Breast Cancer Epidemiology Flashcards
What is the WHO 1946 definition of health?
A state of complete physical, mental and social wellbeing, and not merely the absence of disease and infirmity
What is the BMJ 2007 definition of Health?
Health is a condition of well being free of disease or infirmity and a basic and universal human right
What is Disease?
A deviation in bodily structure or function which places the individual at biological or social disadvantage, now or in the future
What is disease a balance of?
- biological abnormality
- symptoms
- social consequences
this relative balance will differ between diseases
What might the biological, Sx and social aspects of DM look like?
Biological: clear abnormality, detected early for some types
Sx: variable, may be late to develop
Social: variable, may be late effect
What are the considerations when trying identify healthy individuals from those with a disease?
- key part of medical practice
- ideally, disease will be associated with clear Sx and signs
Monogenic - clear distinction between diseased and healthy individuals
Polygenic/complex disease: continuum of impaired function and disease/Sx development. Can be difficult to ID pope with that disease
How is health separated from disease?
- Sx, clinical abnormalities
- statistical basis (more than 2 SDs around mean) of biological parameter
- using a predictive parameter for associated morbidities in the future
- Treatment: level at which condition will benefit from Rx e.g. hypertension
What is the epidemiological timeline of disease?
healthy -> at risk -> morbidity -> mortality
Morbidity -> recovery
(And interaction with health services)
Measuring these stages can give an indication of DISEASE BURDEN
What are the simplest indicators of health status in the population?
- mortality
- morbidity
- health service use
- (risk factors)
How is mortality or death rate recorded?
compulsory registration of deaths since 1874
What info is recorded for death registration?
- fact that death has occurred
- characteristics of deceased
(age, place of birth, place of death, occupation, social class) - cause of death
How is the cause of death assessed in death registration?
- certified by medical practitioner/coroner
- coded in accordance with the International Classification of Diseases (ICD10)
What are the main categories of the death certificate?
- disease or condition directly leading to death
- other disease/condition leading to CoD (x2)
- other significant conditions
- Cause of death
Where is the info on death collated?
NHS Central Register and Office of National Stats
What does info or deaths provide?
- interpret info for DEATH RATE
How is the death rate calculated?
number of deaths / population / year
Where is info on the living population gained from?
Census performed every 10 years
managed by office of national stats
What info does the Census include?
every 10 years, next one in 2021
complete count of population
age and sex distribution
suppl info: Birthplace, ethnic origin and occupation
What kind of info does the ONS keep of the living population?
- total population at time of consensus
- immigration and emigration
- deaths
- births, stillborns, abortions
- year by year estimates
- death rates (annual)
- cancer registration and disease notification: incidence rates
- deaths by a particular cause e.g. breast cancer
Why is crude death rate not the informative for breast cancer?
death varies strongly by age
average means that you’re diluting the effect
What are the 2 approaches that are used to deal with the idea that death rates vary with age?
- AGE-SPECIFIC
= death rates over a narrow age-range - AGE STANDARDISED
= summary of age-specific death rates over wider age range
How it the AGE-SPECIFiC mortality rate calculated?
number of breast cancer deaths in age range / number of women aged in that range (per 1000)
given per year (rate)
What are the classic age divisions used for age-specific mortality rate?
45-54
55-64
65-74
etc
What is the relationship between age-specific mortality and age in breast cancer (women)?
increasing age-specific mortality rates with increasing age
[continuous effect]
What is the importance of age-specific mortality rates?
- death rates vary markedly with age
- provide a much more precise death rate estimate
- can be compared with other populations
- Comparison: especially when different populations have different age structures
What is the age structure of South Africa compared to Sweden?
S. Africa: majority of population is v. young <30yo. Very few make it to 70+
Sweden: much more of an even distribution between all age ranges
less stark of a difference between very young and very old
What is the AGE-STANDARDISED mortality rate?
summary of data rates across a broad range of age-groups, taking population age differences into account
Why is AGE-STANDARDISED mortality rate useful?
comparing death rates in different populations (esp when comparing different age structures and times/places)
What are the 2 types of AGE-STANDARDISED mortality rate?
- direct
- indirect
What are the STRENGTHS of mortality data in the UK?
- very good completeness
- high accuracy, moderate for identifying the cause of death
- relevance of data is variable between conditions (v. good for rapidly fatal, poor for chronic)
- good timeliness, public within 1-2yr
What are the LIMITATIONS of mortality data in the UK?
- only moderate accuracy for cause of death
- relevance is limited for chronic or not immediately fatal conditions (e.g. breast ca)
- doesn’t given good info on incidence and survival from Breast Ca
What measures are used to gauge morbidity in the population?
- incidence rate
- prevalence rate
What is the incidence rate?
onset of new cases
marks transition between health and disease
How is incidence rate calculated?
new cases of disease / population at risk
given per unit time
Which population is used as denominator for calculating the incidence rate?
= mid-year population
this is derived from the census
What is the prevalence rate?
= proportion of population at risk, who have disease at a particular time
can be taken at a point in time or over a time range
How is prevalence rate calculated?
= total cases (old and new) / population at risk
Can give a crude indication of DISEASE BURDEN
What are the 2 types of prevalence rate?
- point prevalence rate
- period prevalence rate
How is point prevalence calculated?
(simplest form of prevalence rate)
= number of persons with disease / average number of people at risk in population
AT A DEFINED MOMENT IN TIME
In what conditions, is point prevalence useful?
measuring stable, chronic diseases
Why is point prevalence less useful in sporadic/episodic conditions?
because it is likely to be an accurate estimate of the disease burden
Unlikely that all affected individuals will be symptomatic at exactly the same time of census
e.g. asthma, migraine
How is period prevalence calculated?
(a proportion)
= number of persons with disease / average number of population at risk
OVER A DEFINED PERIOD OF TIME
week/month/year
In which conditions, is the period prevalence rate more useful?
acute, episodic conditions
e.g. migraine, asthma
What are the relationships between prevalence and incidence?
incident cases -> prevalence
prevalence -> deaths + recovery
What is prevalence rate determined by?
- incidence rate (input)
- death rate (output)
- recovery rate (output)
In a steady state, what is the prevalence rate equal to?
= incidence rate x mean duration of disease
What is the value of province + incidence (morbidity) info?
INCIDENCE INFO
- disease trends
- disease causes
PREVALENCE INFO
- disease trends
- Disease burden
- health service needs
What routine info do we have on morbidity in population?
- info on specific illnesses (disease registration and notification)
provides data on new cases, especially useful for incidence
Morbidity rates and derived from info in census info
Which diseases are registered upon diagnosis?
- cancer
- mental illness/disability
- occupations lung disease (asbestos)
- rare childhood disease (e.g congenital defects)
What is the caveat of following up individuals who have been recorded in disease registrations?
follow-up is VOLUNTARY
may be incomplete
= recall bias
What is cancer registration?
- start in 1923
- voluntary national scheme since 1962
- recording of new cancer cases and deaths
- (1971) cancer registrations linked to NHS central register, allowing cancer incidence cohort studies by “flagging”
- usually linked to population estimates
How has cancer registration data informed our understanding?
provides info on:
- incidence
- prevalence
- cancer survival
What is the value of cancer registration info?
- good (>90%) completeness
- high accuracy often with causative primary tissue)
- helpful relevance for all forms of Ca (incidence and prognosis)
- good timeliness with making info public
What are the main strengths cancer registration?
compared with mortality
- data on incidence
- data on survival
What is infectious disease notification?
legal requirement for both clinician and lab staff
Exists since 1876
Data processed by ONS weekly
What is the value of recording info in infectious diseases?
- poor completeness (50%)
- fairly high accuracy
- good relevance
- good timeliness, lag time to publish is very short
What is the relevance of recording info on infectious disease?
Helpful in identifying epidemics
by look at clusters of disease incidence (by location)
What is the difference between disease REGISTRATION and disease NOTIFICATION?
REGISTRATION
attempt to follow up individuals over time (study disease outcomes)
NOTIFICATION
Often compulsory
What are the similarities of disease registration and disease notification?
Both rely on doctors providing info
About cases
Info provided to a central agency e.g. ONS
How is ‘health service utilisation’ measured?
hospital episode systems (HES) record admissions to all NHD hospitals
does NOT take into account A&E or OPD)
How does health service utilisation factor into disease morbidity?
used as an indirect measure of morbidity
What kind of hospital admissions are recorded by the hospital episode systems (HES) record?
- general admissions
- psychiatric admissions
- maternity admission
shows spells of illness not individual patients
How are the diseases recorded for health service utilisation recorded?
coded according to the International Classification of Diseases (ICD)
Info from census used as denominator (population at risk)
What records are kept for primary care as measures of health service utilisation?
- GP data
(weekly returns, prescriptions, national periodic morbidity surveys) - primary care databases (disease codes and treatment codes)
- social services (sickness absence/benefits)
What are the routine health surveys that are performed?
- Health survey for England (since 1994)
- General household survey (1971-2012)
What is the Health Survey for England?
- representative sample of households
- questionnaire, measurements and blood samples
- prevalence, risk factors, treatment for common diseases
What is the general household survey?
- representative sample of households
- questionnaire survey
- prevalence of chronic illness
- cigarette smoking and EtOH intake
What is the epidemiology of breast cancer in the UK?
MORALITY RATE
56 per 100,000 (per year)
INCIDENCE RATE
250 per 100,000 (per year)
Incidence rates are lower in ethnic minority groups and in socioeconomically derived groups)
In which demographics are breast cancer incidence reduced?
- ethnic minority groups
- lower socioeconomical groups (although mortality rates are increased)
What are the main risk factors for breast cancer?
(increasing) age obesity exposure to oestrogen FHx of breast cancer High EtOH intake
At what age, does the incidence for breast cancer increase?
70 years
increases to 350 per 100,000 per year
What are the protective factors for breast cancer?
breast feeding
being physically active
Which types of ‘oestrogen exposure’ can increase risk of breast cancer?
- early menarche
- late first pregnancy (>30yo) or no pregnancy
- late menopause
- obesity
- oral contraceptive use
- HRT
- other oestrogen use (transition for eg)
