Exposure to Particles and Nitrogen Dioxide Among Workers in the Stockholm Underground Train System.

OBJECTIVES: Exposure to fine particles in urban air has been associated with a number of negative health effects. High levels of fine particles have been detected at underground stations in big cities. We investigated the exposure conditions in four occupational groups in the Stockholm underground train system to identify high-exposed groups and study variations in exposure. METHODS: PM1 and PM2.5 were measured during three full work shifts on 44 underground workers. Fluctuations in exposure were monitored by a real-time particle monitoring instrument, pDR, DataRAM. Qualitative analysis of particle content was performed using inductively coupled plasma mass spectrometry. Nitrogen dioxide was measured using passive monitors. RESULTS: For all underground workers, the geometric mean (GM) of PM1 was 18 µg/m3 and of PM2.5 was 37 µg/m3. The particle exposure was highest for cleaners/platform workers, and the GM of PM1 was 31.6 µg/m3 [geometric standard deviation (GSD), 1.6] and of PM2.5 was 76.5 µg/m3 (GSD, 1.3); the particle exposure was lowest for ticket sellers, and the GM of PM1  was 4.9 µg/m3 (GSD, 2.1) and of PM2.5 was 9.3 µg/m3 (GSD, 1.5). The PM1 and PM2.5 levels were five times higher in the underground system than at the street level, and the particles in the underground had high iron content. The train driver's nitrogen dioxide exposure level was 64.1 µg/m3 (GSD, 1.5). CONCLUSIONS: Cleaners and other platform workers were statistically significantly more exposed to particles than train drivers or ticket sellers. Particle concentrations (PM2.5) in the Stockholm underground system were within the same range as in the New York underground system but were much lower than in several older underground systems around the world.

Sleep as a predictive factor for the onset and resolution of multi-site pain: a 5-year prospective study.

BACKGROUND: Disturbed sleep and pain often co-exist and the relationship between the two conditions is complex and likely reciprocal. This 5-year prospective study examines whether disturbed sleep can predict the onset of multi-site pain, and whether non-disturbed sleep can predict the resolution of multi-site pain. METHODS: The cohort (n = 1599) was stratified by the number of self-reported pain sites: no pain, pain from 1-2 sites and multi-site pain (≥3 pain sites). Sleep was categorized by self-reported sleep disturbance: sleep A (best sleep), sleep B and sleep C (worst sleep). In the no-pain and pain-from-1-2 sites strata, the association between sleep (A, B and C) and multi-site pain 5 years later was analysed. Further, the prognostic value of sleep for the resolution of multi-site pain at follow-up was calculated for the stratum with multi-site pain at baseline. In the analyses, gender, age, body mass index, smoking, physical activity and work-related exposures were treated as potential confounders. RESULTS: For individuals with no pain at baseline, a significantly higher odds ratio for multi-site pain 5 years later was seen for the tertile reporting worst sleep [odds ratio (OR) 4.55; 95% confidence interval (CI) 1.28-16.12]. Non-disturbed (or less disturbed) sleep had a significant effect when predicting the resolution of multi-site pain (to no pain) (OR 3.96; 95% CI 1.69-9.31). CONCLUSION: In conclusion, sleep could be relevant for predicting both the onset and the resolution of multi-site pain. It seems to be a significant factor to include in research on multi-site pain and when conducting or evaluating intervention programmes for pain.

Total desmosines in plasma and urine correlate with lung function.

The aim of the present study was to evaluate the relationship between the matrix degradation biomarkers, desmosine and isodesmosine (desmosines), and lung function. Plasma and creatinine-corrected urinary total desmosines (P- and U-desmosines, respectively), lung function and diffusing capacity of the lung for carbon monoxide (D(L,CO)) were measured in a cohort of subjects from the Swedish Twin Registry. Concentrations of U- and P-desmosines were measured in 349 and 318 subjects, respectively; approximately one-third of subjects had chronic obstructive pulmonary disease (COPD). Age, female sex, body mass index (BMI) and smoking were significantly associated with U-desmosines in a multiple linear regression analysis. In the overall population, after adjustments for age, sex, height, BMI and smoking, concentrations of U-desmosines were significantly correlated with all lung function measures, and P-desmosines with forced expiratory volume in 1 s and D(L,CO) (p<0.05). With the exception of residual volume versus P-desmosines, relationships between concentrations of desmosines and lung function measures were markedly stronger in subjects with COPD compared with those without COPD. These cross-sectional data showing associations between desmosines and several lung function variables suggest that desmosines, particularly U-desmosines, could be a useful biomarker of COPD status.

Health effects of a subway environment in healthy volunteers.

Environmental particle exposure, often estimated as the particulate mass of particles with a diameter <10 microm, <2.5 microm or <1 microm (PM(10), PM(2.5) or PM(1)), is known to have a negative impact on the health of the population. Little is known about how the size and origin of particles influence the effects. We have previously shown that exposure to a road tunnel environment causes a cellular inflammatory response in the airways of healthy individuals. In the present study, our aim was to investigate potential airway health effects from exposure to a subway environment. 20 healthy volunteers were exposed to a subway and a control environment for 2 h, followed by measurements of lung function and the inflammatory response in the lower airways (bronchoscopy) and in the peripheral blood. No cellular response was found in the airways after exposure to the subway environment. In the blood, we found a statistically significant increase in fibrinogen and regulatory T-cells expressing CD4/CD25/FOXP3. Subway and road tunnel environments have similar levels of PM(10) and PM(2.5), whilst the concentrations of ultrafine particles, nitrogen monoxide and dioxide are lower in the subway. Although no cellular response was detected, the findings indicate a biological response to the subway environment. Our studies show that using gravimetric estimates of ambient particulate air pollution alone may have clear limitations in health-risk assessment.

Physical workload, low back pain and neck-shoulder pain: a Swedish twin study.

OBJECTIVES: To investigate if high physical workload is associated with low back pain (LBP) and/or neck-shoulder pain (NSP) when taking into account the influence of genetic and shared environmental factors. Further, the study aims to explore the potential influence of genetic and shared environmental factors in the associations between high physical workload and the three disorder subgroups: solely LBP, solely NSP, and concurrent LBP and NSP. METHODS: Data on 16,107 monozygotic and dizygotic twins, born during 1959-1985, were obtained from a cross-sectional study, performed in 2005-2006 by the Swedish Twin Registry. Odds ratios (ORs) calculated in cohort analyses and co-twin control analyses were used to assess the associations between high physical workload and LBP and NSP when controlling for genetic and shared environmental factors. RESULTS: In the cohort analysis, the association between high physical workload and the group with any one symptom (LBP and/or NSP) was OR 1.47 (95% CI 1.37 to 1.57). The co-twin control analyses indicated that the association was not confounded by genetic and shared environmental factors with OR 1.34 (95% CI 1.02 to 1.75) for dizygotic twins and OR 1.44 (95% CI 1.06 to 1.95) for monozygotic twins. In the cohort analyses the association with high physical workload was higher for concurrent LBP and NSP (OR 1.80 (95% CI 1.62 to 1.99)) than for solely LBP (OR 1.41 (95% CI 1.27 to 1.57)) and solely NSP (OR 1.31 (95% CI 1.20 to 1.43)). Concurrent LBP and NSP was the only group that showed a stepwise decrease of the point estimates between the cohort analysis and the co-twin control analyses, OR 1.71 (95% CI 1.00 to 2.94) for dizygotic twins, and OR 1.29 (95% CI 0.64 to 2.59) for monozygotic twins indicating confounding by genetic and shared environmental factors. CONCLUSIONS: High physical workload was associated with LBP and/or NSP even after adjusting for genetic or shared environmental factors. Only for concurrent LBP and NSP, genetic and shared environmental factors seemed to have an influence on the association with high physical workload.

Blood markers of inflammation and coagulation and exposure to airborne particles in employees in the Stockholm underground.

OBJECTIVES: Although associations have been found between levels of ambient airborne particles and cardiovascular disease (CVD) in the general population, little is known about possible cardiovascular effects from high exposure to particles in underground railway systems. This study investigates risk markers for CVD in employees exposed to particles in the Stockholm underground system. METHODS: 79 workers (54 men and 25 women) in the Stockholm underground were investigated between November 2004 and March 2005. All were non-smokers aged 25-50 years. Three exposure groups were delineated: 29 platform workers with high exposure to particles, 29 train drivers with medium exposure and 21 ticket sellers with low exposure (control group). A baseline blood sample was taken after 2 non-working days, and a second sample after 2 working days, for analysis of levels of plasminogen activator inhibitor-1 (PAI-1), high-sensitivity C-reactive protein (hs-CRP), interleukin-6, fibrinogen, von Willebrand factor and factor VII. The study investigated changes in plasma concentrations between sample 1 and sample 2, and differences in average concentrations between the groups. RESULTS: No changes between sample 1 and 2 were found that could be attributed to particle exposure. However, the highly exposed platform workers were found to have higher plasma concentrations of PAI-1 and hs-CRP than the ticket sellers and train drivers. This suggests that particle exposure could have a long-term inflammatory effect. These differences remained for PAI-1 in the comparison between platform workers and ticket sellers after adjusting for body mass index. CONCLUSIONS: Employees who were highly exposed to airborne particles in the Stockholm underground tended to have elevated levels of risk markers for CVD relative to employees with low exposure. However, the differences observed cannot definitely be linked to particle exposure as such.

Mortality, morbidity and occupational exposure to airway-irritating agents among men with a respiratory diagnosis in adolescence.

OBJECTIVES: To examine the influence of an airway diagnosis in adolescence on future health and occupation in Swedish men. METHODS: Data were collected from the linkage of four Swedish national registers: the Military Service Conscription Register, the Population and Housing Censuses, the Inpatient Care Register and the National Cause of Death Register. A job-exposure matrix for airway-irritating substances was developed for application on the conscription cohort. The cohort included 49 321 Swedish men born 1949-51. Three groups-(1) healthy, (2) asthmatics (mild and severe asthma) and (3) subjects with allergic rhinitis without concurrent asthma-were identified at conscription and analysed for mortality, in-patient care and strategies for choice of occupation with emphasis on airway-irritating job exposure. Analyses were adjusted for smoking and childhood socioeconomic position. RESULTS: The prevalence of total asthma was 1.8%, severe asthma 0.45% and allergic rhinitis 2.7%. Mortality for all causes was significantly higher in total asthma, hazard ratio (HR) 1.49 (95% CI 1.00 to 2.23), and lower in allergic rhinitis, HR 0.52 (95% CI 0.30 to 0.91). Asthma was a risk factor for inpatient care while allergic rhinitis was associated with less in-patient care (odds ratio (OR) for total asthma 1.16 (95% CI 1.00 to 1.34), severe asthma 1.38 (95% CI 1.04 to 1.85), allergic rhinitis 0.92 (95% CI 0.82 to 1.03)). Those with asthma tended to avoid jobs with a high probability for airway-irritating exposure (OR 0.88, 95% CI 0.71 to 1.09), but not to the same extent as subjects with allergic rhinitis (OR 0.58, 95% CI 0.47 to 0.70) (ORs from 1990). CONCLUSION: Subjects with asthma did not change their exposure situation to the same extent as subjects with allergic rhinitis. Further, asthmatics had an increased risk for morbidity and mortality compared to healthy subjects and subjects with allergic rhinitis.

Road tunnel air pollution induces bronchoalveolar inflammation in healthy subjects.

Traffic-related air pollution is associated with adverse respiratory effects. The aim of the present study was to investigate whether exposure to air pollution in a road tunnel causes airway inflammatory and blood coagulation responses. A total of 16 healthy subjects underwent bronchoscopy with bronchial mucosal biopsies and bronchoalveolar lavage (BAL) on two occasions, in random order: once at 14 h after a 2-h exposure to air pollution in a busy road tunnel, and once after a control day with subjects exposed to urban air during normal activities. Peripheral blood was sampled prior to bronchoscopy. The road tunnel exposures included particulate matter with a 50% cut-off aerodynamic diameter of 2.5 microm, particulate matter with a 50% cut-off aerodynamic diameter of 10 mum and nitrogen dioxide which had median concentrations of 64, 176 and 230 microg.m(-3), respectively. Significantly higher numbers of BAL fluid total cell number, lymphocytes and alveolar macrophages were present after road tunnel exposure versus control. Significantly higher nuclear expression of the transcription factor component c-Jun was found in the bronchial epithelium after exposure. No upregulation of adhesion molecules or cellular infiltration was present and blood coagulation factors were unaffected. In conclusion, exposure of healthy subjects to traffic-related air pollution resulted in a lower airway inflammatory response with cell migration, together with signs of an initiated signal transduction in the bronchial epithelium.

Negligible clearance of ultrafine particles retained in healthy and affected human lungs.

Ambient particles are believed to be a specific health hazard, although the underlying mechanisms are not fully understood. There are data in the literature indicating fast and substantial systemic uptake of particles from the lung. The present authors have developed an improved method to produce ultrafine particles with more stable radiolabelling and defined particle size range. Fifteen subjects inhaled technetium 99m (99mTc)-labelled carbonaceous particles of 100 nm in size. Radioactivity over the lung was followed for 70 h. The clearance of these ultrafine particles from the lungs and specifically translocation to the circulation was tested. Lung retention for all subjects at 46 h was mean+/-sd 99+/-4.6%. Cumulative leaching of 99mTc activity from the particles was 2.6+/-0.96% at 70 h. The 24-h activity leaching in urine was 1.0+/-0.55%. No evidence of a quantitatively important translocation of 100-nm particles to the systemic circulation from the lungs was found. More research is needed to establish if the approximately 1% cleared activity originates from leached activity or insoluble translocated particles, and whether a few per cent of translocated particles is sufficient to cause harmful effects.

Long-term clearance from small airways decreases with age.

The prevalence of respiratory symptoms increases with age. Age has been found to be negatively associated with large airway clearance. The small airways region is considered important for development of airway disease. Clearance after the first 24 h was studied in 46 healthy subjects with a wide age distribution, (mean 42, range 19-81 yrs). All subjects inhaled monodisperse 6 microm Teflon particles labelled with 111In, with an extremely slow inhalation flow (0.05 L.s-1). The particles were mainly deposited in the small conducting airways. Lung retention was measured at 0 and 24 h, and at 7, 14 and 21 days after inhalation. Significant relationships were found for the individual 24 h "large" airway clearance in per cent of initial lung deposition with age, forced expiratory volume in one second and forced vital capacity. Age was negatively associated with "small" airway clearance after 24 h as estimated at 2, 7, 14 and 21 days. Using stepwise linear regression only age remained significantly associated to clearance. In conclusion, small airway clearance over 21 days was found to decrease with age. This might be one factor associated with the high prevalence of respiratory symptoms associated among the elderly.

Long-term clearance from small airways in patients with cystic fibrosis.

Impaired mucociliary clearance is a hallmark of cystic fibrosis (CF). Early morphological changes first appear in the small airways. Lung clearance was investigated in 11 young CF adults with mild-to-moderate lung disease using a method depositing particles mainly in the small airways. Radiolabelled Teflon particles (6 microm) were inhaled with an extremely slow inhalation flow, 0.05 L x s(-1). Lung retention was measured immediately following inhalations and, on four occasions up to 21 days. The results were compared with data from healthy subjects. The lung retention at 24 h in % of deposition was 67% (95% confidence interval 58-76) in the CF patients, compared to 48% (42-53) in the healthy subjects. Clearance on days 1-7 was larger in the CF patients, 22% (15-29) compared to the healthy subjects, 14% (12-16). No difference was observed between the CF patients and the healthy subjects in the slow clearance phase at day 7 to day 21, representing small airway clearance. Impaired mucociliary clearance in CF patients results in increased 24-h retention and a prolonged rapid clearance phase. The results of the study do not support the current authors' hypothesis that clearance from small airways is slower in cystic fibrosis patients compared to healthy subjects. Furthermore, the data suggest that mucociliary transport is not the dominant clearance mechanism in small airways.

IgE-sensitization to predatory mites and respiratory symptoms in Swedish greenhouse workers.

BACKGROUND: Predatory mites are used as biological pesticides worldwide for control of spider mites and other pests in greenhouses. The aim of this study was to evaluate the impact of occupational exposure to Phytoseiulus persimilis and Hypoaspis miles on IgE sensitization among a large group of Swedish greenhouse workers and to examine the relationship between exposure and allergic asthma and rhinoconjunctivitis. METHODS: A total of 96 greenhouse workers from the southern part of Sweden, who were using the predatory mites for control of pests, were investigated with a questionnaire and a medical examination including lung function test. Blood samples were taken to test for allergen-specific IgE antibodies to Phytoseiulus persimilis and Hypoaspis miles as well as to Tetranychus urticae, Dermatophagoides pteronyssinus/farinae and Tyrophagus putrescentiae. RESULTS: Seventeen of the 96 workers were positive in ImmunoCAP to predatory mites: 17 to P. persimilis (17.7%) and 14 to H. miles (14.6%). Subjects sensitized to predatory mites were significantly more often atopic (13/17), defined as a positive Phadiatop, than those who lacked IgE against these mite species (17/79) (P <0.01). IgE antibodies to the red spider mite T. urticae were present among 23 subjects. Thirty-five of the investigated subjects displayed a positive ImmunoCAP to at least one of the investigated mite species. Furthermore, sensitization to any of the mites tested was significantly associated with asthma (OR=9.3) and rhinoconjunctivitis (OR=4.3). CONCLUSIONS: IgE sensitization to predatory mites, P. persimilis and H. miles, is common among greenhouse workers. The findings stress the importance of improved allergen avoidance in greenhouse environments.

Radionuclide biokinetics database (RBDATA-EULEP): an update.

The main activity of the RBDATA-EULEP project is the development of an electronic database of information on the biokinetics of radionuclides after intake by inhalation, ingestion or injection. It consists of linked tables of publications and experiments, with details and comments on the materials, procedures and results. By March 2004 it contained information on more than 1600 experiments from 600 publications. It will be extended and Internet access will also be provided.

Indoor exposures and recurrent wheezing in infants: a study in the BAMSE cohort.

AIM: The aim of this study was to examine the relationship between indoor exposures and the home environment, and the development of recurrent wheezing during infancy. METHODS: A birth cohort, comprising 4089 children, was followed. Information on exposures was obtained shortly after birth, and episodes of wheezing were recorded when the infants were 1 and 2 y of age. In a nested case-control study, 181 infants were enrolled, who had three or more reported episodes of wheezing after 3 mo of age combined with either use of inhaled steroids or symptoms of bronchial hyper-reactivity, and 359 age-matched controls. Home inspections were performed during the winter following enrolment, and indoor conditions were measured. RESULTS: Adjusted odds ratios (OR) and 95% confidence intervals (CI) were calculated. The OR for recurrent infant wheezing associated with signs of dampness reported prospectively by parents was 1.4 (0.9-2.2), and the OR for observed signs of dampness at home inspections was 1.6 (1.0-2.5). A trend was found in the risk of recurrent wheezing in relation to the number of indicators of dampness: OR 1.3 (0.8-2.2) for one sign of dampness and OR 2.7 (1.3-5.4) for three or more signs of dampness. Newly painted surfaces in the child's bedroom was associated with an increased OR for recurrent wheezing: 1.7 (1.3-2.6). CONCLUSION: Indicators of dampness, as well as recently repainted interior surfaces, appear to be associated with recurrent infant wheezing, with a strengthened effect of combined indoor exposures.

Influence of male sex and parental allergic disease on childhood wheezing: role of interactions.

BACKGROUND: Boys have been reported to be more susceptible to childhood wheezing, whereas girls are more susceptible later in life. This difference might be related to both genetic and environmental factors. OBJECTIVE: To investigate the influence of male sex and parental allergic disease on the development of childhood wheezing. METHODS: Infants (n=4089) born in Stockholm were recruited in a prospective study, BAMSE. Data on parental allergic diseases were obtained from questionnaires answered at the children's birth and on symptoms of wheezing at 1, 2 and 4 years of age. Sensitization to inhalant allergens and lung function was investigated at the age of 4 years. RESULTS: Children were classified as having recurrent, transient (n=266), early-onset persistent (n=319) and late-onset wheezing (n=195). Boys were over-represented in all groups of wheezing (odds ratio, OR=1.4-1.5) and both maternal and paternal allergic disease was of importance for the wheezing outcomes. A dominating influence from maternal allergic disease was only seen in children with persistent wheezing. An interaction exceeding additivity was found between male sex and parental allergic disease, particularly in children with persistent wheezing (OR=2.9 and 95% confidence interval, CI 95% 2.1-4.0 for boys with any parental history vs. OR=1.4, CI 95% 1.0-2.1 for girls). Interaction between male sex and parental allergic disease was also observed in children who wheezed at the age of 4 years and were sensitized to inhalant allergens. CONCLUSION: Our data suggest an interaction between male sex and parental allergic disease in childhood wheezing, which may represent a sex-specific genetic influence.

Building characteristics, indoor air quality and recurrent wheezing in very young children (BAMSE).

This study was conducted to examine the impact of building characteristics and indoor air quality on recurrent wheezing in infants. We followed a birth cohort (BAMSE) comprising 4089 children, born in predefined areas of Stockholm, during their first 2 years of life. Information on exposures was obtained from parental questionnaires when the children were 2 months and on symptoms and diseases when the children were 1 and 2 years old. Children with recurrent wheezing, and two age-matched controls per case, were identified and enrolled in a nested case-control study. The homes were investigated and ventilation rate, humidity, temperature and NO2 measured. We found that living in an apartment erected after 1939, or in a private home with crawl space/concrete slab foundation were associated with an increased risk of recurrent wheezing, odds ratio (OR) 2.5 (1.3-4.8) and 2.5 (1.1-5.4), respectively. The same was true for living in homes with absolute indoor humidity >5.8 g/kg, OR 1.7 (1.0-2.9) and in homes where windowpane condensation was consistently reported over several years, OR 2.2 (1.1-4.5). However, air change rate and type of ventilation system did not seem to affect the risk. In conclusion, relatively new apartment buildings, single-family homes with crawl space/concrete slab foundation, elevated indoor humidity, and reported wintertime windowpane condensation were associated with recurrent wheezing in infants. Thus, improvements of the building quality may have potential to prevent infant wheezing.

Family history and risk of atopic dermatitis in children up to 4 years.

BACKGROUND: The aetiology of atopic dermatitis (AD) is presumably multi-factorial, with interactions between genetic and environmental factors. OBJECTIVE: To investigate the relation between atopic family history and development of AD up to 4 years. METHODS: Using annual questionnaires, we studied the cumulative incidence of AD in 0-4-year-olds in a prospective birth cohort of 4089. Atopic diseases in parents and siblings were recorded at birth. The occurrence of serum immunoglobulin E (IgE) antibodies to inhalant and food allergens was analysed in 2614 4-year-olds, and AD was divided into non-IgE-associated and IgE-associated. RESULTS: Of the children without atopic parents, 27.1% developed AD; of those with single or double parental atopic history, 37.9% and 50.0%, respectively, did so. The effects of parental history of eczema and of atopic respiratory disease (ARD) did not differ significantly, nor did those of maternal and paternal history. Parental history of ARD increased the risk significantly more for IgE-associated AD than for non-IgE-associated AD (odds ratio (OR) 2.0; 95% confidence interval (CI) 1.5-2.8 vs. OR 1.3; 95% CI 1.0-1.8), whereas the two forms lacked major differences in the effect of parental eczema. A history of eczema in older siblings was a risk indicator for both forms of AD (OR 2.1; 95% CI 1.4-3.3 vs. OR 1.8; 95% CI 1.2-2.6). CONCLUSIONS: We found no difference between the effects of maternal and paternal atopic history. Parental eczema was a risk factor for AD irrespective of its association with IgE, but parental history of ARD mainly increased the risk of IgE-associated AD.

Direct and indirect exposure to pets - risk of sensitization and asthma at 4 years in a birth cohort.

INTRODUCTION: There are conflicting data on the association between early exposure to pets and allergic diseases. Bias related to retrospective information on pet ownership has been addressed as a reason for distorted study results. OBJECTIVE: To elucidate how early exposure to cat and dog relates to IgE-sensitization and asthma in children at 2 and 4 years of age, in a prospective birth-cohort study. METHODS: Four thousand and eighty-nine families with children born 1994-1996 in predefined areas of Stockholm answered questionnaires on environmental factors and symptoms of allergic disease at birth, one, two and four years of age. Dust samples collected from the mothers' beds at birth were analysed for Fel d 1 and Can f 1 in a subgroup of the cohort. Blood samples taken at four years from 2614 children were analysed for allergen-specific IgE to common airborne allergens. Risk associations were calculated with a multiple logistic regression model, with adjustment for potential confounders. RESULTS: A correlation was seen between allergen levels and reported exposure to cat and dog. Exposure to cat seemed to increase the risk of cat sensitization, OR (odds ratio) 1.44 (95% confidence interval 1.03-2.01), whereas dog exposure did not have any effect on dog sensitization, OR 1.16 (0.79-1.72). Dog ownership was related to a reduced risk of sensitization to other airborne allergens, OR 0.36 (0.15-0.83), and a similar tendency was seen for cat ownership OR 0.63 (0.37-1.07). Early dog ownership seemed to be associated with a lower risk of asthma, OR 0.50 (0.24-1.03), with no corresponding effect after cat ownership, OR 0.88 (0.56-1.38). CONCLUSION: Early exposure to cat seems to increase the risk of sensitization to cat but not of asthma at 4 years of age. Dog ownership, on the other hand, appears to be associated with lowered risk of sensitization to airborne allergens and asthma. Both aetiological relationships and selection effects have to be considered in the interpretation of these findings.

Strategies for preventing wheezing and asthma in small children.

OBJECTIVE: To assess the effects of living in agreement with allergy preventive guidelines on wheezing and asthma at 2 years of age. DESIGN: Prospective birth cohort study (BAMSE). Questionnaires on heredity and environmental factors were answered when the child was 2 months, and detailed questionnaires on symptoms at 1 and 2 years of age. PARTICIPANTS: 4089 children, born during 1994-1996. SETTING: Child Health Centres in central and north-western parts of Stockholm, Sweden. MAIN OUTCOME MEASURES: Wheezing and asthma up to the age of 2. RESULTS: The effects of preventive guidelines regarding breastfeeding, maternal tobacco smoke and home dampness on wheezing and asthma were assessed in multiple logistic regression models. The cumulative incidence of recurrent wheezing at 2 years of age was 12.6% and of asthma 6.8% among those with a lifestyle in agreement with all guidelines and 24.1 and 17.9%, respectively, in families exposed to at least two of the three risk factors. Among children with no heredity, family lifestyle according to the guidelines gave a twofold reduction of asthma (5.3 vs. 10.5%), while the group with heredity had a threefold reduction (9.1 vs. 27.3%). The attributable fraction for asthma associated with the guidelines was 23% in total and 33% among those with heredity. CONCLUSION: In this observational study, family lifestyle according to preventive guidelines is associated with an important reduction of recurrent wheezing and asthma at 2 years of age, especially among children with allergic heredity. A follow-up will determine whether there still a risk reduction of both symptoms and disease.

The need for a focus on air pollution research in the elderly.

During recent years an increasing focus has been directed towards the adverse health effects associated with ambient air pollution. Elderly people appear to be particularly susceptible to the adverse effects involving the respiratory and cardiovascular systems, resulting in symptoms, exacerbations of disease and even mortality. From an epidemiological point of view it is essential to obtain a more detailed description and identification of factors associated with these health effects. Novel study designs are needed with complementary exposure and biomedical characterisation. Long-term prospective studies are required. A better understanding of the pathophysiological mechanisms is considered important and requires an interaction between epidemiological and mechanistic studies in elderly individuals with or without complementary diseases that put in them especially at risk. Generally a synergy between complementary disciplines is warranted to move this important research area forward, also including in vitro models of cell responses in the elderly, animal models of diseases of the elderly, together with controlled air pollution exposure studies identifying health-related events and mechanisms. The generation of an understanding of air pollution effects in the elderly, at an elevated level, is a prerequisite to substantially reducing the adverse health effects of this population group. At local, national and European Union levels, some steps have been taken to support the research in this area. A major focus on the adverse air pollution effects in the elderly requires a long-term commitment that still remains to be established.