BMS1042 Lecture Notes - Lecture 2: Summary Statistics, Confounding, Intracranial Pressure
20 Jun 2018
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INJURY
Injury is a major cause of many deaths and physical, cognitive and psychological disabilities that
seriously affect the quality of life of injured individuals and their families. It remains a primary
cause of death in people under 45 years of age, and a leading cause of death, illness and
permanent disability in older age groups. As a result it is also a major source of health care
costs.
Many injuries are preventable, and there are substantial opportunities to reduce the incidence,
impact and burden of injury on health, using effective and innovative strategies. For the next two
weeks you will be learning about the National Health Priority Area, injury prevention and control.
3. INJURY AS A SIGNIFICANT PUBLIC HEALTH ISSUE
Identify the public health definition of injury and its classification
Public health is focused on accident prevention as opposed to injury prevention. The logic goes:
If you can understand what led to the accident, then you can intervene to that circumstance and
reduce future events. It’s a non victim-blaming mindset whereby the victims are not fully
responsible for their accidents. Rather, accident prevention needs to come from systemic
changes.
An understanding of descriptive epidemiological concepts and terms
The first stage of every descriptive epidemiologic investigation is the same. First, we need to
describe the disease distribution by characteristics relating to time, place, and the people
infected.
Once you have the who, what, where, and when, you need to start defining your population at
risk. These people are potentially susceptible
to the disease being studied, and can be
categorised by demographic, geographic, or environmental factors.
Ability to distinguish between different death rates
Mortality
is a measure of the number of deaths. This is great, because deaths are reported all
the time. However, mortality is uninformative as it does not tell you anything about the
population. Nobody dies from arthritis, yet arthritis has a big impact on the population. Mortality
fails to give us the incidence of a disease (new cases occurring), or whether or not a cure is
working to prevent the disease. Thus, mortality is restricted in the sense that it cannot capture
the “hows” of a death or the issues surrounding the death; it merely notes the death.
A much more useful measure of disease-impact on a population is morbidity.
Morbidity:
Any departure, subjective or objective, from a state of physiological or psychological
well being. This includes any disabilities, which can use measures such as incidence,
prevalence, hospital discharge, work loss days, and restricted activity days.
Case study: Lead poisoning is 100% preventable, and yet, people are dying from it. Most lead
poisoning comes from paint in the house, or kid’s toys. There are no safe levels of lead in the
body. It causes damage to the nervous system, slowed growth and development, learning and
behaviour problems, and hearing/speech problems.
Ultimately, these symptoms would result in a lower IQ, decreased focus, and underperformance
at school.
Incidence
is a measure of new cases of a disease, or the frequency of a disease over time
.
Incidence can be expressed as a rate or a risk.
Incidence rate = #new cases/ total person-time of observation
*Can range from 0-infinity
Cumulative Incidence (risk) = # new cases over specific time/ #healthy subjects at the start of
the follow up.
*Can range from 0-1
Person-time is the length of time they were at risk before actually contracting the disease. This
gives us an indication of how quickly the disease is spreading.
1 person disease-free for 1 year = 6 people disease-free for 2 months
Prevalence is the number of existing cases
at a given time, or the frequency of an existing
disease at a given period
.
Prevalence = # existing cases in the population/ # persons in a population.
Incidence and prevalence has a relationship. If we have a stationary population where the
prevalence is low, we can say that:
Prevalence = incidence rate x average duration of disease.
An overview of DALYs and QALYs
Potential years of life lost (PYLL)
Quality adjusted life years (QALYs)
Disability adjusted life years (DALYs)
Years of life lost (YLL)
Years lost to disability (YLD)
PYLL is a measure of health expectancy, or the number of years of potential life lost if they die
before a certain age. For example, if your life expectancy is 80, and you died in a car accident at
35, your PYLL is 45.
QALYs is a measure of weighing to your quality of life; each year is given a weight mark from 1
(perfect) to 0 (dead). For example, if you have a stroke, the next 10 years of your life will be as
good as 5 healthy years (0.5 weighting to 10 years).
Document Summary
Injury is a major cause of many deaths and physical, cognitive and psychological disabilities that seriously affect the quality of life of injured individuals and their families. It remains a primary cause of death in people under 45 years of age, and a leading cause of death, illness and permanent disability in older age groups. As a result it is also a major source of health care costs. Many injuries are preventable, and there are substantial opportunities to reduce the incidence, impact and burden of injury on health, using effective and innovative strategies. For the next two weeks you will be learning about the national health priority area, injury prevention and control: injury as a significant public health issue. Identify the public health definition of injury and its classification. Public health is focused on accident prevention as opposed to injury prevention.
