One in 10 Singaporeans affected by asthma

A recent multi-ethnic Singapore study confirms that asthma is a common disease, affecting more than 10 percent of adults, especially former smokers and those with high body mass index (BMI). Asthma is also associated with worse health-related quality of life (HRQoL), making it a substantial public health concern.

Drawing from the 2016 Singapore Mental Health Study, the researchers retrieved data related to asthma prevalence and correlates in a cohort of 6,107 participants (aged ≥18 years, 49.5 percent men). A total of 789 participants had ever been diagnosed with asthma, yielding a lifetime prevalence rate of 11.9 percent; the current prevalence rate, on the other hand, was 2.6 percent. Asthma onset occurred at a mean age of 12.4 years. [Yale J Biol Med 2021;94:417-427]

“The overall prevalence was slightly higher than a previous study conducted among the Singapore adult population where the prevalence, using a similar methodology, was 10.5 percent,” the researchers said. [Communicable Diseases Surveillance in Singapore 2016]

Such trend was consistent with temporal patterns in asthma prevalence worldwide, they added. This upward trend in asthma could reflect greater awareness of the condition, as well as changes in lifestyle, growing rates of obesity, and increasing urbanization and pollution, particularly in developed countries. [Allergy 2004;59:469-478; BMC Public Health 2012;12:204]

Indeed, analysis of current data showed that current asthma was significantly more common among participants who were overweight (vs normal body mass index: odds ratio [OR], 2.30, 95 percent confidence interval [CI], 1.28–4.14; p=0.01) and obese (OR, 2.35, 95 percent CI, 1.2–4.47; p=0.01), as well as those who were former smokers (vs never smokers: OR, 2.23, 95 percent CI, 1.12–4.45; p=0.02).

Other notable risk factors for current asthma included being of Malay (vs Chinese; OR, 1.96, 95 percent CI, 1.15–3.35; p=0.02) and Indian (OR, 2.16, 95 percent CI, 1.33–3.52; p=0.00) ethnicity. In contrast, participants who were 35–49 years (vs 18–34 years: OR, 0.31, 95 percent CI, 0.14–0.70; p=0.01) and 50–64 years of age (OR, 0.41, 95 percent CI, 0.20–0.85; p=0.02) were significantly less likely to have current asthma.

In turn, the researchers found that current asthma led to significantly worse physical HRQoL physical component score (50.69±0.81 vs 53.39±0.11; p=0.001). No such effect was reported for the mental component score and for lifetime asthma.

Moreover, both current (OR, 4.92; p=0.01) and lifetime (OR, 2.24; p=0.02) asthma were also significantly correlated with bipolar disorder, though causality and directionality of the association remained unclear.

“It was not possible to evaluate the temporality between asthma and bipolar disorder, which is an inherent limitation of the cross-sectional design,” the researchers said.

Other important limitations included the use of self-reports as the basis for asthma and the absence of objective clinical assessments for the disease, which may have led to the under-estimation of the true prevalence of asthma in Singapore.

Nevertheless, “these findings may be potentially useful to policy makers, clinicians, and researchers in designing programmes to address services for asthma,” the researcher said.