8 - Disease factors Flashcards
Epidemiological study
test the hypothesis of association between exposure and outcome
Risk factors
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
What is the environment?
• 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
Organism characteristics
- infectivity
- pathogenicity
- virulence
- immunogenicity
- antigenic stability
Infectivity
– Capacity to multiply in host and transmission risk
– Measured by the secondary attack rate in a household, school, etc
Pathogenicity
– Capacity to cause disease or symptoms in host
– Measured by the apparent : inapparent infection ratio
Virulence
– tendency of agent to cause severe disease
– Measured by the case fatality ratio
Immunogenicity
– Capacity to introduce specific and long lasting immunity in a host
Antigenic stability
– Can induce lifelong immunity
Host susceptibility
• Host characteristics – Age, sex, race, genetics – Religion, customs – Occupation, marital status – Previous diseases – Immune status
Herd immunity
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
Herd immunity conditions
– Disease agent must be from a single host species
– Transmission direct from one person to another
– Relies on random mixing of the population
Social environment
a) Socio-economic
b) Cultural
c) Behavioural
Socio-economic
Usually associated to level of education, income and occupation (these are often dependent to each other).
Healthy workers
- 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
Cultural
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
Behaviour
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
Occupation and health
• 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.
Effect of work on health - reasons
• Manual occupations have higher SMRs than managerial professional occupations
Direct risks at work
• Injury
• Exposure to hazardous substances
– Example: Asbestos and mesothelioma
indirect risks at work
• Stress
• Low pay
• Lack of automony
– Example: Bus drivers and bus conductors, Whitehall Study
Definition of Ageing
• For statistical purposes ageing defined CHRONOLOGICALLY
BUT
• Ageing also defined BIOLOGICALLY i.e. by physical and mental decline
3 key factors of ageing
- Global increase in PROPORTION of older people in society;
- Global decline in birth rates and reduction in no. of under 15s;
- Global decline in nos. of people of working age (15-59)
Population ageing
- Is affecting nearly all countries in the world;
* Results mainly from reductions in fertility rates (virtually universal)
Challenges of population agening
- social sphere
- economic sphere
- political sphere
- health sphere
social sphere
pop. ageing influences family composition and living arrangements, housing demand and migration trends
economic sphere
increased longevity means older pops. drawing retirement & other old age benefits for longer than in the past
political sphere
will shape voting patterns and political representation
health sphere
will impact on epidemiological patterns of health and illness, on the demand for healthcare services and the availability of informal care-givers.
implications of ageing
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.
