The results carry potential implications in the management of asthma and allergic rhinitis in tropical urban environments.
The new study, which was conducted on some 8,000 participants, revealed that close to 15% of Singapore’s adult population is affected by asthma and nearly 40% is troubled by allergic rhinitis. According to the World Health Organization, it is estimated that approximately 300 million people suffer from asthma worldwide and even more are affected by allergic rhinitis. Both conditions are now increasingly common in Southeast Asian populations.
“Given the increasing prevalence of airway allergic diseases in Singapore and Southeast Asian countries, this study is truly a breakthrough in understanding why there are such high numbers of allergic rhinitis patients in Singapore. Knowing the cause is the first step in developing more effective interventions to improve the quality of life for asthma and allergic rhinitis sufferers,” said Research Associate Professor Wang De Yun, from the Department Otolaryngology at the NUS Yong Loo Lin School of Medicine. He co-led the study with Adjunct Associate Professor Olaf Rötzschke from NUS’ Department of Microbiology, who is also a Principal Investigator at SIgN.
Their findings address the widening problem of allergy and asthma in tropical countries. The results suggest that changes in lifestyle resulting in more time spent indoors increase our exposure to high loads of house dust mite allergens, which translates into a dominant cause of respiratory allergic diseases in Southeast Asia. With this knowledge, scientists can develop more effective allergen-specific desensitisation strategies as well as environmental interventions aiming at the reduction of the house dust mite load.
“Rather than relying on statistics from other countries, we have managed to pinpoint the cause of airway allergies in Singapore. We believe that results from this study will help to understand the differences of allergies in the tropics and other parts of the world,” said Assoc Prof Rötzschke.
“Knowledge of the allergic trigger, together with a nearly complete sensitisation of the local population provides the perfect basis for the future exploration of the molecular and genetic factors that ultimately determine if the response to an allergen progresses into an allergic syndrome,” he added.
Eighty-percent of those surveyed were reactive to house dust mites, and showed only a slight reactivity to 11 other common allergens that they were exposed to. Participants’ reactivity was measured via a skin-prick test or by measuring the level of allergy-associated Immunoglobulin E (IgE), a class of antibodies that is raised upon reaction to an allergen. The high rate of reactions from house dust mites are strongly correlated with increased rates of allergic rhinitis and asthma in Singapore.
The study further found that migrants from non-tropical countries had low sensitisation rates for house dust mites when they first arrived in Singapore, but these rates increased as they spent more time here. This increase was accompanied by an increase in airway allergies. Migrants from countries with climates similar to Singapore, such as Malaysia, showed comparable rates as Singaporeans, pointing again to house dust mites as the primary environmental cause.
National University of Singapore.