Measuring and Describing disease Flashcards
defn epidemiology
the study of the ____ and ____ of health-related states/events in _____, and the _____ of this study to the control of ______
(how often diseases occur in different groups of people and why)
the study of the distribution and determinants of health-related states/events in specified populations, and the application of this study to the control of health problems
simple defn :(how often diseases occur in different groups of people and why)
Stages of epidemiologic transition?
1- pestilence and famine - birth rate and death rate 1800s
2- receding pandemics: crude death rate falls- population size increases
3- degenerative and man-made diseases- crude brith rate falls : obesogenic environment
4- delayed degenerative diseases and emerging infections
- threat of zoonosis
- inequalities between and within countries
exposure
variable
outcome
health outcome like mortality at 5 years
population pyramids
triangle : rapidly growing : youthful population
pentagon : straight sides - stationary = more people living to old age
contracting shape : widest at top , older age groups = low brith rate
zero growth : pentagon with wider at top : spain
types of exposures?
drug, behaviour, demographic characteristic
what problems were faced in the pestilence and famine era?
urbanisations
constraints on food supply
high birth and high mortality rates
life expectancy low at birth
life expectancy
expected age to live at birth
life span
how long you actually live not average of the population
receding pandemics are defined by?
Agricultural development improves nutrition
Water, sanitation, hygiene
Vaccination emerges
High birth rate and reducing mortality
Life expectancy increasing
degenerative and Man-Made diseases
Lifestyle factors and NCDs predominate: cancer and CVD
Environmental and global determinants drive obesity and other risk factors
Technology reduces need for physical labour
Addiction, violence and other issues emerge
delayed degenerative diseases and emerging infections
hybristic
Health technology defers morbidity, albeit at increasing financial cost
Emerging zoonotic disease presents new threats
Inequalities within and between countries come to the fore
DALY
Disability Adjusted Life Years
The DALY is a measure of disease burden that combines years of life lost from ill-health, disability or premature death. Like any other epidemiological measure, it’s not perfect, but it tells us a story.
3 groups of conditions ?
NCD
Communicable diseases
and Injuries
15-49.
What’s the leading cause of morbidity (using DALYs as the measure)?
back pain
Which cause of death accounts for the greatest modifiable behavioural risk among 15-49 year olds?
Drugs
odds
The ratio of the probability (P) of an event to the probability of its complement (1-P)
discrete data only
disease/ no disease
Prevalence
The proportion of individuals in a population who have the attribute at a
specific time point
Cumulative Incidence
New events ; people that already have it cannot be included in numerator or denominator
has no units
what are drawbacks of cumulative incidence?
follow up is needed
same for all participants and no new participants can enter study population
competing risk : cannot be assessed if follow up lost due to death etc
incidence rate
new cases at a specific time, person time allows for loss to follow up
prevalence drawbacks
with disease/ total number of people in population
proportion - at a specific time
no info on new/developing cases
Less helpful in diseases of short duration and causal inference
use of prevalence
assess’s health of a population
monitor trends over time
enable planning of health services and healthcare resources
standardisation
why?
We want to understand whether the difference in incidence might be down to their different demography: sex and age.
Direct standardisation –
this gives a similar incidence - eg. 120 strokes per 100k/yr
unwarranted variation
explained variation
statistical artefact
Hospital A is dangerous – unwarranted variation.
Hospital A has a higher risk blend of procedures and therefore may have higher frequency of deaths - explained variation.
Hospital A is better at recording deaths than other hospitals; deaths outside hospital can be difficult to establish / link – statistical artefact.
Standardised Mortality Ratio (SMR)
can be calculated by dividing the observed count by the expected count
We observed (O) 43 deaths We expected (E) 26 deaths
Therefore the O:E is 43/26 = SMR = 1.65
Alternatively we can present this as 165
Standardised moratlity ration
standardised incidence ration
SHMI data for hospital performance identifying hospitals that report higher than expected mortality
Standardised mortality ratio (SMR<75) as a marker of healthy life expectancy
granular data?
individual-level patient data
aggregated datasets
ecological studies
top-level outcomes for a population- how many people died in crude numbers rather than who died
