Flashcards in Lectures 3&4 - The importance of evidence in the practice of medicine part 2 & Global patterns of disease part 1 Deck (31)
what is epidemiology?
ability to quantify occurrence of disease in populations
what is prevalence?
- frequency of disease in a population at a point in time
- only measure of disease occurrence that can be obtained from cross sectional studies
- measures burden of disease in population (which can be compared between populations)
how is prevalence calculated?
# of cases in population / # of people in population
what is incidence?
- # of new cases of a disease within a specified time interval
- probability that an individual will develop the disease during a specific time period
what is the difference between prevalence and incidence?
PREVALENCE = all cases
- dependent on incidence and duration of disease
- individuals only leave "pool" of prevalent cases when they recover/die
INCIDENCE = new cases
how is incidence estimated?
- define the time period under question
- define the denominator = total population at risk
- define a true case by having an accurate test (easier for infections which have a short time period rather than chronic infections)
what happens to prevalence if incidence stays the same?
prevalence can go up if you are keeping people with the disease alive
what is mortality?
the number of deaths from a specific disease in a given time period
how is mortality calculated?
deaths from disease in a given time period / population at start of time period
describe the relationship between mortality, incidence and prevalence
if mortality = incidence the epidemic is stable
if mortality is reduced (people are kept alive for longer):
- incidence may go up as people are more able to transmit diseases to other people
- prevalence may go up as there are more cases and fewer people dying
what is morbidity?
the number of cases of ill health, complications or side effects attributed to a particular condition over a period of time
what is the difference between mortality and morbidity?
MORTALITY = # of people who died
MORBIDITY = state of being diseased/unhealthy
how is morbidity measured?
- scores/predicted morbidity assigned to ill patients with systems such as APACHE II, GCS, PIM2, SOFA
- these help decide the treatment that should be given
- these are useful in comparing 2 sets of patients or different time points in hospital
how is mortality measured?
- rates are normally expressed as # of deaths/1000 individuals/year
which country has the highest death rate and what is it?
swaziland - 30.83 deaths/1000 individuals/year
what are the leading causes of death?
- heart diseases
- cerebro-vascular disease
- respiratory infections
in 3rd world countries 58% of the mortality reported was due to malnutrition
what are the 6 leading causes of infectious disease?
- Lower respiratory infections
- Diarrhoeal diseases
Look How Dey Teach (Muslim Medics)
what does age standardised death rate mean?
age adjustment which allows populations to be compared when the age profiles are quite different
why are age standardised death rates important?
- measuring how many people die each year and why is important in assessing the effectiveness of a country's health system
- can help determine whether health actions are being correctly focused
- almost 15% of deaths from infectious disease are in children <5
- most of these preventable deaths in children occur in LICs and MICs
describe the history of AIDS
- 1st case was David Carr in 1959 who was found to have PCP and CMV infections, never previously reported in adults
- in 1980 a 33 year old man was admitted with PCP
- in 1981 5 gay men had similar illnesses
- GRID = "Gay Related Immune Disease"
- growth of the epidemic in the US from 5 cases in 1980 to 79,000 cases in 1993
- 1.3m living with HIV by 2006
- case control studies conducted and all exposures questioned (sexual, medical, chemicals, pets, drugs etc)
- cases had twice as many sexual partners, and a greater history of syphilis
- no association with "poppers" - drug taken by many gay men
- disease was seen amongst young gay men, related to sexual contact
- disease was also seen in injection drug users and transfusion recipients
- 10 women also had the disease - all had sex with bisexuals/drug users
- test for virus arose in 1984 but there is still no treatment
- antiretroviral therapy (ARTs) became available in mid 90s
describe AIDS now
- global disease
- transmission through bodily fluids
- 90% of disease in developing countries
what are the WHO aims for HIV/AIDS?
- no new infections
- no new babies infected
- no more HIV related deaths globally
what is a case control study?
a retrospective study that starts with an outcome and traces back to investigate exposures, comparing individuals with and without the outcome
how is a case control study designed?
1) identify the cases and the controls
2) look back in time to understand which subjects has specific exposures, comparing the frequency of the exposure in the case group to the control group
what is the aim of a case control study?
to determine whether an exposure is associated with an outcome
what are the advantages of a case control study?
- good for investigating outbreaks of infectious disease
describe the successes of the response to the AIDS epidemic
- broad access to ARTs for HIV in poor countries
- 10-fold growth of access to therapy for HIV/AIDS in Africa from 2002-2007
- declines in HIV prevalence in pregnant women
- knowledge of how to eliminate mother -> baby transmission as mother is given ART before delivery
- increased # of effective HIV prevention methods (e.g. safer injection practices, condoms)
describe the challenges of the response to the AIDS epidemic
- for every 1 person on HIV therapy today, 5 are newly infected
- HIV infection rates have only been decreased to a certain level
- many people choose not to be tested
- preventing the 3,550 HIV infections that were diagnosed in the UK in 2008 would have reduced HIV-related costs by £1.1b
outline the global status of HIV
- only 45% of all HIV infected women have access to treatment to prevent transmission to babies
- less than 40% of people with HIV know their status
- more than 4m people increase in HIV over the past year (10 fold increase over past 5 years)
- 6.7m people need ART but only 2.9m are on ART