1 The World Health Organisation (WHO) estimates that 300 million people around the world suffer from asthma.

2 According to WHO, the biggest risk factors of developing asthma are exposure to indoor allergens such as house dust mites in bedding, carpets and stuffed toys, outdoor allergens like pollen and mould and tobacco smoke.

3 Haze aggravates asthma symptoms. Professor Philip Eng, a senior consultant respiratory physician at Mount Elizabeth Hospital, said that haze brought on by fires contains many chemicals such as sulphur dioxide, nitrous dioxide and particulate matter. These three by themselves cause inflammation and narrowing of the airways, hence worsening asthma.

That is why one should avoid strenuous outdoor activities when the PSI level is high.

4 Asthma can occur among the elderly. Dr Khoo See Meng, a consultant at the division of respiratory & critical care medicine at the University Medicine Cluster at National University Hospital, said: 'Among the elderly, the presence of multiple medical conditions can sometimes cause confusion in the diagnosis of asthma.

'It may be difficult to distinguish asthma from other causes of breathlessness, like heart failure, in the elderly. A careful history and physical examination are usually needed to clarify the picture.'

5 According to information provided by KK Women's and Children's Hospital, common symptoms of asthma are wheezing, cough, shortness of breath and chest tightness. Coughs generally occur at night or early in the morning.

This article was first published in Mind Your Body, The Straits Times.