The causes of asthma are not yet fully understood . Asthma is usually caused by a mixture of hereditary factors (those you are born with) and environmental risk factors (those you are exposed to), but how these factors work together is still largely unknown.
There is nothing you can do about some risk factors other than monitoring them. If the risk factors are related to lifestyle, you can sometimes take action to improve your health.
Asthma risk factors that you cannot change
- Family history
Asthma tends to run in families, which means that you are more likely to develop asthma if someone in your family already has it.
Many patients with asthma, either allergic or non-allergic, also have rhinitis (sneezing, runny or itchy nose or the feeling of a blocked nose), and 10–40% of patients with allergic rhinitis have asthma.
People with allergy are more likely to develop asthma than people without allergy. Asthma is more frequent in people with an allergic condition, such as allergic rhinitis, atopic dermatitis or food allergy. Indeed, all these conditions are caused by a response of our immune system that causes inflammation in the target organ (nose, skin or lungs).
- Exposure to air pollution
Exposure to air pollutants increases the risk of developing asthma. Pollutants may be linked to various sources, for example, industrial activities, transport, agriculture, domestic heating/cooling, hazardous chemicals in the work place, smog, etc. People living in urban areas are more likely to develop asthma given their proximity to these sources of pollution.
- Viral respiratory infections
Respiratory infections, such as bronchiolitis, respiratory syncytial virus and rhinovirus during childhood can cause wheezing. Some children who experience viral respiratory infections in early life may develop asthma.
- Pre-term babies
Being born pre-term is not a risk factor for the development of asthma per se, but it is linked to an increased risk of developing persistent airflow limitation .
Asthma risk factors that you may avoid
- Smoking and vaping
Smokers have a higher risk of developing asthma than non-smokers because cigarette and e-cigarette smoking lead to lung irritation, and to an increased risk of asthma symptoms and attacks.
- Exposure to second-hand smoke
People exposed to second-hand smoke during childhood, or whose mother smoked during pregnancy, are more likely to develop asthma.
- Exposure to asthma triggers.
Exposure to certain chemicals, gases or allergens in the work place may lead to lung inflammation, thereby increasing the risk of developing occupational or work-related asthma. Occupational asthma is more frequent in sectors that use chemicals, such as farming, hairdressing and manufacturing, or among professionals that are often exposed to allergens, such as bakers, millers or farmers. If asthma symptoms develop at work or worsen at work, you should be referred for specialist investigation (if available) as soon as possible, and avoid ongoing exposure.
- Childhood obesity
Being overweight or obese is a risk factor for childhood asthma and wheezing. In rare cases, obesity may be due to genetic predisposition, therefore it is always recommended to look for medical advice.
- Sly PD, Bush A. From the Cradle to the Grave: The Early-Life Origins of Chronic Obstructive Pulmonary Disease. Am J Respir Crit Care Med. 2016 Jan 1;193(1):1-2