PPS Flashcards
3 Models of Stress
- Stress as a response: General Adaptation Syndrome.
- Stress as a stimulus: Life Change Model
- Stress as a process: Transactional Model
Definition of stress
A physical and emotional response to any situation that may be perceived as threatening or exceeding the person’s ability to cope with it
Key factors associated with increased stress
o Unpredictable (sudden bereavement, made redundant)
o Uncontrollable (noisy neighbours)
o Imminent (driving test today)
o Occurring at unexpected time (being widowed in 30s)
o High amounts of life change (kids)
Stages of GAS model of stress
- Alarm reaction (immediate reaction)
- Resistance (attempts to reverse effects of alarm stage)
- Exhaustion (body’s defences/resources are depleted and ability to resist stressor declines)
Strengths of GAS
Laid foundations to future stress-physiology research
Highlighted core biological response
1st to outline stress-illness link.
Limitations of GAS
Assumes automatic response to external stressor
All stressors don’t produce same uniform response
Individual variability (no consideration for influence of individual psychosocial factors)
In the Life Change Model, stress is seen as:
the amount of adjustment/ number of life changes a person is faced with in a certain timeframe e.g. moving house, new job
Limitations to Life Change Model of Stress
• People react differently to similar events – is divorce always stressful/can it be relief?
• Recall - Evidence based on retrospective assessment-> people who are ill are more likely to look for cause and attribute it to past events.
• Severity e.g. death- sudden or expected?
• Restricted range of events- disasters omitted, non-events e.g. not becoming pregnant, not getting into university.
• Ignores relationship between stressors e.g. major ones can trigger minor ones and vv : difficult to establish causality.
• Moderating variables e.g. social support not considered
Strength/ evidence of Life Change Model
Evidence:
• Stressful life events are associated with changes in immune response .
• Chronic illness: MS pts- the greater the number of acute life stressors the more likely the relapse.
• Life event stress was associated with more depressive symptoms and worse QoL in individuals w COPD.
Bereavement studies:
• Death of a child aged 10-17 years = 31% inc. in mother’s risk of all-cause mortality.
• Inc. risk of mortality following death of a parent, sibling and spouse (Unexpected bereavement associated with greater risk than bereavement following chronic illness)
• Anniversary reactions: Increased mortality risk among mothers who lost a child aged 1 – 17yrs during anniversary of week of death (CVD and suicide most common causes).
According to Lazarus and Folkman stress is
a process/ series of transactions
Limitations of Transactional model of Stress (Lazarus and Folkman)
- Lack of empirical evidence (difficult to test)
- Primary and Secondary appraisal may be linked
- Emotions may influence appraisal
- Assumes that demand outweighing resources is all that is needed for stress (doesn’t account for value/ stakes , motivational relevance of stressor can play a role)
- Variability and complexity of individual stress response
Strengths of Lazarus and Folkman Model of stress (Transactional Model)
- Highly influencial
- Most applicable as a model
Definition of coping
Attempt to manage perceived demands that cause stress.
What are the two coping strategies
Problem-focused: Seeks to reduce demands/ increase resources.
Emotion-focused: Seeks to manage emotional response to stressor.
Mediators of stress
- Personality (Type A personality, Neuroticism/ -ve effect, perfectionism)
- Social support (Instrumental, Informational, Emotional)
Definition of screening
Systematic, pop-based method to determine if apparently healthy people are at higher risk of a health condition, so early treatment/info provided, to help them make informed decisions.
Examples of screening programmes in NHS
- Newborn hearing screening programme (NHSP)
- Diabetic eye screening (DES) programme
- Breast screening programme (BSP)
- Cervical screening programme (CSP)
- Fetal anomaly screening programme (FASP)
- Newborn blot spot (NBS)
Advantages of screening
Early detection of condition - can reduce risk of developing or dying from the disease – provide more options for treatment
Tests are typically quick to perform and cheap
Disadvantages of screening
Not 100% accurate:
False ID as high risk – unnecessary anxiety, further tests
False ID of low risk – provide false reassurance
Differentiate between sensitivity and specificity
Sensitivity = the ability of a test to correctly ID those with disease
No. of true positives/ no of true positive+ false negatives
Specifity = the ability of a test to correctly classify an individual as disease-free
No of true negatives/ no of true negatives+ false positives
What is Positive predictive value (PPV)?
The probability that following a positive test an individual will actually have the disease
True positive/ true positive + false positive
What is the Negative Predictive Value (NPV)?
The probability that following a negative test the individual will not truly have the disease
True negative/ true negative + false negative
Describe UK policy for screening for Breast cancer
Rationale
Save lives- finding at early stage when too small to see/feel. Screening doesn’t prevent the person from developing breast cancer.
Risks
Some diagnosed & treated that would never otherwise have been found or caused them harm. X-rays from a mammogram can very rarely cause cancer but having one every 3 years for 20 years slightly increases risk. Mammograms do not find all cancers/ can be missed on interpretation.
Criteria
- Inclusion age – all women aged 50 years old up to their 71st birthday invited for breast screening every 3 years. 1st invitations sent between the woman’s 50th and 53rd birthdays.
- Women aged 71 years or older – still at risk. No longer receive screening invitations but can still have breast screening every 3 years.
- Contact - Some local breast screening services may send SMS appointment reminders.
Screening process:
- During screening, 4 mammograms done– 2 for each breast. Performed by a specialist mammographer (female). Appointment ~30 minutes, mammograms only take a few mins.
- 2 views – craniocaudal and mediolateral oblique. Reduces overlapping anatomy, decreases tissue thickness, less scatter/blurring of anatomical structures, less motion and lower radiation dose.
- Results delivery- sent by post within 2 weeks of appointment. Results also sent to GP.
Results: no sign of breast cancer = No further tests required & invited again for screening in 3 years.
Results: further tests needed - triple assessment (1. Breast exam, Hx taken. 2. Imaging – US or additional mammograms. 3. Needle biopsy
Factors Increasing Risk of VTE
• Reduced rate of blood flow
• Increased coagulability of blood
• Damage to venous endothelium (e.g. by trauma/severe injury to lower limbs and pelvis)
What is Virchow’s Triad?
Describes stasis/ reduced rate of blood flow, increased coagulability of blood, and venous endothelial injury as three important factors that contribute to the initial thrombosis.
Consider strategies for prevention of air travel related DVTs
Individual actions:
High Risk individuals
- Avoidance of flights (especially long-haul)
- Elastic compression stockings
- Pharmacological e.g. LMWH – assess possible safety concerns
Low-risk individuals/ Entire population
Lower limb movement (exercise calf muscles while seated, walk about regularly. keep well hydrated, avoid alcohol & coffee)
Societal actions:
Design of airplanes/filling of airplanes
- Seating: Seat density, difficulty leaving seats, narrow or obstructed aisles, trolleys, film screens, (“Economy-class syndrome”);
- Special seats with legroom/aisle access
- Oxygen levels to avoid hypoxia.
Differentiate between precision and accuracy
• Accuracy: how close a measured value is to the actual value.
• Precision: how close a series of measurements are to 1 another/ how reproducible the numbers are.
Main Sources of Bias in Case-Control Studies
Information bias
Selection bias
What is selection bias
Systematic error due to difference in study groups in measured and unmeasured characteristics, leading to differential prognosis of outcome
What is information bias?
In which info on exposure obtained from the cases and controls is not comparable (e.g. recall bias – where cases are more motivated to recall exposure than controls)
