Week 1 Flashcards
Incidence
the number of new cases in a specific time period
prevalence
the number of existing cases at a given time
epidemiology
The study of the distribution of disease and its determinants
- from “epidemic”
Epidemiological Transition: The stages
- Age of pestilence and famine
- high death rates and birth rates - Receding pandemics
- low death rates, but high birth rates - Degenerative and chronic diseases
- low death rates and low birth rates
Early health improvements
- improvements in water and sanitation (England and Wales mid-19th century)
- immunisation (early 20th century)
- antibiotics (mid 20th century)
disease patterns - developed countries
- low birth rates
- rectangular population pyramid
- predominantly chronic diseases, which are decreasing
disease patterns - low mortality developing countries
- lower death rates
- high birth rates
- population pyramid becoming rectangular
- double burden of disease (infectious and chronic)
population health
The health outcomes of a group of individuals, including the distribution of such outcomes within the group
What has fuelled the epidemic of chronic diseases?
- the globalisation of risk
- the transmission of unhealthy behaviours has proceeded with great rapidity to developing countries
- countermeasures are absent - both at a policy level and a sophisticated population/public health infrastructure
The globalisation of risk
- governments have underdeveloped: policy responses, health and public health systems
- economic development usually the priority even before people - uneven wealth distribution
- political and geographic boundaries cannot cope with modern communications where ideas and culture rapidly transfer
- demands a global response: regulation international trade, share and disseminate interventions, policies on recruiting professionals
Primordial Prevention
actions or measures that inhibit the emergence and establishment of environmental, economic, social and behavioural conditions, cultural patterns of living, etc. known to increase the risk of disease
primary prevention
- protection of health by personal or communal efforts, such as enhancing nutritional status, immunising against communicable diseases and eliminating environment risks
- alteration of susceptibility or reduction of exposure of susceptible individuals
secondary prevention
- a set of measures available to individuals and communities for the early detection and prompt intervention to control disease and minimise disability
- early detection and treatment of disease
tertiary prevention
- measures aimed at softening the impact of long-term disease and disability by eliminating or reducing impairment, disability and handicap; minimising suffering and maximising potential years of useful life
- alleviation of disability resulting from disease and attempts to restore normal functioning
What is a risk factor?
Presence of a behaviour or physiological parameter that increases the chances of having “heart disease”
- no single factor causes heart disease
A risk factor must be:
- associated with a disease - greater exposure, greater risk
- make sense in a biological way
- reducing risk factor reduces disease
Sir Geoffrey Rose: The strategy in Rose’s time
- a clinical strategy - physician strategy
- people were sick and became patients
- interventions usually when the disease was entrenched and often well advanced
- prevention was not as important a concept
- sometimes patients are created e.g. high blood pressure
- public health strategies were educational and addressed those at risk
what do we conclude?
- we need to be able to observe at population levels not just individual levels
- to find the determinants of incidence and prevalence rates, we need to study the characteristics of populations, not characteristics of individuals
- accepted normal values may not be normal and they may not be okay
- curves of risk can be shifted
High risk (HR)
the relative risk of death is high due to the presence of the risk factor or the disease process
- there are far fewer people in the HR group - the majority are not in the HR group
Absolute risk
while the actual # of deaths is high in the HR group it accounts for very few of the population deaths due to this disease or risk factor
- a large number of people exposed to a lesser or moderate risk leads to the majority of cases in population
The case for a population strategy
- if our health system focuses only on those who are at high risk or are sick; if we employ only clinical strategies we will miss the majority that contribute most to the overall mortality
- a population preventive strategy that seeks to move the entire population distribution curve to the left is essential
- therefore a community (society) that wishes to make an impact on a disease or condition must imply a two pronged strategy - a high risk, clinical intervention accompanied by a population strategy to influence the segment that accounts for the majority of the cases
A population prevention strategy
An intervention which brings much benefit to the population offers little benefit to each participating individual
- control the determinants of incidence
- lower mean levels of risk factors
- shift the distribution of exposure in a more favourable direction
- the mechanisms - mass environmental controls and alter social norms of behaviour
A population strategy - advantages
- large potential for the population
- behaviourally appropriate
A population strategy - limitations
- a small benefit to each participating individual - this is the “prevention paradox”
- poor subject motivations
- poor physician motiviation
- benefit-risk ratio problematic to demonstrate - potentially costly
The population approach
- both populations and high risk groups
- creates environments supportive of health
- focuses on health promotion and disease prevention
- works through partnerships and coalitions
- includes intersectoral and interdisciplinary groups and organisations
- uses healthy public policy development and community mobilisation as major tools
Rose has lead us to an understanding of?
- observing populations to understand cause of incidence and prevalence is essential
- normal is not necessarily okay
- risk distribution at a population level can be improved (move the curve)
- most cases do not arise from the high risk group
- to improve health need a population health strategy to complement a high risk strategy
