Health Issues (AQA GCSE Combined Science: Trilogy): Revision Note

Health & Disease

• Health is the state of physical and mental well-being; lots of factors affect the health of an individual

• Diseases, both communicable and non-communicable, are major causes of ill health; ill-health affects not only the sufferer but their family members and the contribution that individual can make to society

  • Ill health can lead to a poorer quality of life or a reduced lifespan

  • The cost of an individual being ill - individuals who are sick may not be able to work and may require expensive healthcare (with the cost being attributed to the individual or a healthcare provider such as the NHS in the UK)

• Communicable diseases are caused by microorganisms called pathogens which can spread between individuals or individuals and animals

  • eg. chickenpox, a common childhood disease, is caused by a viral pathogen called the varicella-zoster virus, whereas Covid-19 is caused by the SARS-CoV-2 virus

• Non-communicable diseases are not caused by pathogens and their effects on health tend to be longer-lasting; examples are asthma, CHD and most cancers

• Factors including diet, stress and life situations may have a profound effect on both physical and mental health

  • Eating a balanced diet that provides the right amount of energy and nutrients helps maintain good health, whereas a poor diet can lead to deficiencies, obesity, diabetes and poor mental health

  • Constantly being under stress can lead to cardiovascular issues (such as high blood pressure, increasing the risk of CHD) and poor mental health

  • Where a person lives and their income can have a profound impact on health - this affects the standard of healthcare that is accessible to them (and what they can afford), what food they buy, etc.

Interactions & Disease

• Different types of disease may interact in ways that negatively affect the health of the individual

• Defects in the immune system mean that an individual is more likely to suffer from infectious diseases; individuals infected with HIV eventually end up with reduced numbers of lymphocytes circulating the body, which reduces the ability of the immune system to fight opportunistic infections like pneumonia

• Viruses living in cells can be the trigger for cancers; the HPV virus can infect cells of the cervix in women, resulting in cervical cancer developing in some cases, whereas some strains of the hepatitis virus can cause liver cancer

• Immune reactions initially caused by a pathogen can trigger allergies such as skin rashes and asthma - these often develop as a result of an overactive immune response

• Severe physical ill health can lead to depression and other mental illness

Disease Incidence: Representing & Calculating

• Scientists and doctors often record the incidence of disease – the number of new cases seen in a population over a set time period (e.g. number of measles cases per month)

• Data on disease can take place in a variety of forms:

  • Graphical and numerical forms

    • Data can be presented as a table, which can be extracted into an appropriate graph; from there, numerical data can be extracted from the chart

    • Graphs must have clearly labelled axes and appropriate scales

  • Frequency tables, bar charts and histograms

    • Frequency tables present how many cases occur in each category

    • Bar charts are used for discrete data (e.g. cases per month)

    • Histograms are used for continuous data (e.g. ages of infected patients)

  • Correlations on scatter diagrams

    • Scatter diagrams plot two variables (e.g. pollution level vs. number of asthma cases)

    • Positive correlation: both variables increase together

    • Negative correlation: one variable increases as the other decreases.

    • No correlation: no clear pattern.

    • Correlation does not prove causation – the link between variables may be due to another factor

Sampling

• When investigating the spread of disease, it is often impractical to collect data from every individual in a population. Scientists, therefore, take a sample, e.g.:

  • Random sampling – each individual has an equal chance of selection, reducing bias

  • Systematic sampling – individuals are chosen at regular intervals (e.g. every 10th person)

  • Stratified sampling – the population is divided into groups (e.g. age groups) and sampled proportionally

  Importance of sampling:

  • Sampling saves time and resources while still allowing meaningful data collection

  • Large, well-chosen samples produce more reliable and representative results

  Application in epidemiology:

  • Sampling enables scientists to identify patterns of disease spread, risk factors, and vulnerable groups

  • Findings are used to guide public health strategies, such as vaccination campaigns or screening programmes