Cardiovascular Health & Risk

• Risk


  The probability that an event will take place
• Probability


  A measure of the chance or likelihood that an event will take place, calculated mathematically (decimal, fraction or %)
• Non communicable conditions


  Diseases which aren't caused by pathogens and can't be spread from one person to another (e.g heart disease, cancer).

  Risk for these can be increased by lifestyle and heredity factors.
• Perceived risk


  The belief/opinion that making a particular choice has potentially negative consequences (opinion based not fact based).

  Perception of risk is based on many factors but mathematical calculations rarely play a part.
• Actual risk


  The true, fact and evidence based risk of something, mathematically calculated.
• Factors affecting perceived risk

  1. How familiar one is with the activity

  2. How much one enjoys the activity (may ignore actual risk if enjoy a lot e.g obesity)

  3. Whether or not you approve of the activity

  (also personal experiences and media influence)

  
  

  Risk may be overestimated if the risk is:

  1. Involuntary (not under their control)

  2. Not natural

  3. Unfamiliar

  4. Dreaded

  5. Unfair

  6. Very small

  Generally, people overestimate the risk of sudden imposed dangers (if making a choice may have immediate -ive consequences) and underestimate the risk if it has an effect in the long term future e.g. smoking, obesity (due to bad eating habits) etc.
• Risk factors


  Factors which affect the risk of an event happening.
• Multifactorial disease


  A disease which results from the interactions of many different factors- not from one simple cause.
• Epidemiology


  The study of patterns of health and disease, to identify causes of different conditions and patterns of infection.
• Factors contributing to health risks

  1. Heredity

  2. Physical environment

  3. Social environment

  4. Lifestyle and behaviour choices
• Correlation


  - A strong tendency for 2 sets of data/variables to change together (can occur without causation).

  - To determine what the risk factors are for a certain disease, scientists look for correlations between potential risk factors and the occurrence of the disease.
• Causation


  - When a factordirectlycauses a specific effect (one factor is the cause of another)

  - Many data sets need to be studied to prove that a correlation is significant (there's a causation).
• Positive correlation


  A correlation where as one variable increases, the other also increases, or as one decreases so does the other.

  
• Negative correlation


  As one variable increases, the other decreases

  
• Statistically unreliable


  Not a big enough sample size ==> not well representative of the population
• Designing a study


  1. Use a big sample size (evidence based on large amounts of data is more likely to be statistically reliable)

  2. Change 1 variable (independent), and control all others (validity)

  3. Measure the dependent variable as precisely as possible, using the correct equipment.

  4. Repeat reading (reliability)

  5. Wide range of independent variable

  6. Longitudinal study (measure independent variable over a long enough time period)

  7. Could be a metadata analysis (reliability)

  8. Avoid bias (transparency on who funds and scientists involved)

  9. Placebo could be used (placebo group used as a control)
• Longitudinal studies


  Scientific studies which follow the same group of individuals for many years (change in a variable can be tracked over time)
• Metadata analysis (meta-analysis)


  When data from all the available studies in a particular area are analysed ==> gives more reliable evidence than any one of the studies alone
• Valid


  An investigation which is well designed to answer the question being asked (control variables for a valid investigation)
• Precision


  Measurements with only slight variation between them (when there's multiple measurements). Use precise equipment.
• Reliable


  Evidence which can be repeated by several different scientists.
• Biased


  - When someone is unfairly for or against an idea.

  - Therefore it matters who carries out a research, who funds it and where it's published
• Evaluate


  - To assess or judge the quality of a study and the significance of the results.

  - It's based on the validity, precision, reliability, and any possible biases in the study.
• Non modifiable risk factors for atherosclerosis (and therefore CVD)

  Factors that you cannot change:

  1. Genes ==> there may be a genetic tendency (trend) is some families, ethnic groups to develop CVD. These trends include:

  - artery that are easily damaged => atherosclerosis => CVD.

  - tendency to develop hypertension => arterial damage => atherosclerosis => CVD

  - inherit high blood cholesterol levels

  2. Age ==> as you get older, your blood vessels narrow (high bp => CVD) and lose elasticity (artery damage ==> atherosclerosis => CVD)

  3. Gender ==> under age 50, men are more likely to suffer heart disease than women (in women under 50, oestrogen reduces plaque build up, and after 50, due to menopause, oestrogen levels decrease).
• Modifiable risk factors for atherosclerosis (and therefore CVD)


  Factors that you can change:

  1. Diet + Obesity ==> being overweight doesn't directly increase CVD risk, but it depends on:

  - where the fat is stored (abdomen => higher risk)

  - how much exercise

  - levels of saturated and unsaturated fats and cholesterol levels in blood

  Being overweight raises bp (higher mass => more blood needed to be pumped to supply O and nutrients to tissues => heart works harder to pump blood) + may cause type 2 diabetes (this causes damage to artery linings)

  
  

  2. High bp/hypertension can cause atherosclerosis => endothelium damage => atherosclerosis. Can also be used to diagnose atherosclerosis (high bp when lumen's narrower + when artery walls less flexible/elastic i.e can't stretch).

  
  

  3. Smoking ==> substances in tobacco smoke can damage endothelium (=> atherosclerosis) + cause narrow arteries (vasoconstriction => raises bp => atherosclerosis)

  
  

  4. Inactivity ==> regular exercise lowers bp, prevents obesity and diabetes, lowers blood cholesterol levels, balance lipoproteins and reduce stress, which lowers bp (=> lower risk of atherosclerosis + CVD, as it reduces plaque formation and keeps present plaques less likely to break i.e more stable).
• Which type of study is a good option when investigating whether a genetic factor contributes more to developing CVD?

  Identical twin studies (cuz they have identical genes) can be used to see how the different environmental factors affect each twin (rather than genetic factors).
• High blood pressure


  - Blood pressure that's regularly more than 140/90 mmHg ==> increases risk of developing CVDs.

  - Normal bp is 120/80 mmHg (bp at systole / bp at diastole)
• Hypertension


  High bp, regularly measuring over 140/90 mmHg, which increases the risk of developing CVDs
• Preventing atherosclerosis and CVD

  - Eat a balanced diet (with variety of fats + fruits and vegetables)

  - Don't smoke

  - Maintain a healthy weight

  - Avoid high bp and type 2 diabetes

  - Reduce constant stress

  - Exercise regularly
• How can one's diet be adapted to reduce the risk of CVDs?

  - Eating fruits and vegetables reduces CVD risk (contain vitamins and minerals ==> antioxidants)

  - Consuming more vitamin C ==> imp. for collagen and connective tissue formation => these form part of the endothelium in your blood vessels => deficiency of vitamin C may cause endothelium damage and hence plaque formation + scurvy i.e gums bleeding, bruising.

  - Consume less saturated fats (increases cholesterol levels) and high cholesterol foods (cause atherosclerosis ==> increase CVD risk)

  - Consume less salt (increases bp => endothelium damage)
• Antioxidant


  - Molecules that inhibit the oxidation of other molecules which can lead to chain reactions that damage cells.

  - They reduce the number of free radicals that can cause tissue damage ==> prevent damage to endothelium ==> prevent plaque formation (atherosclerosis)

  - There is evidence to suggest that these antioxidants can prevent CVD, however, recent meta studies show that the evidence for antioxidants being good for your heart is inconclusive (doesn't prove anything).
• Testing for vitamin C (Core Practical 2)

  1. DCPIP (blue reagent) used to measure vitamin C concentration.

  2. DCPIP is reduced by vitamin C and loses its blue colour (turns colourless, but the colour of the vitamin C solution doesn't change)

  3. The higher the vitamin C concentration, the quicker DCPIP turns colourless ==> can estimate vitamin C conc. by recording the volume of DCPIP added to smth before it starts to remain blue (all vitamin C used up to reduce DCPIP at this point)

  
  

  (DCPIP may turn pink in very acidic solutions e.g lemon juice)
• How do people become overweight and then obese over time?

  - People eat more than is needed to satisfy the body's metabolic needs (amount of energy body needs to generate via metabolic reactions to stay alive) ==> have a positive energy balance (consume more energy than use) ==> excess food energy stored as fat ==> happens over long time periods ==> overweight then obese.

  - Caused by widely available and cheap energy-rich foods (energy input increased) + lack of exercise (energy output decreased)
• Body mass index (BMI)

  - Measure of obesity

  - A calculation to determine if you are a healthy weight by comparing your weight to your height in a simple formula:

  weight (kg) / (height in m)^2

  - BMI < 18.5 kg m^2 ==> underweight

  - 18.5 < BMI < 25 ==> ideal range

  - BMI > 25 and upto 30 ==> overweight

  - 30 < BMI < 40 ==> obese

  - BMI > 40 ==> morbidly obese
• Limitations to BMI


  - Doesn't take into account body composition (fat and muscle %) ==> overestimate body fat in athletes

  - Underestimate body fat in older people (lost their muscle mass)

  - Doesn't take age or gender into account (young people developing ==> body composition changing, but there are special charts for them)

  - Doesn't take international differences into account when predicting CVD risk (some groups have a higher or lower than avg risk of obesity related diseases).

  
  

  These prevent it from being a good predictor of CVDs on its own.
• Waist-to-hip ratio


  - Best measure of obesity and predicting CVD risk

  - Waist size (cm) / hip size (cm)

  - Waist : hip indicating obesity ==> male = > 0.9, female = > 0.85
• Risks associated with being underweight

  - Muscle wasting (weakening/loss of muscle) ==> loss in strength

  - Heart damage
• Reducing obesity


  - Eating less, exercising more to reduce fat stores ==> reduce w : h ==> reduces CVD risk

  - Taxes on fatty foods

  - Educating children to prevent childhood obesity
• 2 types of cholesterol

  Lipoproteins carrying cholesterol:

  
  

  1. Low density lipoproteins (LDLs): made from saturated fats, cholesterol and protein and bind to cell membranes before entering cells. High LDL levels => cell membranes become saturated => more LDL cholesterol stays in blood (cuz can't bind to cell membrane) => can bind to blood vessels => atherosclerosis

  
  

  2. High density lipoproteins (HDLs): made from unsaturated fats, cholesterol and protein. Carry cholesterol from body tissues to liver to be broken down + help remove cholesterol from fatty plaques on arteries => lower blood cholesterol levels => reduces atherosclerosis risk

  
  

  (lipoprotein: conjugated protein with a lipid prosthetic group ==> transport lipids around body)
• LDL : HDL


  - The higher it is, the higher the CVD risk (high LDL concentrations and low HDL concentrations).

  - Controlled by what you eat + genetics (they determine the way your body metabolises the fats you eat and manages cholesterol levels and balance of lipoproteins in blood)