Lifestyle & Disease

Lifestyle & Disease

Not every illness is caught from someone else. Many of the biggest killers build up **inside** us over years. Shaped by how we live. This module: what goes wrong in the heart, what a "risk factor" really means, and how cancer spreads.

A clogging heart

In **coronary heart disease (CHD)**, fatty material builds up inside the **coronary arteries**, narrowing them so less blood, and less **oxygen**: reaches the heart muscle. Doctors have several fixes: **stents** (tubes that hold the artery open), **statins** (drugs that lower blood cholesterol), replacement heart **valves**, and even **artificial hearts**.

Treating the patient

Two patients come through a cardiology clinic. Work through the treatment decisions.

• A coronary artery is narrowed by fatty deposits and blood flow must be restored now. Which treatment physically holds the artery open?
• That same patient also has high blood cholesterol, which is speeding up the fatty build-up. Which treatment tackles the cholesterol itself?
• The second patient has a leaking heart valve, but their coronary arteries are clear. What do they need?
• Years later that patient's heart is failing and no donor heart is available yet. What can keep them alive in the meantime?

What each fix does

Two families of disease

Every disease falls into one of two groups, and the dividing line is whether it can pass from one person to another.

Which kind?

A student writes: "Coronary heart disease is communicable, because it runs in families." What is wrong with that?

• Communicable means spread between people by a pathogen, which CHD is not
• Nothing is wrong, because a disease that runs in families is communicable
• CHD has nothing whatever to do with family history
• CHD is caused by a pathogen, but one that happens not to spread

Say what a risk factor is

A risk factor is anything linked to an _____ probability of a disease. Because a risk factor only _____ with the disease, showing a link is not enough on its own: scientists must also demonstrate a _____ before claiming one causes the other.

How lifestyle plays in

Lifestyle choices raise the risk of non-communicable disease: a poor **diet** and **inactivity** (type-2 diabetes, heart disease), **smoking** (lung disease, cancer) and **alcohol** (liver and brain damage). But be careful with evidence: a risk factor **correlates** with a disease. It raises the probability, but correlation alone doesn't prove it **causes** it. A **causal mechanism** must be shown.

Over-claiming

A news article reports a study linking sugary drinks to type-2 diabetes. Tap the sentence that claims MORE than the evidence supports.

• The study found that
• people who drank more sugary drinks had higher rates of type-2 diabetes
• . The researchers say that
• sugary drinks are therefore a risk factor for the disease
• . The article concludes that
• this proves sugary drinks are the sole cause of every case of type-2 diabetes
• . Other scientists add that
• a causal mechanism would still need to be demonstrated

Read the evidence

That same study also found that the people who drank more sugary drinks exercised less on average. Why does that matter when judging the evidence?

• The lower exercise could be contributing too, so the link to sugary drinks alone is less certain
• It does not matter, because only one risk factor can apply to a disease at a time
• It proves sugary drinks cause the disease, since two factors point the same way
• It makes the study worthless, so no conclusion at all can be drawn

Spot the risk factors

Pick the THREE **lifestyle** risk factors for non-communicable disease.

• Smoking
• A poor diet
• Lack of exercise
• Having a parent who had the disease
• Catching flu from a colleague
• Being taller than average

Cancer

**Cancer** is the result of **uncontrolled** cell growth and division, which forms a **tumour**. AQA wants the two kinds told apart precisely.

The dangerous kind

What makes a **malignant** tumour more dangerous than a benign one?

• Its cells invade other tissues and spread in the blood to form secondary tumours
• A malignant tumour is always the physically larger of the two
• A malignant tumour is only ever found in older patients
• A malignant tumour is always painful, whereas a benign one never is

Write it up

A study reports that people who exercise less have higher rates of type-2 diabetes. Explain what can and cannot be concluded from this, using the terms risk factor, correlation and causal mechanism.

• Say what the study actually shows: a correlation between two things.
• Use the phrase risk factor, and define it as something linked to an increased probability.
• Say clearly what the study does NOT show on its own.
• Name what scientists would still need to demonstrate before claiming one causes the other.
• Mention that other factors, such as diet, may be involved as well.