House-dust mites and mattresses

Background: Despite considerable efforts to develop anti dust mite strategies, surprisingly few studies have evaluated the allergen content in different types of mattresses in everyday use. This study investigated the presence of mite feces (an indicator of mite allergens) in foam and spring mattresses. Methods: The homes of 152 schoolchildren in Northern Norway were investigated. Dust samples were collected in a standardized way from 24 foam mattresses without covers, 68 foam mattresses with covers, and 24 spring mattresses, and the presence of mite feces detected by a guanine colorimetric paper test (Acarex). Results: We found mite feces in 15 (40.5%) of the dust samples from the foam mattresses without covers and 18 (26.3%) of the foam mattresses with covers. Only three (12.5%) of the spring mattresses contained detectable amounts of feces. Signs of dampness, age of mattress, cleaning of mattress, frequency of vacuuming the bedroom, mechanical ventilation, bedroom temperature and bedroom relative humidity were associated with the presence of mite feces. After adjustment for relevant confounders, the risk of finding mite feces was four times higher in foam compared to spring mattresses (odds ratio 4.0, 95% confidence interval (CI) 1.1-15.1), and eight times higher for the foam mattresses without cover (OR 8,1, 95% Cl 1.8-36.9). Conclusion: A simple replacement of foam mattresses with spring mattresses may reduce the exposure to house-dust-mite allergens.