Asthma in every fifth child in Oslo, Norway: a 10-year follow up of a birth cohort study

BACKGROUND

The western world's increase in childhood asthma is suggested to level off. We aimed to investigate asthma prevalence in 10-year-old children within the prospective birth cohort Environment and Childhood Asthma (ECA) Study in Oslo established in 1992/1993.

SUBJECTS AND METHODS

Six hundred and sixteen (77%) of 803 children (mean age 10.9 +/- 0.9 (SD) years) with lung function measurements at birth were reinvestigated at age 10 years. At birth they corresponded to the entire birth cohort (n = 3754) regarding gender, socio-demographic factors, parental allergic diseases, pet keeping and maternal smoking. Results from structured parental interview, spirometry, and skin prick test for inhalant and food allergens are presented. Asthma definition required minimum two positive criteria, (i) doctor's diagnosis of asthma, (ii) wheeze and/or chest tightness, (iii) use of anti-asthmatic treatment. Current asthma required asthma definition plus either (ii) and/or (iii) in the last 12 months, and/or > or = 10% fall in forced expired volume in 1 s after treadmill running.

RESULTS

Lifetime prevalence of asthma was 20.2%; current asthma 11.1%, doctor diagnosis of asthma 16.1% and wheezes ever 30.3%. Allergic sensitization (29.3% overall) was more common among children with current (56.3%) compared to asymptomatic (last 12 months) (26.0%) or no asthma (27.6%) (P < 0.001). Boys more often than girls had current asthma (14.4 vs 7.1%, P = 0.004), wheeze ever (36.9 vs 22.5%, P = 0.002) and allergic sensitization (36.2 vs 22.1%, respectively, P < 0.001).

CONCLUSION

Childhood asthma apparently continues to increase in Oslo, having affected every fifth 10-year-old child.

Severity of obstructive airways disease by age 2 years predicts asthma at 10 years of age

BACKGROUND

Predicting school-age asthma from obstructive airways disease (OAD) in early life is difficult, even when parental and children's atopic manifestations are taken into consideration.

OBJECTIVE

To assess if the severity of OAD in the first 2 years of life predicts asthma at 10 years of age.

METHODS

From a nested case control study within the Environment and Childhood Asthma study, 233 2-year-old subjects with recurrent (> or = 2 episodes) bronchial obstruction (rBO+) and 216 subjects without bronchial obstruction (rBO-) underwent clinical examination, parental interview, treadmill test and metacholine bronchial hyperresponsiveness (BHR) measurement at 10 years. A severity score at 2 years was calculated by frequency, persistence of bronchial obstruction and hospital admissions because of OAD.

MAIN OUTCOMES

Current asthma at 10 years (asthma with symptoms and/or asthma medication during the past year and/or positive treadmill test). Secondary outcome was metacholine BHR at 10 years.

RESULTS

Compared with rBO- subjects, adjusted odds ratio (95% CI) of current asthma among rBO+ was 7.9 (4.1, 15.3), and among rBO+ with a severity score of > 5, 20.2 (9.9, 41.3). In receiver operated characteristic analysis, positive and negative predictive values demonstrated the applicability and value of the score, with an optimal cut-off at severity score 5. Children with severity score > 5 had severe BHR more often (PD20 metacholine < 1 micromol) than children with a lower or 0 score (p = 0.0041).

CONCLUSION

Using a simple scoring system, a high severity score of OAD by 2 years of age is a strong risk factor for, and may predict, current asthma at 10 years of age.

Childhood asthma and early life exposure to indoor allergens, endotoxin and beta(1,3)-glucans

BACKGROUND

Divergent results have been reported regarding early life exposure to indoor environmental agents and the risk of asthma and allergic sensitization later in life.

OBJECTIVE

To assess whether early exposure to indoor allergens, beta(1,3)-glucans and endotoxin modifies the risk of allergic diseases at 10 years of age.

METHODS

The concentrations of mite, cat and dog allergens, endotoxin and beta(1,3)-glucans were determined in dust from the homes of 260 two-year-old children with lung function measured at birth (tidal flow volume loops) in the Environment and Childhood Asthma study in Oslo. At 10 years, the health status was assessed in a follow-up study including a structured interview of the parents and an extended clinical examination.

RESULTS

Cat and dog keeping at 2 years of age was reported in 6.5% and 5.5% of the families, respectively. Mite allergens were detected in only 4/260 dust samples. The adjusted odds ratio for asthma at age 10 was 1.20 (95% confidence interval: 1.01-1.43) and 1.22 (1.02-1.46) for bronchial hyperresponsiveness (BHR) per 10 microg/g dust increase in cat allergen exposure at 2 years of age. No association was seen with allergic sensitization. Moreover, endotoxin and beta(1,3)-glucan exposure did not modify the risk of asthma or allergic sensitization. None of the measured environmental factors were associated with lung function at 10 years of age or a relative change in lung function from birth.

CONCLUSION

In a community with a low prevalence of pet keeping and low mite allergen levels, exposure to cat allergens early in life increased the risk of late childhood asthma and BHR, but not the risk of allergic sensitization. No risk modification was seen for dog allergens, endotoxin and beta(1,3)-glucans.

Effects of calprotectin in avridine-induced arthritis

Plasma levels of calprotectin correlate with disease activity and clinical assessments of arthritis in various rheumatic diseases, and high levels have been demonstrated in the synovial fluid of patients with rheumatoid arthritis. However, the role of calprotectin in rheumatic inflammation is unclear. The purpose of the present study was to investigate potential intra-articular effects of calprotectin. Calprotectin was injected into joints of healthy male Lewis rats and into joints of rats in the latency period before onset of avridine-induced arthritis. In addition, a group of animals had IgG antibodies to rat calprotectin injected into joints before onset of avridine-induced arthritis. Injection of 0.2 or 10 micrograms calprotectin into the ankles of healthy male Lewis rats resulted in histologically minor and reversible inflammatory changes, but without any circulating antibodies to calprotectin. Furthermore, animals with 40 micrograms calprotectin injected into ankles before the expected onset of avridine-induced arthritis had lower scores for cellular infiltration than were seen in control joints. This difference did not quite reach statistical significance in the two-sided test used. However, the induced arthritis increased in joints injected with IgG antibodies to calprotectin. These findings may indicate that increased local concentrations of calprotectin are partially protective against avridine-induced arthritis. In contrast, reduced local concentrations appear to exacerbate the severity of arthritis. Calprotectin may thus be involved in the regulation of inflammatory processes in joints.

Diagnostic value of exhaled nitric oxide in childhood asthma and allergy

Fractional exhaled nitric oxide (FE(NO) ) has been proposed as a diagnostic test of asthma. We aimed to investigate in a population based birth cohort of children the usefulness of FE(NO) as a diagnostic tool. The 10-yr follow up of the Environment and Childhood Asthma Study in Oslo included 616 children representative of the prospective birth cohort. Both FE(NO) (single breath technique) and skin prick test (SPT) were measured in 331, limited at the time by equipment availability. Structural parental interview, spirometry, methacholine challenge and exercise test were performed. FE(NO) was significantly elevated in children with current asthma (geometric mean 9.6 (95% confidence interval (CI) (6.9, 13.4) p.p.b.) compared with healthy children (5.8 (5.4, 6.3) p.p.b.; p < 0.001). FE(NO) was highest among children with current allergic asthma (asthma and positive SPT) (14.0 (8.9, 22.1) p.p.b.), whereas children with non-allergic asthma (6.1 (4.0, 9.2) p.p.b.) had comparable FE(NO) levels to healthy children (p = 0.99). Allergic sensitization was most closely associated with FE(NO) . A FE(NO) cut-off value of 20.4 p.p.b. had a high specificity (0.97), but a low sensitivity (0.41) and a Positive Likelihood Ratio of 16.1 for current allergic asthma. In the present childhood population-based study, high FE(NO) levels were closely associated with current allergic asthma and not with current asthma without allergic sensitization. Estimating the individual predictive probability of having asthma by use of FE(NO,) improves the diagnostic utility of the test.

HLA Dr-Dq haplotypes and the TNFA-308 polymorphism: associations with asthma and allergy

BACKGROUND

The HLA (human leukocyte antigen) class II genes DQB1 and DRB1 and the Tumor Necrosis Factor alpha gene (TNFA) within the HLA complex (chromosome 6p21) have been associated with asthma and allergy. Due to the strong linkage disequilibrium characterizing this complex and the multiple asthma/allergy expressions, we aimed to determine which of these genes were primarily involved in specific asthma/allergy traits.

METHODS

The DRB1-DQB1 alleles and TNFA-308 polymorphism were genotyped in 959 children from the Environment and Childhood Asthma study and analyzed for possible associations with allergic and non-allergic asthma (with/without at least one positive skin prick test for allergens) and specific allergic sensitization, as well as bronchial hyperresponsiveness and total IgE, using both allele and extended haplotype analyses.

RESULTS

Different genes within the HLA complex were associated with separate asthma and allergy traits. Nonallergic asthma was associated with both the TNFA-308A allele [Odds ratio (OR) 1.7 (1.3-2.3)] and DRB1 03 allele [OR 1.6(1-2.6)], but extended DRB1 03-TNFA-308 haplotype analysis suggested that the DRB1-DQB1 association was secondary to linkage disequilibrium with the TNFA-308 polymorphism. Allergies were associated with HLA class II alleles only; birch sensitization with DQB1 0603-DRB1 13 [OR 2.3 (1.4-4.0)] and mugwort sensitization with DQB1 0609-DRB1 13 [OR 7.1 (1.9-27.0)] and DQB1 0501-DRB1 01 [OR 2.0 (1.0-4.0)].

CONCLUSIONS

Our data suggests that asthma is not associated with DRB1 or DQB1 but rather TNFA or a gene(s) in linkage disequilibrium, while sensitization to specific allergens is associated with particular alleles at the DQ and/or DR loci. A novel association between DQB1 0603-DRB1 13 and birch allergy is identified.

Do allergic families avoid keeping furry pets?

Studies addressing the relationship between pet keeping and development of asthma and allergies may be influenced by pet avoidance in families with a history of allergic disease. Following a cohort of 1019 children in Oslo till 10 years of age, we studied the association of pet keeping with socio-economic factors and allergic disease in the family. A family history of asthma and rhinoconjunctivitis was not significantly associated with pet ownership at birth or with pet removal by 10 years. Acquiring cats and dogs was less likely if the child had allergic rhinoconjunctivitis, whereas no association was seen with asthma (in any family member). Single parenthood increased the likelihood of acquiring a cat, smoking parents more often had cats or dogs, and having older siblings was associated with keeping dogs and other furry pets. Among 319 families reporting pet avoidance, 70% never had pets, 8% had given up pets, and 22% avoided a particular type of pet only. Twenty-four per cent of the parents failed to retrospectively report pet keeping during the child's first year of life. Overall, allergic rhinitis, but not asthma was associated with actual pet avoidance, whereas the strongest predictors for keeping pets were found to be socio-economic factors.

PRACTICAL IMPLICATIONS

Allergic disease in a child most often does not lead to the removal of the family's furry pet. Pet avoidance is associated with allergic symptoms, but not asthma. Socio-economic factors like parental education, single parenthood and smoking affects the families' decisions on pet keeping, including the type of pets the families will avoid or acquire. The large recall error demonstrated points to the need for prospective data regarding pet keeping.

Asthma prediction in school children; the value of combined IgE-antibodies and obstructive airways disease severity score

BACKGROUND

Allergic sensitisation increases the risk for asthma development. In this prospective birth cohort (Environment and Childhood Asthma) study, we hypothesized that combining quantitative measures of IgE antibodies (Sigma-IgE) and Severity score of obstructive airways disease (OAD) at 2 years of age (Severity score) is superior to predict current asthma (CA) at 10 years than either measure alone. Secondarily, we assessed if gender modified the prediction of CA.

METHODS

A follow-up study at 10 years of age was performed in 371 2-year-old children with recurrent (n = 219) or no (n = 152) bronchial obstruction with available serum analysed for Sigma-IgE to common food and inhalant allergens through a panel test, Phadiatop Infant) (Phadia, Uppsala, Sweden). Clinical variables included allergic sensitisation and exercise testing to characterise children with CA vs not CA at 10 years and the Severity score (0-12, 0 indicating no OAD) was used to assess risk modification.

RESULTS

Severity score alone explained 24% (Nagelkerke R(2) = 0.24) of the variation in CA, whereas Sigma-IgE explained only 6% (R(2) = 0.06). Combining the two increased the explanatory capacity to R(2) = 0.30. Gender interacted significantly with Sigma-IgE; whereas Severity score predicted CA in both genders, the predictive capacity of Sigma-IgE for CA at 10 years was significant in boys only.

CONCLUSION

Combining Sigma-IgE to inhalant allergens and Severity score at 2 years was superior to predict asthma at 10 years than either alone. Severity score predicted CA in both genders, whereas Sigma-IgE significantly predicted CA in boys only.