By the end of this lesson
- Identify major CHD risk factors.
- Explain mechanisms connecting factors to disease.
- Distinguish risk from certainty.
BIG QUESTION
Why do heart attacks rarely have one single cause?
Vessel damage, plaque development, clotting and cardiac demand interact with behaviour, environment and inheritance.
Atherosclerosis narrows coronary arteries
Damage and inflammation in arterial walls can lead to lipid-rich atheromaA fatty, inflammatory deposit that builds up in the wall of an artery, narrowing it and reducing blood flow. and fibrous plaques. The lumen narrows and the wall becomes less elastic.
Plaque rupture can trigger a thrombus, abruptly reducing oxygen delivery to heart muscle.
Several factors are modifiable
Smoking, physical inactivity, diets high in saturated fat/energy, obesity, high blood pressure and poorly controlled diabetes can increase risk through overlapping mechanisms.
Changing a factor lowers probability; it does not guarantee prevention.
Some factors cannot be changed
Age, biological sex patterns and inherited variants/family history can alter baseline risk. They may interact with modifiable exposures.
Risk-factor evidence is population-based. Avoid blaming individuals or assuming correlation alone proves a mechanism.
CHD risk factors
A high-quality answer names both factor and plausible pathway.
| Factor | Modifiable? | Possible link |
|---|---|---|
| Smoking | Yes. | Endothelial damage, clotting, reduced oxygen carriage. |
| High blood pressure | Often partly. | Arterial wall damage and cardiac workload. |
| High saturated-fat/energy diet | Yes. | Can raise LDL and promote obesity/plaque risk. |
| Physical inactivity | Yes. | Affects body mass, lipids, pressure and glucose control. |
| Diabetes | Manageable. | High glucose damages vessels. |
| Age/family history | No. | Accumulated exposure/inherited susceptibility. |
Language that earns precision
- coronary heart disease
- Reduced blood supply to heart muscle due to disease of coronary arteries.
- atheroma
- Fatty-inflammatory deposit within an arterial wall.
- risk factor
- Characteristic associated with increased probability of disease.
- thrombosis
- Formation of a clot within a blood vessel.
Common misconceptions
Claim: One fatty meal blocks a coronary artery.
Correction: Atherosclerosis develops over time through multiple interacting processes.
Claim: Everyone with a risk factor develops CHD.
Correction: Risk changes probability, not certainty.
Claim: Only cholesterol matters.
Correction: Smoking, pressure, diabetes, inactivity, genetics and other factors contribute.
Match the answer to the command word
Factor → vessel/oxygen mechanism → reduced coronary supply.
Separate association from causation and note confounding.
Recall, apply, then justify
Explain how smoking increases CHD risk.
Hint
Use vessel damage, clotting or oxygen carriage.
Suggested marking points
- Smoke damages artery lining/promotes inflammation.
- Atheroma/plaque or clot risk increases.
- Carbon monoxide reduces oxygen carriage.
- Coronary supply may fail to meet myocardial demand.
Explain why family history is a risk factor but not a diagnosis.
Hint
Probability and interaction.
Suggested marking points
- Inherited variants/shared exposures can raise probability.
- An individual may not develop CHD, especially as many other factors interact.
Evaluate a claim that an association between inactivity and CHD proves inactivity is the only cause.
Planning hint
Use mechanisms and confounders.
What a strong design includes
- Association alone does not prove a single cause.
- Diet, smoking, deprivation, age or illness can confound the relationship.
- Reverse causation is possible if illness reduces activity.
- Plausible mechanisms support a contribution from inactivity.
- Dose-response and intervention evidence strengthen inference.
- CHD is multifactorial, so “only cause” is unjustified.