Causes of Disease

Microorganisms - are single celled organisms including bacteria, viruses and fungi. Some are beneficial and some are pathogens.

Disease - is a change in the body or mind with adverse effects on health. Has physical, mental and social aspects.

Infection - when a disease leads to symptoms.

• For a microorganism to be a pathogen it must:
  • Gain entry.
  • Colonise tissues.
  • Resist defences.
  • Damage tissues.
• They gain entry by:
  • Penetrating an interface with the environment e.g cut, gas exchange system (thin, moist) or digestive system (food carries them in).
• They cause disease by damaging host tissue or producing toxins.

Correlation - occurs when a change in 1 or 2 variables is reflected by a change in another variable, i.e. the realtionship between 2 variables.

Causal link - change in 1 variable results from or is caused by a change in another.

Looking Critically at Data

• Right factor measured.
• Correct questions asked and any unanswered.
• How data was gathered, with reliable method and right apparatus.
• If researcher had vested interets.
• Repeated by others.
• Sample size and age of data.
• Any other factors to explain causal link.

Lifestyle - way of life including patterns of behaviour and personal choices affecting health risk.

Risk - a measure of probability damage to health will occur as a result of a given hazard. It has 2 elements: probability that the hazardous event will occur and consequences of that event.

• Health risks need a timescale.
• Statistics can be misleading.
• Risk is often relative - risk measured by comparing likelihood of harm occurring in those exposed to a hazard compared to those who aren't.
• Risk factors and cancer:
• Carcinogenic factors risk contracting cancer e.g. smoking, diet, obesity, exercise and sunlight.
• Risk factors and CHD:
• Some factors beyond control e.g. genes and age.
• Lifestyle factors e.g. smoking, high blood pressure, cholesterol, BMI higher than 25, salt and fatty acids in diet and lack of exercise.
• Reduce risk by having less alcohol and more antioxidants.