14 Non-communicable diseases Flashcards
what is the definition of a non-communicable disease?
a disease which is non-infectious and non-transmissable among people
what are the four main types of non-communicable diseases?
cardiovascular
cancer
chronic respiratory diseases
diabetes
what is the definition of a risk factor?
a variable associated with an increased chance of developing a disease or infection
what are the three ways in which a risk factor can be expressed?
relative risk
fraction of incidences occurring in a group having been exposed to the risk factor
increase in incidence in the exposed group
how is the risk calculated?
number of people experiencing event / number of people exposed to risk factor
OR
A = p x (1 + r)^n
where: A = number of global cases p = initial number of cases r = annual increase n = number of years
what are the three main risk factors associated with developing non-communicable diseases?
preexisting conditions
behaviour/lifestyle choices
hereditary/genetic factors
give three of the Bradford-Hill criteria for establishing causal relationships
strength
temporality
consistency
theoretical plausibility
coherence
specificity
experimental evidence
what are the
- preexisting conditions
- behavioural/lifestyle choices
- hereditary/genetic factors
associated with strokes?
conditions:
- hypertension
- high cholesterol
behaviour:
- excessive salt
- excess alcohol inactivity
hereditary
- sickle cell disease
what are the
- preexisting conditions
- behavioural/lifestyle choices
- hereditary/genetic factors
associated with lung cancer?
conditions:
- chronic lung diseases
- radiation exposure
behaviour:
- smoking
- asbestos exposure
hereditary:
- 1st degree family member with lung cancer
- gender
what are the
- preexisting conditions
- behavioural/lifestyle choices
- hereditary/genetic factors
associated with asthma?
conditions:
- another allergic condition
behaviour:
- exposure to allergens
- smoking
hereditary:
- blood relative with asthma
what are the
- preexisting conditions
- behavioural/lifestyle choices
- hereditary/genetic factors
associated with type 2 diabetes?
conditions:
- aged 45+
- gestational diabetes
behaviour:
- physical activity < 3 times a week
- being overweight
hereditary:
- blood relative with diabetes
- certain ethnicities
what is the definition of a tumour?
a lump or growth of abnormal cells that divide uncontrollably
what is the definition of cancer?
a disease usually caused by a mutation that causes uncontrolled cell division and the subsequent formation of a tumour
what are the four types of cancer?
carcinomas (internal and external body surfaces)
sarcomas (supporting structures)
lymphomas (lymph nodes and immune system)
leukemias (immature blood cells)
what is metastasis?
the process in which cancer cells break from the primary tumour and spread to initiate a secondary tumour formation at a different location
what is the difference between a benign and malignant tumour?
benign:
- slow growing
- not normally life-threatening
- do not normally grow back
malignant:
- fast growing
- metastatic
- can be life-threatening
what is the function of proto-oncogenes?
to stimulate cell division after stimulation from a growth factor
how can mutated proto-oncogenes cause cancer?
the base sequence mutates –> oncogenes with different receptor proteins
∴ DNA replication is triggered without the extra-cellular growth factor
what is the function of tumour suppressor genes?
to code for proteins that prevent cell division
and initiate breakdown of damaged cells in apoptosis
how can mutated tumour suppressor genes cause cancer?
apoptotic stimulation is lost ∴ damaged DNA can be replicated
what is a mutagen?
a physical, biological or chemical agent that mutated the DNA of an organism and increases the frequency of mutations above the natural background level
give an example of a
- physical
- biological
- chemical
mutagen
physical: ionising radiation
- high energy breaks H bonds in DNA –> change in DNA base sequence
- DNA most susceptible at end of interphase and during mitosis
biological: viruses
- can interfere with p53 production –> prevention of apoptosis
chemical: benzene
- react with and alter structure of DNA
- can be counteracted with anti-oxidant
outline the role of the Ras gene and explain [how its mutated form can cause cancer]
division stimulated by extra-cellular messengers
[division stimulated by Ras gene without hormone ∴ cell cycle inhibition removed]
outline the role of the c-Myc gene and explain [how its mutated form can cause cancer]
regulator gene on chromosome 8 responsible for regulating 15% of gene expression
[Myc constantly expressed –> unregulated expression of genes –> cell proliferation and cancer formation]
outline the role of p53
a transcription factor which plays a role in apoptosis, genomic stability and inhibition of uncontrolled cell division
temporarily stops cell cyle at G1/S checkpoint to allow reparation of damaged DNA
outline the use of x-rays in detecting cancer
give one strength and one weakness of this method
high energy radiation and photographic film plate create a black and white image, depending on the absorbency of the tissues
+ quick; non-invasive
- can’t distinguish without further tests
outline the use of mammograms in detecting cancer
give one strength and one weakness of this method
low energy x-rays of the breast
+ quick; non-invasive
- can’t distinguish without further tests
outline the use of computerised axial tomography (CAT) scans in detecting cancer
give one strength and one weakness of this method
x-ray tube rotates around patient and sends x-rays through their body to a photographic plate which captures a black and white image
+ non-invasive; produces a 3D image
- uses x-rays; can’t distinguish without further tests
outline the use of ultrasound in detecting cancer
give one strength and one weakness of this method
high frequency sound waves are picked up by a handheld transducer and converted to an image by a computer
+ non-invasive; no x-rays
- can’t distinguish without further tests
outline the use of magnetic resonance imagery (MRI) scans in detecting cancer
give one strength and one weakness of this method
creates a magnetic field, which causes protons in H atoms to line up; radio waves then ‘spin’ the protons - the resulting signal is converted into a 3D image
+ non-invasive; good for soft tissues
- costly; can’t distinguish without further tests
outline the use of positron emission tomography (PET scans) in detecting cancer
give one strength and one weakness of this method
a radioactive tracer (e.g. fluorodeoxyglucose) is injected and used as a marker for glucose uptake; scanner detects gamma radiation given off by the tracer to produce coloured images
+ accurate; fine detail; 3D coloured images
- can’t distinguish without further tests
outline the use of biopsies in detecting cancer
give one strength and one weakness of this method
cell/tissue sample is removed from the body and analysed in a lab for definitive diagnosis
+ can distinguish
- invasive
outline the use of blood tests in detecting cancer
give one strength and one weakness of this method
diagnosis given concentration of certain compounds in the blood; indication of response to treatment
+ effective diagnostic tool
- invasive
what is screening?
testing people who are known to be at risk of a certain condition before symptoms develop
what four cancers are routinely screened for in England?
breast
bowel
cervical
prostate
who is offered screening?
healthy individuals who have an elevated risk
why might a false negative be diagnosed?
cancer doesn’t show up on x-ray
cancer cannot always be detected immediately
cancer can develop rapidly between scans
why might a false positive be diagnosed?
after lots of mammograms, the chances of a false positive increases
human error (corrected by follow up tests)
what are the disadvantages of screening?
distress from false positives
unnecessary treatment of benign tumour
most are false negatives - targeted screening would be more cost effective
what are the two genes most commonly associated with breast cancer?
BRCA1 (c.17)
BRCA2 (c.13)
name two other genes associated with and describe their effect in causing breast cancer
TP53 + PTEN
produce tumour-supressor proteins ∴ mutations in these genes –> DNA damage not properly repaired
what is the risk of developing breast cancer?
1 in 8 women (increases with age)
~ 1% risk for BRCA1 male carriers aged 70+
why and how do we test for breast cancer?
only if strong family risk
required a living relative with breast cancer
mutation search (takes weeks/months)
i.e. predictive testing
what condition makes bowel cancer more likely? what percentage of cases is it associated with?
hereditary non-polyposis colorectal cancer (HNCC)
2-5%
what other organs can HNCC increase the chances of cancer in?
uterus
urinary system
gastrointestinal tract
what are the two ways of treating breast cancer by surgery?
lumpectomy - removing the tumour and barrier tissue
mastectomy - removing the whole breast and lymph nodes
how can colon cancer be treated by surgery?
colectomy - tumorous section removed and colon rejoined by anastomosis
what is chemotherapy? what are some potential side effects?
the use of chemicals that are toxic to dividing/cancerous cells
- loss of appetite
- nausea
- increased risk of infection
- fatigue (due to low RBC count)
what is radiotherapy?
ionising radiation is accurately targeted to destroy actively growing cells
what is immunotherapy?
monoclonal antibodies can be tagged with an enzyme that converts an inactive form of a cytotoxic drug into an active form that targets cancerous cells
what is hormone therapy in relation to cancer treatment?
oestrogen - stimulates transcription of genetic material if cells have ER+ receptors
aromatase inhibitors - can be given to post-menopausal, early-stage breast cancer sufferers
LH blockers - prevent oestrogen synthesis
