Non-communicable diseases cannot be caught from another person; instead they develop over time due to lifestyle choices, genetic factors, or environmental exposures. Cardiovascular disease, type 2 diabetes, and many cancers fall into this category and account for the majority of deaths worldwide.
What is a non-communicable disease?
A non-communicable disease (NCD) is one that cannot be passed from person to person. It is not caused by a pathogen. Instead, NCDs develop gradually, often over decades, due to a combination of genetic predisposition, lifestyle behaviours, and environmental factors.
Contrast this with communicable diseases such as influenza or tuberculosis, which are caused by pathogens (bacteria, viruses, fungi, or parasites) and can spread between hosts.
The major NCDs at GCSE are:
- Cardiovascular disease (CVD) — including coronary heart disease and stroke
- Type 2 diabetes
- Cancer
- Chronic obstructive pulmonary disease (COPD)
What is a risk factor?
A risk factor is anything that increases the probability of developing a disease. Critically, a risk factor is not the same as a cause. Showing that two things change together (correlation) does not prove that one causes the other (causation).
Example: People who smoke have a higher rate of lung cancer than non-smokers. This is a strong correlation. The causal mechanism — carcinogens in cigarette smoke directly damaging DNA in lung cells, triggering uncontrolled division — has been established through experimental evidence. So smoking is both a risk factor AND a proven cause.
Example of correlation without proven causation: Early studies showed a correlation between living near power lines and childhood leukaemia. More rigorous research has not established a clear causal mechanism, so the link remains a correlation.
GCSE exam questions frequently ask you to distinguish between correlation and causation when interpreting data about risk factors.
What are the risk factors for cardiovascular disease?
Cardiovascular disease (CVD) includes coronary heart disease (CHD), in which the coronary arteries supplying the heart muscle become narrowed by fatty plaques (atherosclerosis), and stroke, in which blood supply to the brain is interrupted.
| Risk factor | How it increases CVD risk |
|---|---|
| Smoking | Carbon monoxide reduces oxygen-carrying capacity; nicotine increases blood pressure; chemicals damage artery walls |
| High blood pressure (hypertension) | Damages artery walls, encouraging plaque build-up; makes the heart work harder |
| High blood LDL cholesterol | LDL cholesterol deposits in artery walls to form plaques (atherosclerosis), narrowing arteries |
| Obesity | Raises blood pressure and LDL cholesterol; promotes inflammation |
| Physical inactivity | Raises blood pressure and cholesterol; promotes obesity |
| Diet high in saturated fat and salt | Saturated fat raises LDL; salt raises blood pressure |
| Genetics and family history | Inherited tendency to high cholesterol or hypertension |
| Age and sex | Risk increases with age; males at higher risk at younger ages |
What causes type 2 diabetes?
In type 2 diabetes, cells throughout the body become less responsive to insulin (insulin resistance). The pancreas initially compensates by producing more insulin, but over time it cannot keep up, and blood glucose levels remain persistently high — a condition called hyperglycaemia.
Key risk factors:
- Obesity — particularly excess fat around the abdomen, which increases insulin resistance
- Physical inactivity
- Diet high in refined carbohydrates and sugar
- Genetics — a strong family history of type 2 diabetes increases risk
- Age — risk increases over 40, though rates in younger people are rising
Type 2 diabetes is a non-communicable disease. It is distinct from type 1 diabetes, which is an autoimmune condition in which the immune system destroys the insulin-producing beta cells of the pancreas.
How do risk factors link to cancer?
Cancer occurs when the mechanisms controlling cell division break down, causing cells to divide uncontrollably and form a tumour. Risk factors for cancer either damage DNA directly or disrupt the regulatory processes that normally stop cells dividing inappropriately.
| Cancer type | Key risk factors |
|---|---|
| Lung cancer | Smoking (carcinogens in smoke); radon gas exposure |
| Skin cancer | UV radiation from sunlight; fair skin; tanning beds |
| Bowel cancer | Diet low in fibre; red and processed meat; obesity |
| Liver cancer | Excessive alcohol; some viral infections (hepatitis B, C) |
| Breast cancer | Genetics (BRCA1/2 gene mutations); hormonal factors; obesity |
Some risk factors interact: smoking combined with heavy alcohol consumption multiplies the risk of several cancers beyond what either factor produces alone.
How do lifestyle changes reduce NCD risk?
Evidence from large population studies (epidemiology) consistently shows that lifestyle modifications substantially reduce NCD risk:
- Stopping smoking reduces the risk of heart disease within a year and lung cancer risk falls over time, approaching non-smoker levels after about 15 years.
- Increasing physical activity lowers blood pressure, improves cholesterol profile, reduces obesity, and improves insulin sensitivity.
- Eating a diet lower in saturated fat and salt, with more fruit, vegetables, and fibre, reduces LDL cholesterol and blood pressure.
- Maintaining a healthy body weight reduces the risk of type 2 diabetes, CVD, and several cancers.
- Limiting alcohol reduces liver disease and several cancers.
These changes cannot eliminate risk entirely — genetics and non-modifiable factors (such as age) still play a role — but they can substantially reduce it.
Frequently asked questions
What is the difference between a risk factor and a cause?
A risk factor is any factor associated with an increased probability of developing a disease. It is identified by observing correlations in data — people with risk factor X get disease Y more often than those without it. A cause is a risk factor for which a biological mechanism has been established: the factor directly produces the biological change that leads to disease. Smoking is both a risk factor for lung cancer (correlation established in the 1950s) and a cause (carcinogens in smoke cause DNA mutations that lead to uncontrolled cell division, confirmed by decades of laboratory and clinical research).
Why is obesity a risk factor for so many different diseases?
Excess body fat, especially visceral fat around the abdomen, is metabolically active — it releases hormones and inflammatory chemicals that raise blood pressure, increase LDL cholesterol, promote insulin resistance, and create a chronic inflammatory state. Chronic inflammation is itself a risk factor for atherosclerosis, type 2 diabetes, and several cancers. Obesity also places mechanical stress on joints, raises cancer risk independently of inflammation, and is associated with sleep apnoea, which raises blood pressure further. This is why obesity is a risk factor for cardiovascular disease, type 2 diabetes, several cancers, and other conditions simultaneously.
Is type 2 diabetes always caused by lifestyle factors?
No. Genetics play a significant role — having a close relative with type 2 diabetes roughly triples your lifetime risk, regardless of lifestyle. Some ethnic groups (South Asian, Black African, and Black Caribbean populations) have higher genetic susceptibility. However, lifestyle factors such as obesity and physical inactivity substantially increase the risk above the genetic baseline, and lifestyle modifications can prevent or delay type 2 diabetes even in genetically predisposed individuals. It is incorrect to say that type 2 diabetes is caused solely by lifestyle choices.
How is CVD treated or prevented medically?
Medical management of CVD risk includes drug treatments that modify risk factors: statins lower LDL cholesterol; antihypertensives lower blood pressure; aspirin reduces platelet aggregation (blood clotting). When coronary arteries are already narrowed by plaques, surgical interventions include coronary bypass surgery (replacing the blocked segment with a vein from elsewhere) and stenting (inserting a metal mesh to keep the artery open). Lifestyle modifications remain the most effective long-term prevention strategy and are recommended alongside medical treatment.
For Socratic GCSE biology with Professor Darwin — tracking a risk factor from the cell to the population — visit aitutors.me.