food security (crop yields)
• Water availability and quality
• Air quality (pollutants, aeroallergens)
• Vector, rodent and bird-borne diseases
• Exposure to UV radiation

LECTURE 2

PUBLIC HEALTH BY NUMBERS

• Understand enough biostatistics to be able to make sense of the contents of journal articles – this will be useful for subsequent years of the course.

• Be able to do simple statistical analysis.

• Be more critical of how public health is reported in the media.

Importance of biostatistics in public health

• Biostatistics is the science of statistics applied to the analysis of biological or medical data
• Biostatisticaians analyse data, give advice to others in research units, sample size calculations, randomization of schedule – topics such as cardiac surgery, antenatal care, breast cancer etc.
• Biostatistics and Epidemiology go ‘hand in hand’ in public health
• Good data analysis involves good data

Classification of data into types of data

[pic 1]

WHAT TYPE OF GRAPH, SUMMARY STISTICS, ANALYSIS? – Wrong identification of the type of data may result in the wrong analysis being done

TYPES OF DATA

• Categorical

– Nominal (order of categories doesn’t matter) e.g. Blood group (A, B, O, AB) e.g. Diabetic (Yes / No) Also known as “binary”