Non-Communicable Diseases
What Are Non-Communicable Diseases?
Non-communicable diseases (NCDs) are diseases that are not caused by pathogens and cannot be passed from person to person. They are often linked to lifestyle, genetics, or environmental factors.
NCDs are the leading cause of death worldwide. The main types include:
- Cardiovascular disease (heart and blood vessel disease)
- Cancer
- Type 2 diabetes
- Liver disease
- Lung disease (e.g. COPD)
Risk Factors
A risk factor is something that increases the likelihood of developing a disease. Risk factors can be:
- Lifestyle choices (things you can control)
- Genetic predisposition (things you cannot control)
- Environmental factors (where you live and work)
Cardiovascular Disease (CVD)
| Risk factor | How it contributes |
|---|---|
| High-fat diet | Increases blood cholesterol → fatty deposits (atheroma) build up in artery walls → arteries narrow → blood pressure rises |
| Smoking | Carbon monoxide reduces oxygen-carrying capacity of blood; nicotine raises heart rate and blood pressure; chemicals damage artery walls |
| Lack of exercise | Heart muscle weakens; weight gain; blood pressure rises |
| Obesity | Forces the heart to work harder; linked to high blood pressure and Type 2 diabetes |
| High blood pressure | Damages artery walls, increasing risk of blood clots and stroke |
| Genetic factors | Family history of heart disease increases risk |
Cancer
Cancer is the uncontrolled growth and division of abnormal cells. Changes in DNA (mutations) can trigger cancer.
Risk factors:
- Smoking — linked to lung, throat, mouth, and bladder cancer (tar contains carcinogens)
- Obesity — linked to bowel, breast, and kidney cancer
- UV radiation — damages DNA in skin cells → skin cancer (including melanoma)
- Ionising radiation (e.g. X-rays, gamma rays) — can cause mutations
- Viral infections — HPV (human papillomavirus) is linked to cervical cancer; hepatitis B/C linked to liver cancer
- Genetic factors — inherited mutations (e.g. BRCA1/BRCA2 genes increase risk of breast cancer)
Type 2 Diabetes
In Type 2 diabetes, the body's cells become resistant to insulin or the pancreas does not produce enough insulin, so blood glucose levels remain high.
Risk factors:
- Obesity — the single biggest risk factor; excess body fat reduces cell sensitivity to insulin
- Diet high in sugar and fat
- Lack of exercise
- Age — risk increases over 40
- Ethnicity — higher risk in South Asian, African, and Caribbean populations
- Family history (genetic component)
Liver Disease
Risk factors:
- Excessive alcohol consumption — the liver breaks down alcohol, but long-term excess causes cirrhosis (scarring of liver tissue) and liver failure
- Obesity — fat builds up in liver cells (non-alcoholic fatty liver disease)
- Hepatitis viral infections
Interactions Between Risk Factors
Risk factors often interact with each other, meaning the combined effect can be greater than either alone:
- Smoking + obesity → greatly increased risk of cardiovascular disease
- Alcohol + obesity → greatly increased risk of liver disease
- Deprivation (poverty) → poorer diet, more stress, higher smoking rates → increased risk of multiple diseases
- Poor mental health → may lead to substance misuse, poor diet, reduced exercise → increased risk of physical diseases
- Physical disease → can cause or worsen mental health conditions (e.g. chronic pain leading to depression)
Correlation vs Causation
In epidemiological studies:
- A correlation is a relationship between two variables (e.g. countries with higher sugar consumption have higher rates of diabetes)
- Causation means one factor directly causes the other
Important: Correlation does not always mean causation. There may be other factors (confounding variables) involved. Scientists must carry out controlled studies, often with large sample sizes, before concluding causation.
Human and Financial Costs
NCDs have both:
- Human costs — reduced quality of life, pain, disability, shortened lifespan, impact on families and mental health
- Financial costs — NHS treatment costs, loss of earnings, reduced productivity, cost of social care
Exam Tips
- Always distinguish between correlation and causation — this is a common 6-mark question
- Be ready to discuss the interaction between risk factors — examiners like to see that you understand these diseases are multifactorial
- Remember that some risk factors cannot be changed (age, genetics, ethnicity) while others can (diet, exercise, smoking, alcohol)