PPS Epidemiological Approach to Health and Disease Flashcards
Define epidemiology
The study of the distribution and determinants of health and disease in human populations
Define public health
The science and art of: - prolonging life - preventing disease - promoting health (in the population) by the organised efforts of society
- Donald Acheson 1998
What is the value in studying health and disease in populations? (6 points)
- Measuring burden of disease
- -> impact on mortality and morbidity - Understanding who is at risk of disease
- -> which groups are afflicted, certain ages, genders, ethnicities, locations - Identifying the causes of disease
- How to prevent disease
- Identifying effective treatment for particular diseases
- Managing disease optimally in the population- how treatment services should be organised for the population
What is the clinical iceberg phenomenon?
When looking at medical care consultations to understand how much morbidity is caused by a condition need to understand a lot of it is never reached by doctors (we know = more severe, we don’t know = less severe)
What does the clinical iceberg phenomenon mean for doctors?
There is more unknown disease than known disease, this tends to be milder than known disease and therefore doctors:
- underestimate the amount of disease
- overestimate the severity of disease
Therefore to assess TOTAL amount of disease, need survery of wider population and not just those seeking care
What is involved in ‘measuring the burden of disease’?
How much impact do different illnesses have on health and disease? – needs to be assessed at population level
- impact on mortality (deaths)
- impact on morbidity (ill-health)
Different conditions cause different amounts of morbidity and mortality
(which diseases are major causes of mortality, eg cancer (neoplastic disease) and for morbidity, how much people consult doctors about certain conditions)
What is involved in ‘understanding who is at risk of disease’? And why is this important?
Understanding if a disease affects particular individuals and population groups.
- does it occur in particular PERSONS?
- does it occur in particular PLACES?
- does it occur in particular PERIODS (OVER TIME)?
Why is this important?
- helps clinicians in making diagnoses
- helps in understanding causes of disease
How can disease vary between persons?
Age, gender, social class and ethnic origin (also places and periods)
eg. Coronary heart disease mortalitiy higher in older males
What is involved in ‘identifying the causes of disease’?
A CAUSE is a factor which increases the risk of disease occuring
To show that something is a cause of disease, need evidence that exposure (to something) is associated withdisease:
Need one or more comparative studies, based in the population, to ask:
(a) is exposure associated with increased risk of disease (compared with unexposed)?
(b) do people who have the disease have increased previous exposure (compared with people without disease)?
What is in involved in ‘preventing disease’?
Once an important cause of disease is known we need to reduce exposure to these causes in order to prevent disease occurance
What is involved in ‘identifying effective treatment for particular diseases’?
Randomized controlled trials RTCs provide strong evidence of whether treatment are effective or not (eg examining effects of dexamethasone in patients hospitalised with Covid-19 showed mortality rate 20% lower compared with controls, thereby radical effect on outcome)
What is involved in ‘managing disease optimally in the population’?
How health services should be organized to provide effective treatment efficiently, fairly and at the lowest possible cost
Ensure all the people who can benefit from a beneficial intervention are receiving it (if no, who is not doing so?)
eg. found effective medications for post MI patients but only given to small proportion of people
See if:
Anyone is receiving ineffective or harmful interventions
Health provision can be improved/optimized
When is the population approach needed?
Always helpful but the more widespread the condition and its causes in the population, the more crucial the population perspective
e.g. Pandemic infections (Covid-19 etc) Coronary heart disease Type 2 diabetes Obesity Hypertension Road traffic accidents Most cancers Suicide/mental health challenges
How does the public health process work?
Begins with epidemiological base:
Understand HOW MUCH disease is present
How disease is DISTRIBUTED
What CAUSES the disease
Then how can disease be PREVENTED (via health policy and health promotion)
Then how can disease be effectively TREATED
1. EFFECTIVENESS OF TREATMENT
2. ORGANISATION OF TREATMENT
Via health service organisation
What is the purpose of clinical epidemioogy?
Application of epidemiological methods in clinical practice informs understanding of:
DIAGNOSIS: likely cause of symptoms? is a diagnostic test valid?
CAUSES: why did this patient get this diagnosis at this time in this society?
CONSEQUENCES: what is the prognosis, and what factors affect it?
TREATMENT: what treatment is effective for this patient?
What is the first step in the ‘population approach’?
MEASURING HEALTH + DISEASE IN THE POPULATION
The number of disease cases in the population is a useful starting point, but also need to define DISEASE RATES in population because they link the number of cases to population from which cases come
What are disease rates?
They link individual cases of disease to the underlying population at risk
Rate = No. of cases/Population at risk
(sometimes over a defined period of time- new events like a new case of disease oa a death)
Why is it important to relate cases of disease (numerator) to an underlying population at risk (denominator)?
Making judgements solely on numbers of cases, without considering underlying populations at risk, can lead to misleading judgements
What is the incident rate?
Occurance of new cases of disease
IR = number of new cases/population at risk
In a specific time period (eg year)
What is the prevalence rate?
Proportion of people that have an illness, presence of disease (new and old)
PR = number of new and old cases/population at risk (proportion)
What is the mortality rate?
Occurance of deaths
MR = number of new deaths/population at risk
In a specific time period (eg year)
What is the difference between disease rates and disease risks?
Both relate the number of cases of disease to an underlying population (and give similar information), but the time element is expressed slightly differently in a rate and a risk
A disease RATE expresses events/population/time
A disease RISK is a statement of probability (a simple proportion)
Mortality rate for COVID-19 (June 2020) –> 53.0 per 100,000 persons per month
Monthly Mortality risk for COVID-19 (June 2020) –> 53.0/100,000 (= 0.00053)
for risk put time ‘monthly’ in title
What are some major public health challenges in the UK?
Chronic diseases in later life, causing mortality and morbidity
Coronary disease, stroke, cancer, dementia, respiratory disease
Musculoskeletal problems, visual and hearing problems - older ppl
Mental health problems – social isolation, depression especially in older people
Accidents (especially road traffic accidents) and violence - younger ppl
Infections including Covid-19, tuberculosis, HIV, food poisoning, STD
Asthma, Preterm birth, perinatal mortality - younger
Epidemics of obesity and type 2 diabetes
What are some behaviours influencing health?
diet patterns cigarrette smoking high alcohol intake physical inactivity sexual behaviour
What are some factors in health inequalities?
social
geographic
ethnic
gender
