Investigating the Cause of CVDs

Cardiovascular Health and Risk

What is the main purpose of epidemiological studies investigating CVDs?

To identify factors that affect the risk of developing cardiovascular diseases.

Why are most epidemiological studies based on very large sample sizes?

Larger samples are more likely to reveal meaningful patterns and provide statistically significant evidence.

Why is it difficult to control variables in epidemiological studies involving humans?

People differ in many ways, including their genetics, lifestyle and environment, so it is almost impossible to keep all variables except one the same.

What is a sample?

A group of individuals selected from a population to take part in a study.

Why should a sample be representative of the population?

So that conclusions from the sample can reasonably be applied to the wider population.

Why is sample selection important in an epidemiological study?

Poor sample selection can introduce bias and make the results unrepresentative of the wider population.

Why are larger sample sizes generally better than smaller sample sizes?

They make patterns easier to identify, reduce the influence of individual variation and are more likely to produce statistically significant evidence.

What is statistical significance?

Evidence that an observed result or relationship is unlikely to have occurred simply by chance.

What is a longitudinal study?

A scientific study that follows the same group of individuals over many years.

Why are longitudinal studies useful for investigating CVD risk factors?

They allow scientists to observe how lifestyle and other factors affect health over a long period of time.

What is an advantage of following the same individuals in a longitudinal study?

Changes in their lifestyle and health can be tracked over time.

What is a disadvantage of longitudinal studies?

They can take many years to complete and may be expensive and difficult to maintain.

Why can a longitudinal study involving people from only one particular population be limited?

The participants may not represent other populations, so the findings may not be widely applicable.

How can scientists improve the relevance of a longitudinal study?

They can collect data from a large, diverse and representative population.

What is metadata analysis (meta-analysis)?

Analysis of data from all available studies in a particular area.

Why is meta-analysis useful?

It combines evidence from several studies and can provide more reliable evidence than a single study alone.

Why can meta-analysis be more reliable than an individual study?

It uses a much larger overall amount of evidence, reducing the influence of unusual results from individual studies.

What should scientists examine when evaluating a scientific study?

Its validity, precision, reliability, methodology, sample selection, possible bias, funding and publication.

What does valid mean in a scientific investigation?

The investigation is well designed to answer the question being asked.

How can scientists determine whether a study is valid?

They examine whether the methodology is appropriate and whether the investigation actually measures what it is intended to measure.

What does precise mean?

Measurements have very little variation between them.

What does reliable mean?

The investigation can be repeated by other scientists who obtain similar results.

How can the reliability of scientific evidence be increased?

Other scientists can repeat the investigation and check whether similar results are obtained.

Why is repeatability important in scientific research?

Similar results from repeated studies increase confidence that the original findings are reliable.

What is bias?

When someone is unfairly for or against an idea, which may influence the design, interpretation or reporting of a study.

How can funding potentially introduce bias into a study?

A person or organisation funding the research may have a vested interest in obtaining a particular result.

Why should you know who carried out and funded a scientific study?

It helps identify possible conflicts of interest or sources of bias.

Why is it useful to know where a scientific study was published?

It helps you assess the quality and credibility of the evidence.

What does it mean to evaluate a scientific study?

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

What should you do when evaluating the conclusions of a study?

Consider the conclusions in light of the methodology, validity, reliability, precision and possible sources of bias.

What is a risk factor for CVD?

A factor that increases or decreases the probability of developing cardiovascular disease.

Do risk factors necessarily cause cardiovascular disease?

No. They contribute to the probability of developing the disease but do not mean the disease will definitely occur.

What are the two main groups of risk factors for CVDs?

Non-modifiable risk factors and modifiable risk factors.

What is a non-modifiable risk factor?

A risk factor that an individual cannot change.

What is a modifiable risk factor?

A risk factor that can potentially be changed, usually through lifestyle or behaviour.

What are the three main non-modifiable risk factors for atherosclerosis and CVD?

Genes, age and gender.

How can genes affect the risk of CVD?

Some people inherit genetic tendencies that make them more likely to develop conditions associated with CVD.

What evidence suggests there is a genetic component to CVD?

Studies show tendencies to develop CVD within some families and ethnic groups, and identical-twin studies show greater similarity than non-identical twins.

What inherited characteristics can increase the risk of CVD?

A tendency to have easily damaged arteries, develop hypertension or have problems regulating cholesterol balance.

How can inherited susceptibility to arterial damage increase CVD risk?

Arteries that are easily damaged are more likely to develop atherosclerosis.

How can a genetic tendency to hypertension increase CVD risk?

High blood pressure can damage arterial walls, increasing the likelihood of atherosclerosis and other cardiovascular diseases.

How can inherited problems with cholesterol balance increase CVD risk?

Abnormal cholesterol levels can contribute to fatty deposits and plaque formation in arteries.

Why does age increase the risk of CVD?

As people get older, blood vessels begin to lose elasticity and narrow slightly, increasing the likelihood of cardiovascular disease.

What happens to blood vessels as people age?

They gradually lose elasticity and tend to become narrower.

Why can reduced elasticity of arteries increase cardiovascular risk?

Less elastic arteries are less able to accommodate pressure changes and are more susceptible to problems associated with cardiovascular disease.

How does gender affect CVD risk?

Statistically, men under about 50 are more likely to develop heart disease and other CVDs than women of the same age.

Why do pre-menopausal women generally have a lower risk of CVD than men of the same age?

The hormone oestrogen appears to reduce the build-up of atherosclerotic plaque.

How does oestrogen affect CVD risk?

Oestrogen appears to reduce plaque build-up, giving pre-menopausal women some protection against CVD.

What happens to women's CVD risk after menopause?

Oestrogen levels fall, reducing its protective effect and increasing the risk of cardiovascular disease.

Why is gender considered a non-modifiable risk factor?

A person's biological sex-related risk cannot be changed through lifestyle choices.

Why is age considered a non-modifiable risk factor?

Age cannot be changed by lifestyle or medical intervention.

Why are genes considered non-modifiable risk factors?

The genes a person inherits cannot normally be changed.

Why are identical twin studies useful for investigating genetic risk factors?

Identical twins have the same genes, so similarities in disease occurrence can provide evidence for a genetic influence.

Why can differences between identical twins help scientists investigate environmental effects?

Because identical twins have the same genes, differences between them may be caused by environmental or lifestyle factors.

What are fraternal twins?

Twins that develop from different eggs and are genetically similar to ordinary siblings rather than genetically identical.

What is the difference between identical and fraternal twins in genetic studies?

Identical twins share essentially all their genes, whereas fraternal twins share only about half of their variable genetic material on average.

What would scientists expect if a disease has a strong genetic component?

Identical twins should show greater similarity in disease occurrence than fraternal twins.

What did the Swedish twin study investigate?

It investigated the relationship between genetics, age and heart disease using thousands of pairs of male twins.

What did the Swedish twin study find about younger identical twins?

If one identical twin died of heart disease between ages 36 and 55, the other twin's risk of also dying from heart disease was much higher than if neither was affected.

What did the twin study suggest about heart disease in younger men?

There appears to be a clear genetic influence on heart disease in younger men.

How did the apparent genetic influence on heart disease change with age in the twin study?

The correlation between twins decreased as they became older.

What does the declining twin correlation with age suggest?

Environmental and lifestyle factors may become increasingly important in determining heart disease risk as people age.

What is heritability?

The tendency of a characteristic or disease susceptibility to be inherited.

Does high heritability mean that a disease is caused entirely by genes?

No. Environmental and lifestyle factors can still influence whether the disease develops.

Why might estimates of heritability change depending on follow-up time?

The relative contribution of genetic and environmental factors may appear different as participants age and accumulate different lifestyle exposures.

What is follow-up time in an epidemiological study?

The period after the original study during which participants continue to be monitored or their outcomes are reassessed.

Why are twin studies not perfect evidence that genes cause CVD?

Identical twins may also share similar environments and lifestyles, so environmental factors can contribute to the observed similarities.

Why should epidemiological results be interpreted cautiously?

Associations between factors do not automatically prove causation, and results may be affected by confounding variables or bias.

What is a confounding variable?

A factor other than the variable being investigated that may influence the outcome.

Why are confounding variables a problem in CVD studies?

They can make it appear that one factor is responsible for a change in CVD risk when another factor is partly or wholly responsible.

How can scientists strengthen evidence for a CVD risk factor?

By using large representative samples, long-term studies, repeated investigations and evidence from multiple independent studies.

Why is evidence from several independent studies stronger than evidence from one study?

Similar findings from different studies reduce the likelihood that the result is due to chance, bias or problems with one study's methodology.

What should an ideal epidemiological study try to do with variables?

Investigate one factor while keeping other variables as controlled as possible.

Why is this ideal difficult to achieve in humans?

Human populations vary greatly in genetics, lifestyle, diet, environment and many other factors.

What is the relationship between sample size and reliability of conclusions?

Large samples generally provide stronger evidence because individual differences have less influence on the overall pattern.

Why can a small sample produce misleading conclusions?

Chance variation or unusual individuals can have a disproportionately large effect on the results.

What makes a sample representative?

It reflects important characteristics of the wider population being investigated.

How could an unrepresentative sample affect conclusions?

The results may not apply accurately to the population as a whole.

Why is long-term evidence particularly useful for cardiovascular disease?

CVD often develops gradually over many years, so long-term exposure to risk factors needs to be considered.

What is the difference between validity and reliability?

Validity concerns whether a study properly answers the intended question, whereas reliability concerns whether similar results can be obtained when the study is repeated.

What is the difference between precision and accuracy?

Precision describes how close repeated measurements are to each other, whereas accuracy describes how close a measurement is to the true value.

Can measurements be precise without being accurate?

Yes. Measurements can be very similar to each other but consistently different from the true value.

What is a vested interest?

A personal, financial or organisational interest in obtaining a particular outcome.

How could a vested interest affect scientific research?

It could introduce bias into how a study is designed, analysed, interpreted or reported.

Why should scientific studies clearly describe their methodology?

It allows other scientists to evaluate the study and attempt to repeat it.

Why is peer scrutiny important in science?

It allows other scientists to identify weaknesses, evaluate evidence and test whether conclusions are justified.

Define longitudinal study.

A scientific study that follows the same group of individuals for many years.

Define meta-analysis.

Analysis in which data from all available studies in a particular area are analysed together.

Define valid.

Describes an investigation that is well designed to answer the question being asked.

Define precision.

Measurements with only slight variation between them.

Define reliable.

Describes evidence that can be repeated by different scientists who obtain similar results.

Define biased.

Being unfairly for or against an idea in a way that may influence the outcome or interpretation of research.

Define evaluate.

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

Define heritability.

The tendency of a characteristic or susceptibility to disease to be inherited.

Explain why a large sample size is important when investigating CVD risk factors.

Humans vary greatly, so a large sample reduces the influence of individual variation, makes patterns easier to detect and increases confidence in the results.

Explain why identical twin studies can provide evidence for a genetic component to CVD.

Identical twins have the same genes. If they show greater similarity in CVD occurrence than fraternal twins, this supports the idea that genetic factors influence CVD risk.

Explain why twin studies cannot prove that CVD is entirely genetic.

Twins may share environmental and lifestyle factors, and CVD is multifactorial, so both genetic and environmental factors contribute to risk.

Explain how ageing can increase the risk of CVD.

With age, blood vessels lose elasticity and may narrow, increasing susceptibility to atherosclerosis and cardiovascular disease.

Explain why men under about 50 generally have a higher CVD risk than women.

Oestrogen in pre-menopausal women appears to reduce plaque build-up, providing some protection against CVD until oestrogen levels fall during menopause.

Explain the difference between modifiable and non-modifiable CVD risk factors.

Modifiable risk factors can potentially be changed through behaviour or lifestyle, whereas non-modifiable risk factors such as genes, age and gender cannot be changed.