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Non-communicable diseases: 2.  Risk factors and how different types of disease can interact with each other

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There are various sections to work through, after 1 they can be read and studied in any order.

Sub-index of notes on non-communicable diseases

(2) Examples of risk factors for non-communicable diseases and how different types of disease can interact

Just a few general points as a 2nd introduction to non-communicable diseases - including when diseases coincide and cause other medical situations - physical conditions or mental health issues.

All diseases have risk factors.

Risk factors are anything that can be associated with an increase in likelihood of developing a non-communicable disease, but that doesn't been you will automatically contract the disease!

They can be often related to a person's lifestyle or whether they are exposed to a pollutant in the environment or place of work - air pollution has always been linked with bronchial and lung diseases including asthma.

Age or gender

Certain medical conditions become more likely to older you get - e.g. arthritis or Alzheimer's disease - these are unavoidable as the body ages, but susceptibility varies from one individual to another.

Males and females have different susceptibilities to certain non-communicable diseases.

Alcohol - a lifestyle choice

Too much a in your alcohol in your diet can cause liver damage e.g. cirrhosis of the liver (scarring of the live). This happens because alcohol is broken down by enzymes in the liver and some of the products of this process are toxic.

With excessive drinking over a long period time results in permanent liver damage - in some cases a liver transplant is required to keep the person alive - needs a donor - may not be available.

Heavy drinking raises blood pressure to increase the likelihood of cardiovascular disease.

Excessive drinking of alcohol can affect brain function, nerve cells are damaged and brain volume decreases.

High alcohol consumption is being linked to cancers of the bowel, liver, mouth and throat.

When pregnant women drink to much alcohol there is an increased risk of health problems for an unborn baby e.g. abnormal foetal brain development.


Quite a few diseases can be linked to genetic factors - what we become from our inherited genes, which may include particular mutated alleles.

Unfortunately, you can inherit faulty genes that you a person more susceptible to cancer or coronary heart disease.

e.g. mutations to the BRCA genes have been linked to increased chance of women developing breast cancer or ovarian cancer.

Immune system responses

The presence of a pathogen infection in your body can trigger an allergic reaction from your immune system e.g. asthma sufferers experience more intense symptoms or skin rashes.

You can also have problems if a disease you have lowers your immune system response and you become susceptible to another disease. See HIV virus infection as an example.

Other lifestyle choices and your personal situation


Lack of regular exercise is one of several factors that increase your chance of contracting cardiovascular disease - especially if you have a poor diet too rich in fatty and sugary foods leading to obesity - overweight.

Physically inactive people are more likely to develop high blood pressure and heart disease, and an increased risk of certain kinds of cancer.

See The human circulatory system - causes/treatment of cardiovascular disease


Eating a good balanced healthy diet helps maintain your body in good shape and your immune system to fight communicable disease infections and reduce the risk of contracting non-communicable diseases such as cardiovascular disease and cancers.

The human circulatory system - including the causes and treatment of cardiovascular disease

If you do not get the right balance of nutrients in your diet, you have a condition called malnutrition.

The poorer you diet (poor nourishment), the more susceptible you are to these kinds of diseases and mental health issues.

Eating a balanced nutritious diet, not too high in fats and sugars, plenty of minerals and vitamins from whole grains, fruit and vegetables.

Lack of vitamin C in your diet causes scurvy, a non-communicable disease with harmful consequences.

e.g. lack of vitamin C inhibits the body's ability to make collagen - an important protein found in bone and tendon tissue.

Symptoms of scurvy include painful joints and muscles and bleeding gums.

Vitamin D is both a nutrient in food we eat and a hormone our bodies make in our skin cells from the action of sunlight.

It is a fat-soluble vitamin that helps the body absorb and retain calcium and phosphorus; both are critical for building bone.

Laboratory studies show that vitamin D can reduce cancer cell growth, help control infections and reduce inflammation.

Interestingly, many of the body’s organs and tissues have receptors for vitamin D, which suggest important roles for Vitamin D other than bone health.

Lack of vitamin D may help your body fight the covid-19 viral infection, people low in vitamin D seemed to have been more susceptible to the disease.

A diet too high in fat an sugar can lead to obesity - being overweight makes your more susceptible to non-communicable diseases such as cardiovascular disease and type 2 diabetes - the latter can often be dealt with by changing to a more healthy balanced nutritious diet.

Smoking - completely avoidable to reduce your chance of developing lung cancer.

BUT, smoking is now linked to cardiovascular disease and lung diseases including cancer.

Chemicals in tobacco smoke harm your blood cells and can damage the function of your heart and the structure and function of your blood vessels.

Smoking reduces the body's defences against particles you breathe in.

Substances in tobacco smoke cause damage to lung tissue. Cigarette smoke contains four potentially harmful substances - (i) carbon monoxide, (ii) nicotine, (iii) particulates and (iv) tar.

This damage increases your risk of atherosclerosis - a disease in which a waxy substance called plaque builds up in the arteries.

(i) Carbon monoxide molecules (CO) combines with haemoglobin more strongly than do oxygen molecules (O2).

This displaces oxygen from oxygenated haemoglobin and reduces the oxygen supply to your cells affecting your respiration.

(ii) Nicotine makes smoking addictive.

Nicotine in cigarette smoke increases heart rate which increases blood pressure - increasing the chance of a heart attack, stroke or blood clot formation. Increased blood pressure damages the walls of arteries which contributes to the build up of fatty deposits on the walls of the arteries - leading to heart disease and circulation problems which further increase the risk of a stroke or heart attack when the blood supply to the brain or heart is cut off.

(iii) Your lungs are also subjected to fine particulates that lodge in the alveoli of the lungs - the latter will affect the efficiency of lungs to deliver oxygen to the cells of your body.

Cigarette smoking causes inflammation of the lining of the bronchi and bronchiole tubes in the lungs giving you chronic bronchitis - persistent cough, wheezing i.e. breathing problems!

The damage builds up and can eventually lead to bronchitis - a disease that inflames the lining of the bronchial tubes and also emphysema - a disease that destroys the alveoli (air sacs) in the lungs.

(iv) The cells in the lining of the lungs can be coated in tar (which also contains carcinogens).

The tar covers the cilia hairs on the lining of airways inhibiting from moving mucous along, which sticks to the lining of the airways making you cough as you try to get rid of the mucous - 'smokers cough'.

This causes various serious lung conditions - breathing problems because of less efficient oxygen intake, mutations of the DNA of lung cells to form tumours which can become cancerous. Smoking is now related to cancer of the  mouth, oesophagus and throat as well as the lungs.

how respiratory system protects body ciliated cells goblet cells mucus traps dust particles cilia moves them along gcse biology igcse

Cells that line the trachea and bronchi have cilia and others produce mucus.

You can think of it as the mucous membrane.

The cilia, hair-like structures, can move the mucous along from the lungs up to the nasal passage and back of the throat where it can be swallowed, coughed out or blow your nose, into a tissue!

Note that smoking can damage and paralyse the cilia reducing the ciliated cell's capacity to remove harmful particles, so another reason why smokers are more susceptible to respiratory diseases.

When pregnant women smoke there is an increased risk of health problems for an unborn baby.

I can't understand why anyone smokes cigarettes these days, but they do!


Asthmatics are people who suffer from asthma because their lungs are much too sensitive to certain materials.

If an asthmatic breathes these substances in the muscles around the bronchioles contract, narrowing the airways in the lungs.

The lining of the airways becomes inflamed and fluids build up in the airways making it harder to breathe - this what is called an asthma attack.

The symptoms are difficulty in breathing, wheezing and a feeling of tightness in the chest.

When an asthmatic attack occurs, e.g. symptoms above, the asthmatic can treat themselves with an inhaler containing drugs that open up the airways to allow normal efficient breathing.

Access to your needs?

The risk of a non-communicable disease starting and progressing increases if you have limited access to good healthcare systems and health education.

When you have access to a quality healthcare system, your medical condition is more likely to be diagnosed and receive appropriate treatment.

Education provides you with knowledge about how non-communicable diseases develop and strategies for prevention e.g. diet and exercise.

Malnutrition means lack of proper nutrition, caused by not having enough to eat, not eating enough of the right things, or being unable to use the food that one does eat.

Usually no problem in rich developed countries - your choices, BUT not so for people living in poorer underdeveloped countries - an undernourished body is more likely to be fatigued and more susceptible to the effects of infections and non-communicable diseases.

e.g. to help prevent or reduce the risk of non-communicable diseases in the first place - an you afford to buy healthy food? Is 'healthy shopping' readily available?

If you have contracted a non-communicable disease, do you have access to appropriate medicines?

Perhaps surprisingly?, non-communicable diseases are more likely with people of higher income in developed countries because they can afford to buy richer food higher e.g. in saturated fats - obesity related.

However, ALSO, people from poorer areas are poor likely to have a poorer diet (not balanced) and exercise less. Therefore in deprived areas, you find higher rates of cardiovascular disease, obesity, type 2 diabetes due to less healthy lifestyles.

Statistics and a note of caution!

Medical scientist do their best correlate data connecting risk factors with disease incidence.

However, correlation doesn't simply mean you can relate incidence to cause.

Just because you eat a poor diet and have little exercise doesn't mean to say you automatically get e.g. cardiovascular disease (CVD).

Your diet and lack of exercise does not cause CVD directly. What these two factors cause is high blood pressure and increase in the blood levels of bad LDL cholesterol - and it is these which actually cause the CVD.

Mental health and stress

If can develop a mental health condition such as depression while enduring some physical health problem e.g. lack of mobility reducing your ability to participate fully in everyday life.

If you are constantly under mental stress e.g. 'high-powered' job or caring for a very sick relative, then your physical well-being can be affected - ulcers can develop or a mental health condition like extreme anxiety - both of which are non-communicable.

When you are stressed, hormones are released, your blood vessels constrict (narrow) and your blood pressure is raised.

Stress can lead to depression, and increased risk of obesity and diabetes, also increasing the risk of cardiovascular disease, diabetes and Alzheimer's disease.


Obesity usually involves lifestyle factors, but 'body chemistry' is naturally quite variable and not all down to lifestyle.

Poor diet and 'over-eating' lead to excess weight in the body - obesity!

This increases your susceptibility to type 2 diabetes when your body is less responsive to your own insulin and reduced control of blood sugar levels - which can be very dangerous.

Obesity can also affect your breathing - reduces your respiratory function.

Obesity is a risk factor in other non-communicable diseases e.g. cardiovascular disease and type 2 diabetes.

Viral infection

Some types of cancer are triggered by particular viral infections.

This is a communicable disease causing the development of a non-communicable disease.

Keywords, phrases and learning objectives for this part on risk factors and disease interactions

Be able to describe and discuss non-communicable diseases in terms of risk factors such as age, gender, consumption of alcohol, genetic factors, diet, smoking, lack of exercise, malnutrition, viral infections, obesity and stress.

Understand how different types of disease interact with each other.

Appreciate the importance and need for access to good medical care and have good mental health.



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