Does early indoor microbial exposure reduce the risk of asthma? The Prevention and Incidence of Asthma and Mite Allergy birth cohort study.

BACKGROUND: Exposure to microbial agents might inhibit the development of atopy and asthma. OBJECTIVE: We measured the association between microbial exposure assessed at 3 months and the development of atopic sensitization and doctor-diagnosed (DD) asthma and wheeze in the first 4 years in a birth cohort study of children with atopic mothers. METHODS: Endotoxin, fungal (1-->3)-beta-D-glucans, extracellular polysaccharides from the genera Penicillium and Aspergillus (EPS-Pen/Asp), and dust on living room floors were measured at 3 months of age. Serum IgE levels against common allergens were determined at 1 and 4 years, and questionnaire information about respiratory morbidity was collected yearly. RESULTS: Microbial levels in mattresses were low and not associated with serum IgE levels, DD asthma, and wheeze. Floor levels of biocontaminants and dust, on the other hand, were inversely associated with DD asthma, being most pronounced for endotoxin (odds ratio [OR], 0.40; 95% CI, 0.21-0.77) and EPS-Pen/Asp (OR, 0.42; 95% CI, 0.18-0.99). Mutual adjustment for other exposures did not significantly alter the results for endotoxin and only moderately affected the results for EPS-Pen/Asp. Persistent wheeze was also consistently less common in the high-exposure group, being significant only for EPS-Pen/Asp (OR, 0.37; 95% CI, 0.15-0.96). Transient wheeze and wheeze in the past 12 months were also reduced, but effects were smaller and not significant. Relationships with serum-specific IgE levels, which could only be assessed in 41% at age 4 years, were less pronounced and statistically significant only for EPS-Pen/Asp. CONCLUSIONS: Early exposure to common microbial contaminants, including fungal agents, might protect against asthma. CLINICAL IMPLICATIONS: Microbial exposure in early life might protect against asthma and might constitute a novel target for prevention.

Lung function decrease in relation to pneumoconiosis and exposure to quartz-containing dust in construction workers.

BACKGROUND: Prevalence of exposure related respiratory symptoms and decreases in lung function are unknown among quartz dust exposed construction workers. METHODS: In a cross-sectional study (n = 1335), the occurrence of respiratory symptoms, was recorded and spirometric lung function was measured. Results were associated with exposure data and presence of radiographic abnormalities and compared with a reference population. RESULTS: Pneumoconiosis (profusion category 1/1 or greater) was associated with increased risks of FEV(1) and FVC values in the lowest 5% group, and with group-based decreases of 270 ml/s and 180 ml, respectively. Average lung function of construction workers was somewhat lower compared to a Dutch reference population. Lung function was not associated with exposure, except for a reduction in FVC of 5 ml per year for those with higher exposure. CONCLUSIONS: In quartz dust exposed construction workers obstructive and restrictive lung function loss was detected.

The prevention and incidence of asthma and mite allergy (PIAMA) birth cohort study: design and first results.

The Prevention and Incidence of Asthma and Mite Allergy (PIAMA) birth cohort study was initiated in 1996. Children born to allergic mothers were enrolled in a double-blind placebo-controlled trial for evaluating the use of mite-impermeable mattress and pillow covers. Children born to allergic and non-allergic mothers were enrolled in a 'natural history' study to assess the role of environmental and dietary risk factors for the development of allergic disease in childhood. Recruitment started by distributing a validated screening questionnaire among >10,000 pregnant women during their first visit to a prenatal health clinic. Allergic mothers-to-be were invited to participate in the intervention study. Allergic, and a random sample of non-allergic, mothers-to-be were invited to participate in the 'natural history' arm of the study. In the intervention study, homes were visited before birth, 3 months after birth, and 12 months after birth for the collection of dust samples from floors and mattresses. In addition, the homes of about one-third of the children in the 'natural history' part of the study were visited for dust collection when the children were 3 months of age. The intervention study started with 855 participants and the 'natural history' study with 3,291 participants. Follow-up at 3 years of age has now been completed with satisfactory compliance (>90%). A medical investigation and home visit at 4years of age are nearing completion. Preliminary results show that mite-allergen levels were lower than found in previous Dutch studies, and that the intervention measure had a significant effect on mite-allergen levels, without important clinical benefits up to age 2 years old. The allergic families lived in homes with fewer 'triggers' such as pets, smoking and carpets than the non-allergic families, regardless of the intervention. The ongoing PIAMA cohort study will probably reveal useful information concerning effects of allergen load and reduction in the setting of a relatively low mite-allergen exposure, as well as other variables on the development of allergic manifestions and asthma.