Increase in pollen sensitization in Swedish adults and protective effect of keeping animals in childhood

BACKGROUND

To date, most studies of the 'allergy epidemic' have been based on self-reported data. There is still limited knowledge on time trends in allergic sensitization, especially among adults.

OBJECTIVE

To study allergic sensitization, its risk factors and time trends in prevalence.

METHODS

Within West Sweden Asthma Study (WSAS), a population-based sample of 788 adults (17-60 years) underwent skin prick tests (SPTs) for 11 aeroallergens 2009-2012. Specific IgE was analysed in 750 of the participants. Those aged 20-46 years (n = 379) were compared with the European Community Respiratory Health Survey sample aged 20-46 year from the same area (n = 591) in 1991-1992.

RESULTS

Among those aged 20-46 years, the prevalence of positive SPT to pollen increased, timothy from 17.1% to 29.0% (P < 0.001) and birch from 15.6% to 23.7% (P = 0.002) between 1991-1992 and 2009-2012. Measurements of specific IgE confirmed these increases. Prevalence of sensitization to all other tested allergens was unchanged. In the full WSAS sample aged 17-60 years, any positive SPT was seen in 41.9%, and the dominating sensitizers were pollen (34.3%), animals (22.8%) and mites (12.6%). Pollen sensitization was strongly associated with rhinitis, whereas indoor allergens were more associated with asthma. Growing up with livestock or furred pets decreased the risk of sensitization, adjusted odds ratio 0.53 (0.28-0.995) and 0.68 (0.47-0.98), respectively.

CONCLUSION

Pollen sensitization has increased in Swedish adults since the early 1990s, while the prevalence of sensitization to other allergens has remained unchanged. This is one plausible explanation for the increase in rhinitis 1990-2008 in Swedish adults, during which time the prevalence of asthma, which is more associated with perennial allergens, was stable. Contact with animals in childhood seems to reduce the risk of sensitization well into adulthood. One major factor contributing to the rise in pollen allergy is a significant increase in levels of birch and grass pollen over the past three decades.

Aspirin-intolerant asthma in the population: prevalence and important determinants

BACKGROUND

Population-based studies on aspirin-intolerant asthma (AIA) are very few, and no previous population study has investigated risk factors for the condition.

OBJECTIVE

To investigate the prevalence and risk factors of AIA in the general population.

METHODS

A questionnaire on respiratory health was mailed to 30,000 randomly selected subjects aged 16-75 years in West Sweden, 29,218 could be traced and 18,087 (62%) responded. The questionnaire included questions on asthma, respiratory symptoms, aspirin-induced dyspnoea and possible determinants.

RESULTS

The prevalence of AIA was 0.5%, 0.3% in men and 0.6% in women (P = 0.014). Sick leave, emergency visits due to asthma and all investigated lower respiratory symptoms were more common in AIA than in aspirin-tolerant asthma (ATA). Obesity was a strong risk factor for AIA (BMI > 35: odds ratio (OR) 12.1; 95% CI 2.49-58.5), and there was a dose-response relationship between increasing body mass index (BMI) and risk of AIA. Obesity, airborne occupational exposure and visible mould at home were considerably stronger risk factors for AIA than for ATA. Current smoking was a risk factor for AIA (OR 2.55; 95% CI 1.47-4.42), but not ATA.

CONCLUSION

Aspirin-intolerant asthma identified in the general population was associated with a high burden of symptoms, uncontrolled disease and a high morbidity. Increasing BMI increased the risk of AIA in a dose-response manner. A number of risk factors, including obesity and current smoking, were considerably stronger for AIA than for ATA.

Decreased importance of environmental risk factors for childhood asthma from 1996 to 2006

BACKGROUND

The large increase in asthma prevalence continues in several, but not all areas. Despite the individual risk factors that have been identified, the reasons for the observed trends in prevalence are largely unknown.

OBJECTIVE

This study sought to characterize what trends in risk factors accompanied trends in asthma prevalence.

METHODS

Two population-based cohorts of 7- to 8-year-old children from the same Swedish study areas examined by expanded International Study of Asthma and Allergy in Childhood questionnaires were compared 10 years apart. In 1996 and 2006, 3430 (97% participation) and 2585 (96% participation) questionnaires were completed, respectively. A subset was skin-prick-tested: in 1996 and 2006, 2148 (88% participation) and 1700 (90% participation) children, respectively. The adjusted population-attributable fraction (aPAF) was calculated using the prevalence and multivariate odds ratio of each risk factor.

RESULTS

The prevalence of current asthma and wheeze was similar in 1996 and 2006. Allergic sensitization, however, increased from 21% to 30%. The prevalence of parental asthma increased from 17% to 24%, while respiratory infections and maternal smoking decreased (60% to 29% and 32% to 16%, respectively). The aPAFs of non-environmental risk factors for current asthma increased in 1996-2006: allergic sensitization from 35% to 41%, parental asthma from 27% to 45% and male sex from 20% to 25%. Conversely, the aPAFs of environmental risk factors decreased: respiratory infections from 36% to 32% and damp home and maternal smoking from 14% and 19%, respectively, to near zero in 2006.

CONCLUSIONS AND CLINICAL RELEVANCE

From 1996 to 2006, the non-environmental risk factors parental asthma, allergic sensitization and male sex had an increasing or constant importance for current asthma in 7- to 8-year-old children. The importance of the environmental exposures damp home, respiratory infections and maternal smoking decreased. This counterbalancing in risk factors may explain the level of prevalence of current asthma.

Gas, dust, and fumes exposure is associated with mite sensitization and with asthma in mite-sensitized adults

Occupational exposure to gas, dust, and fumes (GDF) increases the risk of asthma and eczema. We investigated the role of sensitization in the association between GDF and allergic conditions. A population-based sample of 788 adults from the West Sweden Asthma Study completed questionnaires and skin prick tests. After adjustment for confounders, GDF exposure was associated with a doubled risk of sensitization to mites, but not with other allergens. Mite sensitization also modified the effect of GDF on asthma. In mite-sensitized subjects, GDF was associated with physician-diagnosed asthma, adjusted OR 2.9 (1.2-7.2), and with wheeze, OR 2.4 (1.1-5.3). In non-mite-sensitized subjects, the corresponding ORs were 1.1 (0.5-2.6) and 0.6 (0.3-1.3). GDF was independently associated with eczema regardless of mite sensitization, but not with rhinitis. These novel findings suggest that components of GDF may act as adjuvants that facilitate sensitization to mites and that mite-sensitized individuals may be especially susceptible to inhalant occupational exposures.

International consensus on (ICON) pediatric asthma

Asthma is the most common chronic lower respiratory disease in childhood throughout the world. Several guidelines and/or consensus documents are available to support medical decisions on pediatric asthma. Although there is no doubt that the use of common systematic approaches for management can considerably improve outcomes, dissemination and implementation of these are still major challenges. Consequently, the International Collaboration in Asthma, Allergy and Immunology (iCAALL), recently formed by the EAACI, AAAAI, ACAAI, and WAO, has decided to propose an International Consensus on (ICON) Pediatric Asthma. The purpose of this document is to highlight the key messages that are common to many of the existing guidelines, while critically reviewing and commenting on any differences, thus providing a concise reference. The principles of pediatric asthma management are generally accepted. Overall, the treatment goal is disease control. To achieve this, patients and their parents should be educated to optimally manage the disease, in collaboration with healthcare professionals. Identification and avoidance of triggers is also of significant importance. Assessment and monitoring should be performed regularly to re-evaluate and fine-tune treatment. Pharmacotherapy is the cornerstone of treatment. The optimal use of medication can, in most cases, help patients control symptoms and reduce the risk for future morbidity. The management of exacerbations is a major consideration, independent of chronic treatment. There is a trend toward considering phenotype-specific treatment choices; however, this goal has not yet been achieved.

Eczema among adults: prevalence, risk factors and relation to airway diseases. Results from a large-scale population survey in Sweden

BACKGROUND

In contrast to asthma and rhinitis, few studies among adults investigating the prevalence and risk factors of eczema have been published.

OBJECTIVES

To investigate the prevalence and risk factors of eczema among adults in West Sweden. A further aim was to study the associations between asthma, rhinitis and eczema.

METHODS

A questionnaire on respiratory health was mailed in 2008 to 30,000 randomly selected subjects in West Sweden aged 16-75 years; 62% responded. The questionnaire included questions about eczema, respiratory symptoms and diseases and their possible determinants. A subgroup of 669 subjects underwent skin prick testing against common airborne allergens.

RESULTS

'Eczema ever' was reported by 40·7% and 'current eczema' by 11·5%. Both conditions were significantly more common among women. The prevalence decreased with increasing age. The coexistence of both asthma and rhinitis with eczema was common. The main risk factors were family history of allergy and asthma. The dominant environmental risk factor was occupational exposure to gas, dust or fumes. Smoking increased the risk. Eczema was associated with urbanization, while growing up on a farm was associated with a decreased risk. Added one by one to the multivariate model, asthma, allergic rhinitis and any positive skin prick test were associated with eczema.

CONCLUSIONS

Eczema among adults is a common disease with more women than men having and having had eczema. Eczema is associated with other atopic diseases and with airway symptoms. Hereditary factors and exposure to gas, dust and fumes are associated with eczema.

Multi-symptom asthma as an indication of disease severity in epidemiology

Epidemiological questionnaires have failed to identify individuals with severe asthma. The extent of symptoms of asthma can, however, be easily established in epidemiology, by identification of multiple symptoms. We hypothesise that reporting of multiple symptoms of asthma reflects uncontrolled disease and is a sign of more severe asthma. The aims of the current study were, therefore, to determine the prevalence and determinants of multi-symptom asthma. A postal questionnaire was sent to 30,000 randomly selected individuals aged 16-75 yrs. A subgroup underwent clinical examinations. Multi-symptom asthma was defined as reported physician-diagnosed asthma, use of asthma medication, recurrent wheeze, attacks of shortness of breath and at least one additional respiratory symptom. The prevalence of multi-symptom asthma was 2.0%, and it was more common among females (2.4 versus 1.5%; p<0.001) and those with a body mass index >30 kg · m(-2). Multi-symptom asthmatics had lower forced expiratory volume in 1 s, higher exhaled nitric oxide fraction and more pronounced hyperresponsiveness. Family history of both asthma and allergy (OR 7.3), and occupational exposure to gas dust or fumes (OR 2.0) were also significant risk factors. Multi-symptom asthmatics comprise 2% of the general population; multi-symptom asthma is related to signs of more severe disease and could be used as an epidemiological marker of disease severity.

Bed-sharing among six-month-old infants in western Sweden

AIM

In spite of several reports of an increased risk of sudden infant death syndrome (SIDS) in connection with bed-sharing, it is not an uncommon practice. The aim of this study was to examine bed-sharing at 6 months of age and the factors that are associated with bed-sharing.

METHODS

Our cohort comprised 8176 randomly chosen families. At 6 month of age, the families received an invitation to the study, with a questionnaire, which was completed by 5605 families (response rate 68.5%).

RESULTS

Of the families, 19.8% bed-shared. In the multivariate analysis, we found a correlation between breast-feeding and bed-sharing (breast-feeding at 6 months: OR 1.94; 95% CI 1.56, 2.41). Moreover, we found an association with 3+ nightly awakenings at 6 months (2.70; 2.20, 3.32). It was more common to share a bed if the parent was single (2.04; 1.19, 3.51) and less common if the infant was bottle-fed in the first week (0.70; 0.54, 0.90). Never using a pacifier was associated with a higher frequency of bed-sharing.

CONCLUSION

We found a correlation between breast-feeding and bed-sharing as well as between sleeping problems and a single parent. A lower percentage of infants sleeping in the parental bed were seen in association with formula feeding in the first week after birth.

Growing up on a farm leads to lifelong protection against allergic rhinitis

BACKGROUND

Various studies have reported a low prevalence of allergic rhinitis in farmers and farmers' children. We sought to investigate whether the protective effect of childhood farm environment is conserved throughout adulthood and how it corresponds to different degrees of urbanization.

METHODS

A questionnaire on respiratory health was mailed in 2008 to 30,000 randomly selected subjects aged 16-75 in West Sweden, 29,218 could be traced and 18,087 (62%) responded. The questionnaire included questions on allergic rhinitis, asthma, respiratory symptoms and possible determinants.

RESULTS

When stratified into age groups of 15 years, subjects that lived on a farm during their first 5 years of life had a lower prevalence of allergic rhinitis in all groups, even among the oldest (61-75 years). The negative correlation between childhood farm living and prevalence of allergic rhinitis was similar in 46-75 years of age (OR 0.82; 95% CI 0.70-0.95) as in 16-45 years of age (OR 0.78; 0.64-0.95). There was a significant trend of increasing prevalence of allergic rhinitis with increasing degree of urbanization independent of the effect of childhood farm living.

CONCLUSIONS

We found a lifelong protective effect of childhood farm living on the prevalence of allergic rhinitis. In addition, we found an increasing prevalence of allergic rhinitis with increasing degree of urbanization both in those raised on a farm and those not, thus emphasizing the influence of both childhood and adult exposure for the development of allergic disease.

Assessment of problematic severe asthma in children

Assessment of problematic severe asthma in children should be performed in a step-wise manner to ensure an optimal approach. A four-step assessment scheme is proposed. First, a full diagnostic work-up is performed to exclude other diseases which mimic asthma. Secondly, a multi-disciplinary assessment is performed to identify issues that may need attention, including comorbidities. Thirdly, the pattern of inflammation is assessed, and finally steroid responsiveness is documented. Based upon these four steps an optimal individualised treatment plan is developed. In this article the many gaps in our current knowledge in all these steps are highlighted, and recommendations for current clinical practice and future research are made. The lack of good data and the heterogeneity of problematic severe asthma still limit our ability to optimise the management on an individual basis in this small, but challenging group of patients.

Problematic severe asthma in children, not one problem but many: a GA2LEN initiative

Although most children with asthma are easy to treat with low doses of safe medications, many remain symptomatic despite every therapeutic effort. The nomenclature regarding this group is confusing, and studies are difficult to compare due to the proliferation of terms describing poorly defined clinical entities. In this review of severe asthma in children, the term problematic severe asthma is used to describe children with any combination of chronic symptoms, acute severe exacerbations and persistent airflow limitation despite the prescription of multiple therapies. The approach to problematic severe asthma may vary with the age of the child, but, in general, three steps need to be taken in order to separate difficult-to-treat from severe therapy-resistant asthma. First, confirmation that the problem is really due to asthma requires a complete diagnostic re-evaluation. Secondly, the paediatrician needs to systematically exclude comorbidity, as well as personal or family psychosocial disorders. The third step is to re-evaluate medication adherence, inhaler technique and the child's environment. There is a clear need for a common international approach, since there is currently no uniform agreement regarding how best to approach children with problematic severe asthma. An essential first step is proper attention to basic care.

Increased prevalence of otitis media following respiratory syncytial virus infection

AIM

The aim of this study was to analyse whether, during the 18 months following a respiratory syncytial virus (RSV) infection in infants, there were differences in the prevalence of common infections such as acute otitis media (AOM), compared with controls. We also wanted to see whether passive smoking could be a contributory factor.

METHODS

In a longitudinal study, 33 children who attended the emergency room with an RSV infection (age < or = 7 months) were compared with 37 age-matched controls recruited from routine infant check-ups. The 18-month follow-up consisted of a questionnaire focusing on environmental factors and the child's health during the last 12 months. An allergy skin prick test (SPT) was performed and venous blood was obtained.

RESULTS

The prevalence of AOM and the use of antibiotics were higher in the RSV group than in the controls (p = 0.009 and p = 0.027 respectively). The number of AOMs and the use of antibiotics correlated, r = 0.8. In the RSV group, one or both parents smoked in 52% compared with 14% in the controls (p < 0.001). There were no differences in allergy SPT results.

CONCLUSION

The infants with RSV infection had AOM and were prescribed antibiotics more frequently during the follow-up period. Furthermore, smoking was far more common among the parents of the RSV group. We speculate that passive smoking could be a contributory factor to the infections noted here.

Low levels of exhaled nitric oxide are associated with impaired lung function in cystic fibrosis

Fraction of exhaled nitric oxide (FENO) is often reduced in cystic fibrosis (CF). FENO at different expiratory flows can provide an indication of the site of nitric oxide production. The aim of this study was to examine whether NO parameters are related to overall (FEV(1)) or peripheral (lung clearance index, LCI, measured by multiple breath SF(6) washout) airway function and systemic inflammation in CF. Secondary aim was to compare alveolar NO and bronchial NO flux calculated by two different mathematical models, a linear and a nonlinear method. Thirty-five healthy and 45 CF children were recruited. FENO at 50 ml/sec (FENO(50)) and bronchial NO flux were lower in CF than controls, 9.5 (2.7-38.8) (median (range)) versus 12.4 (5.2-40.1) ppb, P = 0.029, and 391 (97-1772) versus 578 (123-1993) (pl/sec), P = 0.036, respectively. No difference in alveolar NO was shown. The nonlinear method resulted in lower alveolar NO and higher bronchial flux, than the linear method, but the result was closely correlated in both groups. LCI was higher in CF than controls, 8.4 (6.5-12.9) versus 5.9 (5.1-7.8), P < 0.001. FENO(50) was negatively correlated with LCI (r = -0.43; P = 0.003) and positively correlated with FEV(1) (r = 0.42, P = 0.004) in CF. Alveolar NO correlated negatively with inflammatory markers: orosomucoid (r = -0.42, P = 0.005), platelets (r = -0.50, P < 0.001) and white blood cell count (r = -0.48, P = 0.001). In conclusion, FENO(50) and bronchial NO flux are reduced in young CF subjects and low FENO(50) is associated with overall and small airway obstruction. NO parameters derived from the different models were closely related but the values differed slightly.

Definition, assessment and treatment of wheezing disorders in preschool children: an evidence-based approach

There is poor agreement on definitions of different phenotypes of preschool wheezing disorders. The present Task Force proposes to use the terms episodic (viral) wheeze to describe children who wheeze intermittently and are well between episodes, and multiple-trigger wheeze for children who wheeze both during and outside discrete episodes. Investigations are only needed when in doubt about the diagnosis. Based on the limited evidence available, inhaled short-acting beta(2)-agonists by metered-dose inhaler/spacer combination are recommended for symptomatic relief. Educating parents regarding causative factors and treatment is useful. Exposure to tobacco smoke should be avoided; allergen avoidance may be considered when sensitisation has been established. Maintenance treatment with inhaled corticosteroids is recommended for multiple-trigger wheeze; benefits are often small. Montelukast is recommended for the treatment of episodic (viral) wheeze and can be started when symptoms of a viral cold develop. Given the large overlap in phenotypes, and the fact that patients can move from one phenotype to another, inhaled corticosteroids and montelukast may be considered on a trial basis in almost any preschool child with recurrent wheeze, but should be discontinued if there is no clear clinical benefit. Large well-designed randomised controlled trials with clear descriptions of patients are needed to improve the present recommendations on the treatment of these common syndromes.

Early introduction of fish decreases the risk of eczema in infants

BACKGROUND

Atopic eczema in infants has increased in western societies. Environmental factors and the introduction of food may affect the risk of eczema.

AIMS

To investigate the prevalence of eczema among infants in western Sweden, describe patterns of food introduction and assess risk factors for eczema at 1 year of age.

METHODS

Data were obtained from a prospective, longitudinal cohort study of infants born in western Sweden in 2003; 8176 families were randomly selected and, 6 months after the infant's birth, were invited to participate and received questionnaires. A second questionnaire was sent out when the infants were 12 months old. Both questionnaires were completed and medical birth register data were obtained for 4921 infants (60.2% of the selected population).

RESULTS

At 1 year of age, 20.9% of the infants had previous or current eczema. Median age at onset was 4 months. In multivariable analysis, familial occurrence of eczema, especially in siblings (OR 1.87; 95% confidence interval (CI) 1.50 to 2.33) or the mother (OR 1.54; 95% CI 1.30 to 1.84), remained an independent risk factor. Introducing fish before 9 months of age (OR 0.76; 95% CI 0.62 to 0.94) and having a bird in the home (OR 0.35; 95% CI 0.17 to 0.75) were beneficial.

CONCLUSIONS

One in five infants suffer from eczema during the first year of life. Familial eczema increased the risk, while early fish introduction and bird keeping decreased it. Breast feeding and time of milk and egg introduction did not affect the risk.

A real-life cost-effectiveness evaluation of budesonide/formoterol maintenance and reliever therapy in asthma

OBJECTIVE

To evaluate direct asthma-related costs in Swedish primary care in a real-life setting.

DESIGN

12-month open-label study.

SETTING

Swedish primary care in a real-life setting.

PARTICIPANTS

1776 patients with persistent asthma.

INTERVENTIONS

Patients with persistent asthma were randomised to one of three treatments: a free adjustable combination of budesonide (100-400 microg/inhalation) and formoterol (4.5 or 9 microg/inhalation) via separate inhalers plus terbutaline as needed; budesonide/formoterol (160/4.5 microg or 80/4.5 microg, two inhalations twice daily) plus terbutaline as needed; budesonide/formoterol (160/4.5 microg or 80/4.5 microg, one inhalation twice daily or two inhalations once daily), for maintenance plus additional inhalations as needed. Doses depended on previous inhaled corticosteroid dose. Patients attended the clinic at 0, 1.5, and 12 months. Telephone interviews were conducted at 4, 6, 8, and 10 months.

MAIN OUTCOME MEASURES

The primary endpoint was direct asthma-related healthcare costs.

RESULTS

Statistically significant reductions in annual direct costs per patient were observed with budesonide/formoterol maintenance and reliever therapy compared with the free adjustable combination of budesonide and formoterol (-13%, P<0.001) and fixed-dose budesonide/formoterol plus terbutaline (-20%, P<0.001). Time to first severe exacerbation did not differ significantly across treatment groups, with a mean reduction of 28% versus the free adjustable combination of budesonide and formoterol (P=0.076). Patients receiving budesonide/formoterol maintenance and reliever therapy used a significantly lower daily dose of budesonide compared with the conventional (P<0.001).

CONCLUSIONS

This study reports direct cost savings with budesonide/formoterol maintenance and reliever therapy compared with conventional treatment regimens with at least equivalent efficacy.

Determinants of lung function and airway hyperresponsiveness in asthmatic children

BACKGROUND

Asthma patients exhibit an increased rate of loss of lung function. Determinants to such decline are largely unknown and the modifying effect of steroid therapy is disputed. This cross-sectional study aimed to elucidate factors contributing to such decline and the possible modifying effect of steroid treatment.

METHODS

We analyzed determinants of lung function and airway hyperresponsiveness (AHR) in a Scandinavian study of 2390 subjects from 550 families. Families were selected for the presence of two or more asthmatic children as part of a genetic study, Scandinavian Asthma Genetic Study (SAGA).

RESULTS

The primary analysis studied the association between the lung function and delay of inhaled corticosteroids (ICS) after asthma diagnosis among asthmatic children and young adults with a history of regular ICS treatment (N=919). FEV(1) percent predicted (FEV(1)% pred) was 0.25% lower per year of delay from diagnosis until treatment (p=0.039). This association was significantly greater in allergy skin prick test negative children. There was no significant influence of gender, age at asthma onset, or smoking. In the secondary analysis of the whole population of 2390 asthmatics and non-asthmatics, FEV(1)% pred was inversely related to having asthmatic siblings (-7.9%; p<0.0001), asthma diagnosis (-2.7%; p=0.0007), smoking (-3.5%; p=0.0027), and positive allergy skin prick test (-0.47% per test; p=0.012), while positively related to being of female gender (1.8%; p=0.0029). Risk of AHR was higher by having asthmatic siblings (OR 2.7; p<0.0001), being of female gender (OR 2.0; p<0.0001), and having asthma (OR 2.0; p<0.0001).

CONCLUSIONS

These data suggest that lung function is lower in asthmatics with delayed introduction of ICS therapy, smoking, and positive allergy skin prick test. Lung function is lower and AHR higher in female asthmatics and subjects with asthmatic siblings or established asthma.

SIDS risk factors and factors associated with prone sleeping in Sweden

OBJECTIVE

To compare the current prevalence of risk factors for sudden infant death syndrome (SIDS) in Sweden with a decade earlier, and assess factors associated with prone sleeping.

METHODS

The results of a cohort study (Infants of Western Sweden) and a population based case-control study (Nordic Epidemiological SIDS Study) were examined. Subjects were 5600 healthy 6 month old infants born in 2003 in the Western Sweden region and 430 healthy Swedish infants born between 1991 and 1995.

RESULTS

Prone sleeping decreased from 31.8% to 5.6% and supine sleeping increased from 35.3% to 47.3%. Side or side/supine sleeping increased from 25.2% to 43.8%. Maternal smoking during pregnancy decreased from 23.5% to 9.5%. The risk for prone sleeping increased if the mother was unemployed (OR 2.4, 95% CI 1.5 to 4.0), if she was a heavy smoker in the third trimester (OR 44.1, 95% CI 1.6 to 1199.6), and if the child was irritable (OR 2.5, 95% CI 1.3 to 5.1), shared a bedroom with siblings (OR 2.6, 95% CI 1.0 to 6.6), or never used a dummy (OR 3.2, 95% CI 1.9 to 5.4).

CONCLUSIONS

Parents have complied with advice to prevent SIDS given at infant welfare centres for the last 10 years. A change in the preferred sleeping position from side variants to exclusively supine, and reducing the number of pregnant women smoking may be beneficial. Use of a prone sleeping position was associated with maternal employment status, maternal smoking, temperament of the child, dummy use, and sharing a bedroom with siblings.

Low levels of CC16 in nasal fluid of children with birch pollen-induced rhinitis

BACKGROUND

Clara cell protein 16 (CC16; secretoglobin 1A1) is an anti-inflammatory protein mainly expressed in the epithelial cells in the airways.

OBJECTIVE

To compare the levels of CC16 in nasal lavage (NAL) from children with intermittent allergic rhinitis and healthy controls and to study the effect of a local steroid.

METHODS

Thirty schoolchildren with birch pollen allergy and 30 healthy controls from the same schools were included in the study. The NAL fluid was collected before the season, during the birch pollen season and, for the patients, after 1 week of treatment with a local steroid. Symptom scores were obtained on every occasion. CC16 and eosinophil cationic protein (ECP) were analyzed with enzyme-linked immunosorbent assay.

RESULTS

The nasal fluid levels of CC16 were significantly lower in patients than in controls, before and during pollen season. Before the season, the median CC16 concentrations were 9.1 (range 1.1-117) microg/l in patients and 25.7 (6.1-110.2) microg/l in controls. During the season, the median CC16 concentrations in nasal fluid were 12.9 (2.3-89.7) microg/l in the allergic children and 22.0 (9.5-90.1) microg/l in the healthy controls (P = 0.0005). Symptom scores, nasal fluid eosinophils and ECP were higher in patients during the season. Treatment with a local steroid did not change the CC16 levels.

CONCLUSIONS

Nasal fluid CC16 levels were lower in children with birch pollen-induced allergic rhinitis than in healthy controls both before and during the pollen season. We speculate that reduction in anti-inflammatory activity by CC16 may contribute to the pathogenesis of allergic rhinitis.

Outcome of wheezing in early childhood

In Acta Paediatrica 50 y ago, Boesen published a follow-up of children with "asthmatic bronchitis". Recent reinvestigations of children hospitalized because of wheezing in early childhood are remarkably consistent with Boesen's observations.

CONCLUSION

Young children admitted to hospital because of wheezing have a clearly increased risk of subsequent asthma. Recent studies confirm Boesen's observations of the prognostic importance of eosinophilia and an inverse relation between age at admission with wheezing and risk of subsequent asthma. Allergy or atopic dermatitis is predictive of subsequent asthma, whereas family history of allergy has low predictive value in infants.

Circadian variations in sudden infant death syndrome: associations with maternal smoking, sleeping position and infections. The Nordic Epidemiological SIDS Study

AIM

To study circadian variation in the sudden infant death syndrome (SIDS) and possible associations with risk factors for SIDS.

METHODS

A questionnaire-based case-control study matched for place of birth, age and gender was conducted in Denmark, Norway and Sweden: The Nordic Epidemiological SIDS Study. The study comprised 244 SIDS victims and 869 control infants between September 1992 and August 1995. The main outcome was hour found dead.

RESULTS

A significant circadian pattern was observed among the 242 SIDS victims with a known hour found dead, with a peak at 08.00-08.59 in the morning (n = 33). Of the SIDS victims, 12% were found dead at 00.00-05.59, 58% at 06.00-11.59, 21% at 12.00-17.59 and 9.0% at 18.00-23.59. When comparing night/morning SIDS and day/evening SIDS (found dead 00.00-11.59 and 12.00-23.59, respectively), the proportion of night/morning SIDS was high among infants of smoking mothers (81% vs 53%, p < 0.001), infants with a reported cold (82% vs 64%, p = 0.007) and infants sleeping side/supine (81% vs 60%, p < 0.001). No associations were observed between hour found dead and other sociodemographic risk factors for SIDS. Risk (odds ratio and 95% confidence interval) of night/morning SIDS and day/evening SIDS was 7.0 (4.5-10.9) and 1.5 (0.8-2.5), respectively, for maternal smoking, 2.2 (1.5-3.1) and 0.6 (0.3-1.3), respectively, if the infant had a reported cold, 3.7 (2.1-6.6) and 3.1 (1.1-8.4), respectively, if the infant was put to sleep in the side position (supine reference), and 11.0 (5.9-20.2) and 21.6 (7.6-60.8), respectively, if the infant was put to sleep in the prone position.

CONCLUSION

The observed higher proportion of night/morning cases in SIDS if the mother smoked, if the infant was reported to have a cold and if the infant was sleeping side/supine may contribute to the understanding of some epidemiological characteristics of SIDS.

Vitamin A and sudden infant death syndrome in Scandinavia 1992-1995

AIM

To assess the effect of vitamin supplementation on the risk of sudden infant death syndrome (SIDS).

METHODS

The analyses are based on data from the Nordic Epidemiological SIDS Study, a case-control study in which parents of SIDS victims in the Scandinavian countries were invited to participate together with parents of four matched controls between 1 September 1992 and 31 August 1995. The odds ratios presented are computed by conditional logistic regression analysis.

RESULTS

The crude odds ratio in Scandinavia for not giving vitamin substitution was 2.8 (95% CI (1.9, 4.3)). This effect was statistically significant in Norway and Sweden, which use A and D vitamin supplementation, but not in Denmark, where only vitamin D supplementation is given. The odds ratios remained significant in Sweden when an adjustment was made for confounding factors (OR 28.4, 95% CI (4.7, 171.3)).

CONCLUSION

We found an association between increased risk of sudden infant death syndrome and infants not being given vitamin supplementation during their first year of life. This was highly significant in Sweden, and the effect is possibly connected with vitamin A deficiency. This effect persisted when an adjustment was made for potential confounders, includingsocioeconomic factors.

Asthma hospitalizations continue to decrease in schoolchildren but hospitalization rates for wheezing illnesses remain high in young children

AIM

To analyse changes in hospitalization rates for asthma in children during recent years.

METHODS

In a population-based analysis, changes in asthma hospitalization rates were studied in children in Göteborg (Gothenburg), the second largest city in Sweden, during 1985-2000. The changes in different age groups have been correlated with the delivery of inhaled corticosteroids to the age groups.

RESULTS

In the 5 to 18-y age group, there was a continuous, significant decrease in number of hospital days, admissions and individual patients admitted for asthma not only for the entire study period, 1985-2000, but also during the past 10-y period. The number of hospital days in the year 2000 was only 6% of the figure for 1985. An inverse correlation between delivery of inhaled corticosteroids and hospitalization for asthma was seen not only during 1985-1995, when use of inhaled corticosteroids became widespread (r(s) = -0.95, p = 0.007 for hospital days), but also when the entire period from 1985 to 2000 was analysed. Conversely, in the 0 to 1-y and 2 to 4-y age groups, there was no decrease in hospitalizations for wheezing illnesses or asthma-like symptoms during the past 10-y period, 1991-2000.

CONCLUSION

During the period 1985-2000 the number of hospital days owing to asthma decreased by more than 90% in the 5 to 18-y age group. The marked decrease in asthma hospitalization rates among schoolchildren represents a great advance in paediatric respiratory medicine, which has been continuous during the past 10-y period. However, in young children admissions for wheezing have apparently not decreased.

Born small for gestational age: relation to future allergy and asthma

AIM

To evaluate whether intrauterine growth retardation (IUGR) protects against the development of allergy.

METHODS

A case-control study of 1515 subjects (15-25 y), of whom 430 were cases (birthweight/length below -2 SD for gestational age). Birth data were from the national birth register. The frequencies of allergic diseases were evaluated by questionnaire.

RESULTS

For the 950 who replied, the frequencies of allergic diseases were similar in cases and controls.

CONCLUSION

IUGR does not protect against the development of allergy.

Bradycardic response during submersion in infant swimming

The diving response involves reflex bradycardia, apnoea and peripheral vasoconstriction and is known to exist in human infants. The response diminishes with increasing age and has been reported to disappear by the age of 6 mo. This study was performed to analyse the physiological events during natural diving of full-term healthy infants and describe how these events alter with maturation. Thirty-six infants were studied during diving exercises in infant swimming. All of the infants who participated showed an immediate decrease in heart rate when submerged. On average, the heart rate decreased by 25% (range -5.0% to -50.7%, p <0.0001). The bradycardia was sustained during the dive and for some seconds afterwards. The response was often followed by a tachycardia as the bradycardia ceased. A decline of reflex bradycardia was observed with increasing age (p = 0.03), but the response was still clearly evident in infants over the age of 6 mo.

CONCLUSION

This study demonstrates the existence of a diving response in infants, which includes an immediate bradycardic response, suggesting vagal mediation. Although the bradycardic response gradually decreases, the study shows that a clear-cut response exists in children older than has previously been reported.

Breast feeding and the sudden infant death syndrome in Scandinavia, 1992-95

AIMS

To assess the effects of breast feeding habits on sudden infant death syndrome (SIDS).

METHODS

The analyses are based on data from the Nordic Epidemiological SIDS Study, a case-control study in which parents of SIDS victims in the Scandinavian countries between 1 September 1992 and 31 August 1995 were invited to participate, each with parents of four matched controls. The odds ratios presented were computed by conditional logistic regression analysis.

RESULTS

After adjustment for smoking during pregnancy, paternal employment, sleeping position, and age of the infant, the adjusted odds ratio (95% CI) was 5.1 (2.3 to 11.2) if the infant was exclusively breast fed for less than four weeks, 3.7 (1.6 to 8.4) for 4-7 weeks, 1.6 (0.7 to 3.6) for 8-11 weeks, and 2.8 (1.2 to 6.8) for 12-15 weeks, with exclusive breast feeding over 16 weeks as the reference. Mixed feeding in the first week post partum did not increase the risk.

CONCLUSIONS

The study is supportive of a weak relation between breast feeding and SIDS reduction.

Relationship between respiratory syncytial virus bronchiolitis and future obstructive airway diseases

Evidence from a large number of prospective case-control studies shows that respiratory syncytial virus (RSV) bronchiolitis in infancy is often associated with recurrent wheezing and asthma during subsequent years. However, wheezing tends to diminish and most studies show no significant increase in wheezing compared to controls by school age or adolescence. An unresolved question is whether severe RSV infection during infancy causes the respiratory sequelae or inherent abnormalities predispose an infant to develop severe respiratory infection and sequelae, i.e. RSV is associated with the development of pulmonary sequelae. Studies on long-term outcome of RSV bronchiolitis are reviewed from an evidence-based perspective. The majority of prospective placebo-controlled studies do not show any long-term beneficial effects of corticosteroid treatment, i.e. the risk of subsequent wheezing is not diminished by the treatment. The evidence for an increased risk of allergic sensitization after RSV bronchiolitis is not nearly as strong as the evidence for an increased risk of subsequent wheezing. In fact, most studies do not show any significant increase in atopy after RSV bronchiolitis. This suggests that the increased risk of wheezing after RSV is not linked to an increased risk of atopy. There are some indications that infants who develop severe RSV and subsequent wheezing may have aberrations that predate the RSV infection. To decide whether respiratory syncytial virus bronchiolitis causes, or is associated with the respiratory sequelae (or with subsequent allergy), it will be necessary to conduct prospective, randomized studies, where the cytokine profile prior to bronchiolitis onset is known. Such studies should preferably include some form of intervention against respiratory syncytial virus. A more complete understanding of the risk factors for severe respiratory syncytial virus infection and the role of respiratory syncytial virus infection in the initiation of asthma is needed as a basis for large-scale and cost-effective programmes to prevent respiratory syncytial virus-related morbidity.

Changes in the epidemiology of sudden infant death syndrome in Sweden 1973-1996

BACKGROUND

From the early 1970s to the early 1990s, there was a significant rise in the incidence of sudden infant death syndrome (SIDS) in Scandinavia. Following the risk reducing campaign, the incidence has fallen to about the same level as in 1973.

AIMS

To identify the changes that have occurred in the epidemiology of SIDS.

METHODS

We compared the Swedish part of the Nordic Epidemiological SIDS Study (NESS), covering the years 1992-1995, with two earlier, descriptive studies during this period. To assess the changing effects of risk factors, we analysed data from the Medical Birth Registry of Sweden, covering the years 1973-1996.

RESULTS

There was a predominance of deaths during weekends in the 1970s and 1990s. The seasonal variation was most notable in the 1980s. The proportion of young mothers decreased from 14% to 5%. Cohabitation (living with the biological father) was as frequent in the 1990s as in the 1970s. The prevalence of high parity, admissions to neonatal wards, low birth weight, prematurity, and multiple pregnancies were all increased in the 1990s compared to the 1970s. No significant change in the prevalence of previous apparent life threatening events was found. Deaths occurring in cars diminished from 10% to below 2%. In the data from the Medical Birth Registry of Sweden, there were significantly increased odds ratios after the risk reducing campaign of the risk factors smoking during early pregnancy and preterm birth. We could find no increased effects of maternal age, parity, or being small for gestational age over time. The rate of deaths at weekends remained increased; the median age at death fell from 90 to 60 days. Seasonal variation was less notable in the periods of low incidence.

Inflammatory mediators in blood and urine

Inflammation plays a major role in the pathophysiology of asthma. Therefore, monitoring of the disease and its management preferably should include assessment of mediators of airways inflammation. Much interest has been focused on using eosinophil granule proteins in blood and urine as markers of asthma inflammation. The eosinophil granule proteins are important mediators in allergic inflammation. They often function well as inflammatory markers when used in controlled clinical studies, and are therefore useful research tools. With urinary eosinophil-derived protein X (EPX) venous blood sampling is avoided. Disadvantages which limit usefulness in clinical practice are overlap between values in patients and controls, a rather weak correlation to traditional lung function variables, elevation of levels by concurrent allergic disease, and the delay between sampling and test results. Urinary excretion of leukotriene E4 (LTE(4)) reflects the production of cysteinyl leukotrienes, which are major mediators in asthma. The excretion of LTE4 possibly reflects lung function better than serum ECP. In the future, monitoring of cytokines may be used in clinical asthma to monitor control and aid in the prognosis of the disease in the young child. Techniques for simple and rapid monitoring of key type 1 and type 2 cytokines are needed.

Topical steroid treatment of allergic rhinitis decreases nasal fluid TH2 cytokines, eosinophils, eosinophil cationic protein, and IgE but has no significant effect on IFN-gamma, IL-1beta, TNF-alpha, or neutrophils

BACKGROUND

Topical treatment with glucocorticoids (GCs) is known to decrease eosinophils but not neutrophils in patients with allergic rhinitis.

OBJECTIVE

We sought to examine whether the differential effects of GC treatment on eosinophils and neutrophils are mirrored by differential effects on T(H)1/T(H)2 cytokines and the neutrophil-associated cytokines IL-1beta and TNF-alpha.

METHODS

Differential counts of eosinophils and neutrophils in nasal fluids from 60 children with seasonal allergic rhinitis treated with a topical GC were examined after staining with May-Grünwald-Giemsa stain. Nasal fluid levels of IFN-gamma, IL-4, IL-6, IL-10, IL-1beta, and TNF-alpha were examined with ELISA, and IgE and eosinophil cationic protein (ECP) levels were examined with RIA.

RESULTS

After GC treatment, there was a statistically significant decrease of the T(H)2 cytokines IL-4, IL-6, and IL-10, as well as ECP and IgE. By contrast, there were no significant changes of the levels of IFN-gamma, IL-1beta, TNF-alpha, or neutrophils. In the GC-treated patients IL-1beta and TNF-alpha levels correlated with neutrophils and ECP, and IL-1beta correlated with eosinophils. Furthermore, ECP correlated with both eosinophils and neutrophils. Neither IL-1beta nor TNF-alpha correlated with IgE. Patients with high neutrophil counts after GC treatment were found to have significantly higher eosinophil counts and ECP than patients with low counts.

CONCLUSIONS

The beneficial effects of topical treatment with GC in patients with allergic rhinitis could be attributed to downregulation of T(H)2 cytokines, with an ensuing decrease of eosinophils, ECP, and IgE. It is possible that neutrophils could counteract the beneficial effects of GCs by releasing the proinflammatory cytokines IL-1beta and TNF-alpha.

Increase of the soluble IL-4 receptor (IL-4sR) and positive correlation between IL-4sR and IgE in nasal fluids from school children with allergic rhinitis

Soluble cytokine receptors (SCR) can either act as inhibitors, by competitively inhibiting cytokines from binding to their membrane-bound receptors, or as enhancers, by serving as cytokine carriers. We have previously found that the levels of the Th2 cytokines interleukin (IL)-4, IL-5, IL-6, and IL-10 were positively correlated to eosinophils and IgE in nasal fluids from 60 children with seasonal allergic rhinitis. In this study, nasal fluids were reexamined to analyze IL-4sR, IL-6sR, IL-1 beta, TNF-alpha, IL-1sR2, TNF-sR1, and TNFsR2 in relation to eosinophils, neutrophils, ECP, and IgE. In allergic patients IL-4sR increased significantly during the pollen season, and weak, but positive correlations with IgE and eosinophils were found (r = 0.45, P < 0.001 and r = 0.4, P < 0.001 respectively). By contrast, none of the other SCR showed increases or correlations with IgE. However, positive correlations between IL1 beta, TNF-alpha, IL-6sR, IL-1sR2, TNF-sR1, TNF-sR2, and either neutrophils or ECP were found. Also, in healthy controls, these cytokines and their receptors were positively correlated to neutrophils or ECP. Thus, increased levels of the soluble IL-4 receptor, as well as IgE, were specifically associated with allergic rhinitis, whereas all other SCR correlated with either inflammatory cells or their products, in both allergic and healthy subjects. These results may suggest that SCR in vivo act as cytokine enhancers, rather than inhibitors.

Low levels of interferon-gamma in nasal fluid accompany raised levels of T-helper 2 cytokines in children with ongoing allergic rhinitis

The T-helper 2 (Th2) cytokines interleukin-(IL-) 4, IL-5, IL-6, IL-10 and the Th1 cytokine IFN-gamma and their associations with eosinophil, eosinophil cationic protein (ECP) and immunoglobulin (Ig) E were studied in nasal lavage fluid from 60 school children with allergic seasonal rhinitis and 36 nonatopic healthy controls, before and during the pollen season. Eosinophil differential counts and IgE increased significantly in the patients during the pollen season. The eosinophil differential counts, ECP and IgE were all significantly higher during the season than in specimens simultaneously obtained from the nonatopic controls. Before season, the levels of ECP and IgE, but not eosinophils, were significantly higher in the patients than in the controls. During the season the nasal lavage fluid levels of IFN-gamma were significantly lower and the IL-4/IFN-gamma quotients significantly higher in the allergic than in the control children. In the allergic children, but not in the controls, the nasal fluid levels of the Th2 cytokines IL-4, IL-5 and IL-10 increased during the season, and together with IL-6, were correlated with the differential counts of eosinophils, and with the levels of ECP and IgE. These findings are compatible with the hypothesis that a deficient release of the Th1 cytokine IFN-gamma plays an important role in the pathogenesis of allergic inflammation. Regardless of whether the defective IFN-gamma secretion is primary or a consequence of suppression by other cytokines, it will in the atopic subjects enhance the release of Th2 cytokines, which in turn will facilitate the development of allergic inflammation.

Living conditions in early infancy in Denmark, Norway and Sweden 1992-95: results from the Nordic Epidemiological SIDS study

The objective was to study living conditions of infants and their families in Scandinavia in the 1990s and to assess similarities and differences among the three Scandinavian countries. The emphasis is on health and normality rather than on diseases and other deviations from well-being. The subjects are the 869 controls in the Nordic Epidemiological SIDS study carried out between 1 September 1992 and 31 August 1995 in Norway, Denmark and Sweden. The controls were matched with the 244 SIDS cases for sex, age and maternity hospital. Parents of the SIDS cases and the controls filled in the same questionnaire on family, pregnancy, delivery, the neonatal and the post-perinatal period. The most striking findings were that 99% of the mothers went to regular maternity controls, 97% to well-baby clinics and 84% breastfed exclusively. On the other hand, 11% drank alcohol more than once a month during pregnancy and 29% smoked during pregnancy. Compared to official statistics, to the extent they exist, the differences were small. The material contains valuable information on normal infant care in Scandinavia in the 1990s. Living conditions of infants in Scandinavia are similar in the three countries. Differences exist, but only to a small extent.

Caffeine and alcohol as risk factors for sudden infant death syndrome. Nordic Epidemiological SIDS Study

OBJECTIVE

To assess whether alcohol and caffeine are independent risk factors for sudden infant death syndrome (SIDS).

MATERIALS AND METHODS

Analyses based on data from the Nordic epidemiological SIDS study, a case control study in which all parents of SIDS victims in the Nordic countries from 1 September 1992 to 31 August 1995 were invited to participate with parents of four controls, matched for sex and age at death. Odds ratios (ORs) were calculated by conditional logistic regression analysis.

RESULTS

The crude ORs for caffeine consumption > 800 mg/24 hours both during and after pregnancy were significantly raised: 3.9 (95% confidence interval (CI), 1.9 to 8.1) and 3.1 (95% CI, 1.5 to 6.3), respectively. However, after adjustment for maternal smoking in 1st trimester, maternal age, education and parity, no significant effect of caffeine during or after pregnancy remained. For maternal or paternal alcohol use, no significant risk increase was found after adjusting for social variables, except for heavy postnatal intake of alcohol by the mother, where the risk was significantly increased.

CONCLUSIONS

Caffeine during or after pregnancy was not found to be an independent risk factor for SIDS after adjustment for maternal age, education, parity, and smoking during pregnancy. Heavy postnatal but not prenatal intake of alcohol by the mother increased the risk.

Interleukin-5 and interleukin-8 in relation to eosinophils and neutrophils in nasal fluids from school children with seasonal allergic rhinitis

The objectives of this study were to measure interleukins 5 and 8 (IL-5 and IL-8) in relation to eosinophils and neutrophils, in nasal lavage fluids from 60 school children with allergic rhinitis, and to determine the influence of treatment with a topical steroid (budesonide) on the levels of the two cytokines. Highly sensitive enzyme immunoassays were used to analyze IL-5 and IL-8. IL-5 levels and relative eosinophil counts in nasal lavage fluid increased significantly in patients with allergic rhinitis during the pollen season, compared with values obtained before the start of the season, and decreased significantly after treatment with budesonide. By contrast, no significant changes in IL-8 or neutrophils were found during the pollen season, nor did they decrease following treatment. In the untreated patients, IL-5 levels correlated significantly with eosinophil counts but not with neutrophil counts, whereas IL-8 levels correlated with neutrophil counts but not with eosinophil counts. After budesonide treatment, the correlation between IL-8 and neutrophils remained, and a correlation between IL-8 and eosinophils emerged. These findings support the concepts that IL-5 has a key role in regulating eosinophils and that IL-8 is important for the regulation of neutrophils. Whereas IL-5 and relative eosinophil counts are profoundly affected by topical steroid treatment, IL-8 and neutrophils are not demonstrably affected by such treatment. It is possible that neutrophils, through the release of IL-8, could be chemotactic for eosinophils in steroid-treated patients.

Interactions of infectious symptoms and modifiable risk factors in sudden infant death syndrome. The Nordic Epidemiological SIDS study

The aim of the study was to investigate the effect of infection on sudden infant death syndrome (SIDS) and to analyse whether modifiable risk factors of SIDS, prone sleeping, covered head and smoking act as effect modifiers. In a consecutive multicentre case-control study of SIDS in Denmark, Norway and Sweden, questionnaires on potential risk factors for SIDS were completed by parents of SIDS victims, and for at least two controls matched for gender, age and place of birth. All SIDS cases were verified by an autopsy. The study comprised 244 SIDS cases and 869 controls, analysed by conditional logistic regression. Significantly more cases than controls presenting symptoms of infectious diseases during the last week and/or last day were treated with antibiotics and had been seen by a physician. The finding is consistent with the hypothesis of an infectious mechanism in SIDS induced by local microorganism growth and toxin or cytokine production, and also adds further support to a possible association between infection and SIDS by loss of protective mechanisms, such as arousal. The risk of SIDS among infants with the combined presence of infectious symptoms and either of the other modifiable risk factors, prone sleeping, head covered or parental smoking, was far greater than the sum of each individual factor. These risk factors thus modify the dangerousness of infection in infancy.

Histamine provocation in young, awake children with bronchial asthma, using a fall in oxygenation as the only indicator of a bronchial reaction

Bronchial provocation with histamine was performed in 11 boys and 6 girls, age range 2.7-7.4 y, with unspecific respiratory symptoms or bronchial asthma, using a fall in oxygenation as the only indicator of a bronchial reaction. In addition to transcutaneous oxygen tension (tcPO2), transcutaneous carbon dioxide tension (tcPCO2) was continuously monitored during the provocation procedure in order to identify possible changes in ventilation. A fall of 20% or more in the tcPO2 below a "floating" baseline value, defined as the highest tcPO2 value between the inhalations of histamine up to that point, was regarded as indicating a significant bronchial reaction. One child was excluded from the study because of an "early, false-positive" reaction due to hyperventilation during the inhalation, verified by a decrease in the tcPCO2 followed by a compensatory period of hypoventilation, resulting in a fall of more than 15% in the tcPO2 after the inhalation of saline. In the vast majority of the children, however, the tcPO2 values remained stable during the first dose stages of saline and histamine, with either a gradual fall immediately before or a distinct fall in conjunction with the reaction. The mean reaction concentration was significantly lower in the group of children with clinical asthma, 0.74 mg/ml, compared with the group of children with unspecific respiratory symptoms, 2.00 mg/ml (p = 0.03). In conclusion, a 20% fall in the tcPO2 can be used as the only indicator of a bronchial reaction during bronchial provocation tests in young, awake children. Changes in ventilation evaluated by monitoring tcPCO2, makes it possible to distinguish between a fall in oxygen tension due to an early, "false" reaction as a result of hypoventilation and a "true" bronchial reaction.

Short- and long-term efficacy. Childhood asthma

In clinical studies of asthma, great attention should be focused on the choice and validation of outcome measures. The outcome parameters to be used when evaluating efficacy of early intervention in childhood asthma treatment must be closely linked to the aims of the intervention and considered in the design of the study. In an interventional study, possible adverse consequences should also be considered as outcome measures when designing the study. The appropriate time span for assessing different types of interventions may vary from days to several decades, depending on the character of the intervention. Not only outcome parameters, such as improvement in symptom score and improvement of lung function, but also those that measure reduction in frequency and severity of acute exacerbations, reduction in morbidity and improvement in quality of life should be used. For some purposes, a more detailed approach to symptom severity is needed, such as separation of acute from chronic symptoms. Other outcome measures that need to be considered are: cost-effectiveness, normalization of inflammatory changes in the airways, control of airway hyperresponsiveness, airway growth and prevention of airway remodelling and importantly, whether an intervention against asthma can alter the natural course, or cure, the disease. Interventions should be evaluated to see to what extent such aims have been met.

A case-control study of smoking and sudden infant death syndrome in the Scandinavian countries, 1992 to 1995. The Nordic Epidemiological SIDS Study

AIM

To establish whether smoking is an independent risk factor for sudden infant death syndrome (SIDS), if the effect is mainly due to prenatal or postnatal smoking, and the effect of smoking cessation.

METHODS

The analyses were based on data from the Nordic epidemiological SIDS study, a case-control study with 244 cases and 869 controls. Odds ratios were computed by conditional logistic regression analysis.

RESULTS

Smoking emerged as an independent risk factor for SIDS, and the effect was mainly mediated through maternal smoking in pregnancy (crude odds ratio 4.0 (95% confidence interval 2.9 to 5.6)). Maternal smoking showed a marked dose-response relation. There was no effect of paternal smoking if the mother did not smoke. Stopping or even reducing smoking was beneficial. SIDS cases exposed to tobacco smoke were breast fed for a shorter time than non-exposed cases, and feeding difficulties were also more common.

CONCLUSIONS

Smoking is an independent risk factor for SIDS and is mainly mediated through maternal smoking during pregnancy. Stopping smoking or smoking less may be beneficial in reducing the risk of SIDS.

Prevalence of allergy in children in relation to prior BCG vaccination and infection with atypical mycobacteria

By influence on the Th1/Th2 cell balance, infectious agents may affect the development of atopic allergy. In this study, we investigated whether previous BCG vaccination or infection with atypical mycobacteria might be related to the development of atopic disease. The study, which involved skin testing with mycobacteria and answers to a questionnaire for more than 6000 children in Sweden, revealed a low prevalence of allergy among BCG-vaccinated children who were immigrants or adopted from other countries. Vaccinated children born in Sweden, however, did not have significantly lower allergy prevalence than age-matched, unvaccinated children. Furthermore, the overall frequencies of skin-test reactivity to the atypical mycobacteria M. avium and M. scrofulaceum were higher rather than lower in allergic than in nonallergic children. By contrast, there was a tendency toward a lower frequency of more strongly positive skin reactions (> or = 10 mm) to mycobacteria in allergic than in nonallergic children. These findings do not support the hypothesis that early mycobacterial infections have a suppressive effect on the development of atopic disease. Earlier findings of an apparent association between atopy and lack of previous mycobacterial infection may possibly be explained by a relatively decreased ability of atopic patients to mount strong Th1 cell-mediated immune responses.

Sociodemographic risk factors for sudden infant death syndrome: associations with other risk factors. The Nordic Epidemiological SIDS Study

The aim of this study was to investigate associations between sudden infant death syndrome (SIDS) and social factors in the Nordic countries. A case-control study was conducted in Denmark, Norway and Sweden: The Nordic Epidemiological SIDS Study. Parents of 244 SIDS infants and 869 control infants matched on gender, age at death and place of birth filled in questionnaires. The dataset was analysed by conditional logistic regression. In univariate analysis, the following sociodemographic factors were associated with an increased risk of SIDS: low maternal age [odds ratio (OR) 7.8; 2.8-21.5], high birth order (OR 4.4; 2.5-7.5), single motherhood (OR 2.9; 1.7-5.0), low maternal education (OR 4.5; 2.8-7.1), low paternal education (OR 3.0; 1.9-4.7), maternal unemployment (OR 2.4; 1.8-3.4) and paternal unemployment (OR 4.0; 2.7-5.9). In a multivariate analysis where maternal smoking was also included, only paternal unemployment, young maternal age and high birth order remained significantly associated with SIDS. Housing conditions were not associated with SIDS. However, the risk of SIDS was high if the family had lived in their present home for only a few years (OR 2.3; 1.3-4.1). Sociodemographic differences remain a major concern in SIDS in a low-incidence situation and even in an affluent population with adequate health services.