T.N. Tan

The prevalence of asthma and allergies in Singapore; data from two ISAAC surveys seven years apart

Background and Aims: Over the past few decades, the prevalence of asthma has been increasing in the industrialised world. Despite the suggestion of a similar increase in Singapore, the 12 month prevalence of wheeze among schoolchildren in 1994 was 2.5-fold less than that reported in western populations. It was hypothesised that with increasing affluence in Singapore, the asthma prevalence would further increase and approach Western figures. A second ISAAC survey was carried out seven years later to evaluate this hypothesis. Methods: The cross-sectional data from two ISAAC questionnaire based surveys conducted in 1994 (n = 6238) and in 2001 (n = 9363) on two groups of schoolchildren aged 6–7 and 12–15 years were compared. The instruments used were identical and the procedures standardised in both surveys. Results: Comparing data from both studies, the change in the prevalence of current wheeze occurred in opposing directions in both age groups—decreasing in the 6–7 year age group (16.6% to 10.2%) but increasing to a small extent in the 12–15 year age group (9.9% to 11.9%). The 12 month prevalence of rhinitis did not change; there was an increase in the current eczema symptoms in both age groups. Conclusion: The prevalence of current wheeze, a surrogate measure of asthma prevalence, has decreased significantly in the 6–7 year age group. Eczema was the only allergic disease that showed a modest increase in prevalence in both age groups.

Distinct pattern of commensal gut microbiota in toddlers with eczema.

Background: Recent studies have demonstrated differences in the composition of gut microbiota in infants with and without allergic diseases, particularly eczema. Methods: A case-control study involving 21 toddlers (age 3.0 ± 0.5 years) with and 28 age-matched toddlers without eczema was conducted. Four groups of aerobic gut microbiota were identified and quantitated in stool samples grown on selective media. Three groups of anaerobes were enumerated by fluorescent in situ hybridization followed by quantitative flow cytometry. We also performed molecular typing of lactic-acid-producing bacteria (LAB) and enterococcal isolates to facilitate detailed analysis at species level by bacterial 16S rDNA sequencing. Results: Toddlers with eczema harbored significantly lower counts of Bifidobacterium [(median 0.14 (25th and 75th percentile: 0.04 and 0.47) vs. 0.71% (0.16, 1.79) of cells acquired, p = 0.003)] and Clostridium [(0.28 (0.09, 0.78) vs. 0.83% (0.35, 1.82) of cells acquired, p = 0.012)] but significantly higher counts of total LAB [7.3 (6.1, 8.5) vs. 5.7 (4.4, 7.3) log CFU/g, p = 0.006] in particular enterococci [6.3 (4.8, 7.4) vs. 5.0 (3.4, 6.4) log CFU/g, p = 0.018]. There was no significant correlation between eczema severity score and bifidobacterial counts. Conclusion: The results further confirm previous reports that the gut microecosystem differs between children with and without eczema and extend them beyond infancy.

Prevalence of allergy-related symptoms in Singaporean children in the second year of life

This study describes the cross‐sectional prevalence of symptoms associated with eczema (chronic itchy rash), asthma (wheeze), and allergic rhinitis (rhinoconjunctivitis) in 1026 subjects between 18.5 and 23 months old (median age is 21 months) in Singapore. The first 2 yr cumulative prevalence of chronic itchy rash, wheeze, and rhinoconjunctivitis were 22.1% (n = 227), 22.9% (n = 235), and 8.4% (n = 86) respectively. In total, 42.2% (414 of 979) reported ever having any of these symptoms. Eczema, although prevalent, was diagnosed only in 34.4% (n = 78) of children with chronic itchy rash. Children with this eczematous rash were also more prone to wheeze (cOR = 2.0, 95% CI: 1.2–3.0) and rhinoconjunctivitis (cOR = 2.0, 95% CI: 1.4–2.8). Similarly, subjects who reported rhinoconjunctivitis and chronic itchy rash were 2.4 times (95% CI: 1.6–3.6) and 1.4 times (95% CI: 1.0–2.0) more at risk of wheezing respectively. Family history of allergy was a significant risk factor for chronic itchy rash (aOR = 1.8, 95% CI: 1.3–2.4) and wheeze (aOR = 1.7, 95% CI: 1.3–2.4). Thus, symptoms related to allergy were already prevalent during the second year of life. Significant proportions of these symptoms are likely to be due to true atopy as strong relationship with familial history and comorbidity with other potential allergic symptoms were observed.

Endotoxin Levels in Rural Thai and Urban Singaporean Homes

Background: Exposure to dust endotoxin and allergens in early childhood may influence the development of allergic diseases. Aims: This study aimed to evaluate dust endotoxin and dust mite allergens in urban Singapore and rural Thai homes of young children and study potential environmental influences. Methods: Mattress dust endotoxin and Der p 1, Der f 1, group 2 (Der f 2 and Der p 2) and Blo t 5 allergen levels were quantified in 101 infant mattress dust samples, 51 from urban Singapore and 50 from rural Thailand. Comprehensive questionnaires on the home environment and cleaning practices were completed. Results: Endotoxin levels in rural Thailand were significantly higher than in urban Singapore (geometric mean 26,334.12 ± 4.60 and 18,377.85 ± 2.52 endotoxin units/g, respectively; p = 0.032). In contrast, higher levels of Der f 1 (p = 0.02), group 2 (p < 0.01) and Blo t 5 (p < 0.01) allergens were found in Singapore homes compared with rural Thai homes. Multiple logistic regression analysis showed that the use of detergents (p = 0.001) and disinfectants (p = 0.024) to clean floors and mattress protectors (p = 0.021) were independently associated with lower endotoxin levels. Conclusion: Endotoxin levels are higher in rural compared with urban homes in South East Asia. The reverse was true for dust mite allergen levels. Certain identifiable home environmental conditions and practices accounted for the differences in endotoxin levels.