8 - Disease factors

Question 1

Epidemiological study

Answer 1

test the hypothesis of association between exposure and outcome

Question 2

Risk factors

Answer 2

A risk factor can be either:
– A predictor (marker or proxy)
   • Such as employment in a specific industry
 Or
– A causal factor 
   • Such as exposure to benzene at work

Question 3

What is the environment?

Answer 3

• The air we breathe
• Water we drink
• Food we eat
• Climate surrounding us
• Space around us for movement
• The biosphere
Most disease are caused by or influenced by environmental factors

Question 4

Organism characteristics

Answer 4

• infectivity
• pathogenicity
• virulence
• immunogenicity
• antigenic stability

Question 5

Infectivity

Answer 5

– Capacity to multiply in host and transmission risk

– Measured by the secondary attack rate in a household, school, etc

Question 6

Pathogenicity

Answer 6

– Capacity to cause disease or symptoms in host

– Measured by the apparent : inapparent infection ratio

Question 7

Virulence

Answer 7

– tendency of agent to cause severe disease

– Measured by the case fatality ratio

Question 8

Immunogenicity

Answer 8

– Capacity to introduce specific and long lasting immunity in a host

Question 9

Antigenic stability

Answer 9

– Can induce lifelong immunity

Question 10

Host susceptibility

Answer 10

• Host characteristics
– Age, sex, race, genetics
– Religion, customs
– Occupation, marital status
– Previous diseases
– Immune status

Question 11

Herd immunity

Answer 11

resistance of a group of people to attack by a disease
– When a large proportion of the population are immune
– Disease transmission is restricted
– Circulation of disease to susceptible people is also restricted
• Advantage is that 100% immunization not always necessary

Question 12

Herd immunity conditions

Answer 12

– Disease agent must be from a single host species
– Transmission direct from one person to another
– Relies on random mixing of the population

Question 13

Social environment

Answer 13

a) Socio-economic
b) Cultural
c) Behavioural

Question 14

Socio-economic

Answer 14

Usually associated to level of education, income and occupation (these are often dependent to each other).

Question 15

Healthy workers

Answer 15

• Overall though, the working population is healthier than the non-working population
• Because non-healthy people are selected out of work
• And those who have been harmed by work can no longer work
• Called the “healthy worker effect” and is a type of selection bias

Question 16

Cultural

Answer 16

E.g. ethnicity, religion, place of residence.
Ethnic and racial differences in inflammatory bowel disease have been observed (low incidence in Asian Americans compared to white Americans).
Iranian students who engaged more often in organized religious activities and had higher intrinsic religiosity were less likely to engage in risky behaviours such as sexual risk taking, careless driving, violence, smoking, along with alcohol and drug abuse

Question 17

Behaviour

Answer 17

Marital and employment status are associated with more favourable health outcomes in high-income countries.
Obesity, smoking, drinking alcohol, unsafe sex, illicit drugs, violence, accidents

Question 18

Occupation and health

Answer 18

• Occupational mortality is death from work-related causes
– Social class and occupation closely related, but not interchangeable
• The Whitehall study of British civil servants begun in 1967.

Question 19

Effect of work on health - reasons

Answer 19

• Manual occupations have higher SMRs than managerial professional occupations

Question 20

Direct risks at work

Answer 20

• Injury
• Exposure to hazardous substances
– Example: Asbestos and mesothelioma

Question 21

indirect risks at work

Answer 21

• Stress
• Low pay
• Lack of automony
– Example: Bus drivers and bus conductors, Whitehall Study

Question 22

Definition of Ageing

Answer 22

• For statistical purposes ageing defined CHRONOLOGICALLY
BUT
• Ageing also defined BIOLOGICALLY i.e. by physical and mental decline

Question 23

3 key factors of ageing

Answer 23

1. Global increase in PROPORTION of older people in society;
2. Global decline in birth rates and reduction in no. of under 15s;
3. Global decline in nos. of people of working age (15-59)

Question 24

Population ageing

Answer 24

• Is affecting nearly all countries in the world;

* Results mainly from reductions in fertility rates (virtually universal)

Question 25

Challenges of population agening

Answer 25

• social sphere
• economic sphere
• political sphere
• health sphere

Question 26

social sphere

Answer 26

pop. ageing influences family composition and living arrangements, housing demand and migration trends

Question 27

economic sphere

Answer 27

increased longevity means older pops. drawing retirement & other old age benefits for longer than in the past

Question 28

political sphere

Answer 28

will shape voting patterns and political representation

Question 29

health sphere

Answer 29

will impact on epidemiological patterns of health and illness, on the demand for healthcare services and the availability of informal care-givers.

Question 30

implications of ageing

Answer 30

We need to:
• develop and focus on health promotion and programmes designed to support active ageing;
• plan for different forms of healthcare services designed to meet the needs of diseases of older age;
• plan for certain types of health professionals with the necessary skills to treat diseases of old age;
• develop different forms of care and financing of healthcare.