Risk factors and causesSpec 4.2.2.6
In short
A risk factor is an aspect of a person's lifestyle, or a substance in their body or environment, that is linked to an increased rate of a disease. A correlation does not prove that the risk factor causes the disease; a causal mechanism must explain how. Many diseases, such as coronary heart disease, are caused by several interacting factors.
Risk factors are linked to an increased rate of a disease. They can be:
- aspects of a person's lifestyle
- substances in the person's body or environment.
A causal mechanism has been proven for some risk factors, but not for others. A correlation between a risk factor and a disease does not prove that the risk factor causes the disease. A causal mechanism explains how the risk factor leads to the disease.
Many diseases are caused by the interaction of a number of factors. For example, CHD is affected by diet, smoking and how much exercise a person takes, as well as other factors.
Common mistake:‘Risk factor’ does not mean the disease is certain. It means the disease is more likely. Someone with no risk factors can still get the disease.
Written and checked against the AQA GCSE Combined Science (8464) specification · Updated October 2026
Frequently asked questions
Why do enzymes denature at high temperatures?
At high temperatures the shape of the enzyme's active site changes, so the substrate no longer fits and the reaction cannot be catalysed. The enzyme is denatured, and this cannot be changed back. Below the optimum, the rate rises with temperature because particles move faster and collide more often. Enzymes are not killed, because they are not alive.
How are alveoli adapted for gas exchange?
Millions of alveoli give a very large surface area for diffusion. Their walls are one cell thick, so the diffusion distance is short. A network of capillaries carries oxygen away and brings carbon dioxide, and constant ventilation brings fresh air. Both keep a steep concentration gradient, so oxygen diffuses into the blood and carbon dioxide diffuses out quickly.
Why is the left ventricle thicker than the right?
The left ventricle has a thicker muscular wall than the right because it pumps blood all the way around the body at a higher pressure. The right ventricle only pumps blood to the lungs. Both are part of the double circulatory system, in which blood passes through the heart twice on each complete circuit.
All 5 questions on Animal tissues, organs and organ systems
