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Biomedical subjects

W Nystad

Publications and source records attributed to W Nystad.

At least 19 recordsLinked to original sources
PubMed2001

[Day care centers, infections and asthma].

BACKGROUND: Our objective was to use a causal model for childhood asthma to determine whether the effect of day care attendance on asthma was mediated by recurrent respiratory tract infections. MATERIAL AND METHODS: The study is based on a cross-sectional survey among 1,447 children aged 6-16 years in Oslo. Their parents completed written questionnaires. A recursive logit model was used to estimate direct effects in terms of adjusted odds ratios (aOR). RESULTS: Year of birth, number of siblings and length of maternal education were significantly associated with after-school care attendance. Attendance increased the risk of early infections, aOR = 1.8 (1.3-2.5), and infections were associated with asthma, aOR = 4.9 (3.4-7.3). The crude association between after-school care and asthma was cOR = 1.5 (1.0-2.2), whereas the estimated direct effect was small and non-significant, aOR = 1.2 (0.8-1.9). The results may be influenced by over-reporting of infections among parents with children with asthma. INTERPRETATION: Our results suggest that children who attend day care have an increased risk of asthma, with early infections as a mediator of risk.

Adolescent↗
PubMed2001

Physical activity affects the prevalence of reported wheeze.

The present study examines whether physical activity level (hours per week) among children with and without asthma are associated with the prevalence of reported wheezing and whistling in the chest in the last 12 months. The data are based on a survey of school children, aged 7-16 years (n = 2188), in Oslo in 1994 that employed the ISAAC questionnaire. In children reporting asthma, wheezing and whistling in the chest in the last 12 months was less prevalent among inactive children (66.7%) compared to those who exercised (89.4%) (p = 0.05). The prevalence of wheeze also differed among inactive (4.4%) and active (8.8%) children not reporting asthma (p = 0.02). Positive associations between physical activity and wheezing and whistling in the chest remained present using multiple logistic regression analysis adjusting for sex, age and atopy. Children who are engaged in sports or exercise seem to report asthma symptoms differently than inactive children. These findings raise the question whether level of physical activity could affect some of the variability in reported asthma symptoms when such morbidity is measured as 'wheeze in last 12 months'.

Adolescent↗
PubMed2001

Increased level of bronchial responsiveness in inactive children with asthma.

We estimated the association between bronchial responsiveness and hours of exercise per week in children with and without asthma. A random sample of school children (n = 2188), 6-16 years old, was enrolled in a cross-sectional study of asthma in Oslo using the ISAAC questionnaire. Lung function and bronchial responsiveness (BR) using methacholine was measured in a random sample of 80 children with asthma, wheeze and no asthma/no wheeze. The relation between hours of exercise per week and BR [log (DRS)] was estimated by linear regression. Sex and age were included as covariates. Hours of exercise were categorized in: none, 30 min, 1 h, 2-3 h, 4-6 h and 7 h or more. The mean values of log (DRS) were different in the low and high exercise groups for children with asthma (P = 0.02), whereas there was no effect of exercise on BR for children without asthma. BR increased with decreasing hours of exercise per week in children with asthma. The bronchial responsiveness decreased with 0.11 (95% CI -0.20, -0.01) pr unit in scale. This pattern was not present in children without asthma. The results suggest that there is a relation between hours of exercise per week and bronchial responsiveness in children with asthma.

Adolescent↗
PubMed2000

Asthma and allergy among schoolchildren in a mountainous, dry, non-polluted area in Norway.

The aim of this study was to assess prevalence of asthma and allergy in the non-polluted mountain area of Upper Hallingdal, Norway. All schoolchildren (7-16 years) who in a previous questionnaire survey (n = 1177) reported 'sometime' asthma were enrolled in group I (n = 80), the 59 who reported asthma-like symptoms in the past 12 months formed group II, and 77 of the healthy controls were randomly selected as group III. All 216 children underwent clinical examination, skin prick test, spirometry, bronchial provocation (PD20 metacholine) and treadmill exercise test. Subsequently they were reclassified as (1) healthy, never had asthma or symptoms, (2) symptoms not confirmed as asthma, (3) previous asthma, now healthy, (4) current asthma. Lifetime asthma prevalence was 10.2%. Based upon clinical examination, the specificity and sensitivity of the questionnaire for asthma diagnosis were 88 and 74%, respectively. Forced vital capacity was significantly higher among the asthmatics (group 4 versus 1), whereas forced expiratory volume in one second (FEV1) and forced expiratory flow at 50% of vital capacity were similar in all groups. More than 10% reduction in FEV1 following treadmill-run was found in 20% of children. Children with current asthma compared to controls had significantly; lower mean values of PD20 (9.1 versus 16.5 micromol), higher eosinophil cationic protein (13.4 versus 7.7 micromol) and more frequent sensitization to animal dander (56% versus 10%). In conclusion, despite a favorable climate, little mite sensitization and low outdoor pollution, asthma prevalence was surprisingly high in Upper Hallingdal. Sensitization to animal dander was the most important contributing factor for current asthma.

Adolescent↗
PubMed2000

Asthma.

From an epidemiological point of view four issues are briefly emphasized here: the definition of asthma, time trends and regional differences, and risk factors for asthma. Furthermore, I will focus upon a few aspects regarding the relation between exercise and asthma. The definition of asthma has presented problems for those involved in studying the disease in general populations, where the estimates rely solely on reported asthma and respiratory symptoms. A standardized questionnaire does not fully overcome differences in languages and interpretations of the concepts of asthma and wheeze over time and in different communities. Although the belief of an upward trend of childhood asthma seems to be widely accepted, studies with the proper methodology to investigate this issue are scarce. The prevalence of asthma varies within and between countries. There is no clear urban rural gradient, and the prevalence of atopy appears to be higher in western than in eastern Europe. Amazingly little is still known about genetic and environmental factors that are causally related to the manifestation of allergic disorders in previously asymptomatic individuals. The effect of exercise on asthma may be many-sided. Children with asthma can actively take part in sport. However, to what extent extensive exercise may affect the occurrence of bronchial responsiveness is unclear, and among athletes exercise may be a risk factor for the development of "athlete's asthma". In conclusion, epidemiological studies have to date not reached their potential due to the lack of longitudinal studies including objective measures of exposures and health outcomes. Causal inference is limited, and further studies designed to answer specific research questions are needed.

Asthma↗
PubMed2000

The wheezing schoolchild--an undiagnosed asthmatic. A follow-up of children with parentally reported episodes of wheeze without diagnosed asthma.

OBJECTIVE: To examine children aged 7-15 years with parentally reported episodes of wheeze in order to estimate the proportion of undiagnosed asthmatics in this group. DESIGN: A cross-sectional study with clinical examination of subgroups. SETTING: All children (n = 832) aged 7-15 years in the municipality of Odda. SUBJECT: Based on completed questionnaires, the children were selected to one of four groups: Children with wheeze but no asthma (wheeze group); children with current asthma (asthma group); children with past asthma (past asthma group); and children with neither asthma nor wheeze (control group). MAIN OUTCOME MEASURES: Parental reports of episodes of wheeze, assessment of skin prick test sensitivity, measures of lung function and exercise-induced bronchoconstriction (EIB). RESULTS: In the wheeze group, 3 (7.5%) of 40 children were diagnosed with asthma in the 18-month period between the questionnaire survey and the examination, while 4 (10%) other children had EIB. Another 8 children (20%) reported 3 episodes of wheeze or more, and at least 1 episode during the 12-month period before the clinical examination. Classifying these children as asthmatics would give a proportion of 37.5% with undiagnosed asthma in the wheeze group, and the prevalence of current asthma among children aged 7-15 would rise from 2.9% based on a questionnaire survey to 4.9%. CONCLOSIONS: Using a wide definition of asthma, this study suggests that a large proportion of Norwegian children with wheeze actually have asthma.

Adolescent↗
PubMed2000

Asthma and wheezing among Norwegian elite athletes.

PURPOSE: The objectives were to estimate the prevalence of self-reports of asthma and wheezing among Norwegian elite athletes compared with the general population and to estimate the associations between asthma and types of sports, exercise and team level. METHODS: The study population included all Norwegian elite athletes on the national junior and senior teams in 1997 (N = 1620) and a random sample from the general population (N = 1680). The surveys included items for asthma, respiratory symptoms, the history of participation in sports, sports events, and exercise and team level. The associations between the exposure variables and the outcomes adjusting for potential confounding factors were estimated using logistic regression. Crude (c) and adjusted odds ratio (aOR) with 95% confidence interval (CI) are presented. RESULTS: The prevalence of asthma was greater among athletes (10.0%) compared with that in the general population (6.9%) and remained so after controlling for confounders, aOR = 1.5 (95%CI 1.1-2.1). The risk of asthma was highest in sports requiring strength and endurance. This was the case for comparisons between athletes and the general population, aOR = 3.5 (1.6-7.6) for strength and aOR = 2.2 (1.4-3.5) for endurance sports. Comparisons within the sample of athletes using technical sports as the reference category revealed similar results, aOR = 3.0 (1.1-8.0) and aOR = 2.0 (1.0-4.3), respectively. Furthermore, asthma was more common among female than male athletes (aOR 1.7 (1.1-2.7)). Training more than 20 h x wk(-1) was associated with asthma when compared with levels of training less than 10 h x wk(-1) (aOR 1.9 (1.0-4.1)). CONCLUSION: These results indicate that asthma is more common among athletes compared with the general population. Asthma among athletes may define a subgroup of asthma cases for whom etiology is related to extensive exercise.

Adult↗
PubMed2000

Daycare attendance, asthma and atopy.

The objective of this article is to review studies that have examined the relation of daycare to asthma and atopy. In order to identify studies for inclusion, abstracts of all studies referenced in Medline from January 1966 to January 2000 and in BIBSYS were searched and extracted if they included 'asthma' or 'atopy' combined with words such as 'daycare', 'nursery' or 'kindergarten'. Eight studies fulfilled the criteria of inclusion. The outcomes were asthma, skin prick test (SPT) reactivity, a positive radioallergosorbent test (RAST), hay fever, and eczema. Daycare attendance was positively associated with asthma in five of six studies including asthma. In three of these studies there was no statistically significant association between daycare and asthma. Early start in daycare protected against later asthma in one study. There was a weak, but not a statistically significant positive relation between daycare and atopy in two of three studies when SPT reactivity was used as the outcome. In children of small families early start in daycare protected against atopy. The quality of the studies varies, and they are not directly comparable. The relation between daycare attendance and asthma and atopy is unclear, and further studies designed to answer this specific research question are needed.

Asthma↗
PubMed1999

[What can twin research reveal about the causes of diseases?].

The purpose of this paper is to describe the place of twin studies in etiological research on somatic diseases, using asthma as an example. Twin studies provide answers to the relative importance of genes and environment in the development of disease, but have been criticised for systematic biases especially linked to unusual conditions in twin pregnancies. For asthma, classical twin studies show that genes explain the largest part of the interindividual variability, and that common family environment does not explain similarity in asthma in siblings. The assumptions underlying classical twin studies are discussed. A few other twin designs are mentioned, and we conclude that twin studies still play an important role in understanding causes of somatic diseases.

Asthma↗
PubMed1999

A comparison of VO2(peak) between patients with congenital heart disease and healthy subjects, all aged 8-17 years.

The peak oxygen uptake (VO2(peak)) of 196 healthy children and adolescents aged 8-16 years, and 187 children and adolescents (in the same age range) with congenital heart disease (CHD), was measured using a graded treadmill test (Oslo-protocol). The healthy population was tested to assess the reference values that were to be used in the interpretation of the results obtained from patients with CHD. The results revealed that patients with CHD exhibited lower VO2(peak) values, with declining values for boys after the age of 12-13 years. When separated into different diagnostic groups, on average, patients with a chronic pressure overload of the left ventricle and patients with tetralogy of Fallot have lower VO2(peak) values, but make approximately the same progress with age as healthy subjects. Patients with transposition of the great arteries, however, displayed a marked decline in VO2(peak) after the age of 12-13 years. Whether exercise testing should be included in routine follow-up in patients with CHD, especially those between the ages of 10 and 16 years, when the condition of some patients deteriorates, requires special attention.

Adolescent↗
PubMed1999

Wheezing in school children is not always asthma.

Our objective was to study whether children with reported asthma differed from children with wheeze but without asthma, and from children with neither asthma nor wheeze, regarding lung function, bronchial hyper-responsiveness (BHR) using methacholine inhalation, exercise-induced bronchoconstriction (EIB), and skin prick test (SPT) reactivity. School children (n=2188), enrolled in a survey of asthma, were classified into three mutually exclusive groups by parental report of: asthma, wheeze, and no asthma/no wheeze. A random sample of 80 children in each group was tested (n=240). Among asthmatics, 68% (95% confidence interval (CI), 57-79) had a BHR (measured as PD20 forced expiratory volume in 1 s (FEV1) < or = 8.16 micromol using methacholine) compared to 31% (CI 20-42%) and 30% (CI 19-40%) in the wheeze and no asthma/no wheeze groups. The dose-response slope (DRS) confirmed the PD20 data and distinguished equally between groups. EIB (> or =10% fall in FEV1) was more frequent (40%, CI 29-52%) among asthmatics than among children with wheeze (12%, CI 4-19%) and no asthma/no wheeze (7%, CI 1-13%). The prevalence of at least one positive SPT was twice as high in the asthma group (58%, CI 47-69%) than in the wheeze (27%, CI 16-37%) and the no asthma/no wheeze (25%, CI 15-35%) groups. These results indicate that children with asthma differ from children with wheeze and children with no asthma/no wheeze regarding lung function, BHR, EIB, and SPT reactivity. Children with wheeze are more similar to children with no asthma/no wheeze with respect to these parameters.

Adolescent↗
PubMed1999

Day care attendance, recurrent respiratory tract infections and asthma.

OBJECTIVE: Our objective was to use a causal model for childhood asthma to determine whether the effect of day care attendance on asthma was mediated by recurrent respiratory tract infections. DESIGN: A cross-sectional survey among 1447 children aged 6-16 years in Oslo. Their parents completed written questionnaires. A recursive logit model was used to estimate direct effects in terms of adjusted odds ratios (aOR). RESULTS: Year of birth, number of siblings and length of maternal education were significantly associated with day care attendance. Attendance at day care increased the risk of early infections, aOR = 1.8 (1.3-2.5), and infections were associated with asthma, aOR = 4.9 (3.4-7.3). The crude association between day care and asthma was cOR = 1.5 (1.0-2.2), whereas the estimated direct effect was small and nonsignificant, aOR = 1.2 (0.8-1.9). The results may be influenced by overreporting of infections among parents of children with asthma. CONCLUSIONS: Our results suggest that children who attend day care have an increased risk of asthma with early infections as a mediator of risk.

Absenteeism↗
PubMed1998

[Aerobic capacity in children and adolescents--Nordic results over the past 45 years].

The aim of this study was to reveal whether today's children and adolescents have lower aerobic capacity compared with earlier studies. Aerobic capacity may be defined as the highest amount of oxygen a subject is able to consume per unit of time. Peak oxygen uptake (VO2peak) is often used as a measure of aerobic capacity in children. VO2peak in 196 healthy children and adolescents of both sexes, aged 8-16 years, was measured on a graded treadmill test. The mean results of VO2peak (l.min-1) showed only small differences compared with previous studies in Scandinavia. There was, however, greater dispersion in the present study when the VO2peak-values were corrected for weight (ml.kg-1.min-1) than in the earlier studies. When compared to other countries in Europe, Norwegian subjects achieved higher values. The reason may be due to either genetic differences or to a higher level of physical activity among the Norwegian subjects.

Adolescent↗
PubMed1998

Increasing risk of asthma without other atopic diseases in school children: a repeated cross-sectional study after 13 years.

Some children develop asthma and other atopic diseases, others asthma without atopic diseases. To better understand secular trends, we estimated the relative increase in asthma in children with (atopy related asthma) and without (non-atopy related asthma) other atopic diseases (eczema or hay fever) in two samples of school children born, 1965-1975 (n = 1674) and 1978-1988 (n = 2188). By analysing the samples as historical cohorts, age-specific prevalence rates were estimated and incidence rates were calculated (number of new cases by 1000 person years under risk). Cox regression was used to estimate the relative risk (RR) of asthma by year of birth. The point prevalence of asthma was 1.9% (95% CI: 1.4-2.4) in the 1965-1975 cohort and 4.6% (95% CI: 3.8-5.4) in the 1978-1988 cohort for three-year old children, and remained fairly constant throughout childhood. The age-specific prevalence of non-atopy related asthma increased relatively more from 1965-1975 to 1978-1988 compared to atopy related asthma. The age-specific incidence rates of asthma showed that the RRs comparing the two cohorts tended at all ages to be highest for non-atopy related asthma. The relative risks of non-atopy related asthma by gender and birth cohort, showed that the effect of cohort was higher for non-atopy related asthma, aRR: 4.0 (95 % CI: 2.5-6.5), than for atopy-related asthma aRR: 2.0 (95% CI: 1.3-3.2). Children without other atopic diseases have a higher relative risk of being diagnosed with asthma than children with other atopic diseases across all ages comparing two samples of school children born 1965-1975 and 1978-1988.

Adolescent↗
PubMed1998

Recurrent respiratory tract infections during the first 3 years of life and atopy at school age.

BACKGROUND: The hypothesis that infections reduce the risk of atopy was investigated by estimating the association between recurrent respiratory tract infections during the first 3 years of life and atopy at school age. METHODS: According to surveys in three different areas of Norway, children were classified into three groups: asthma, wheeze without asthma (wheeze), and no asthma/no wheeze. The skin prick test (SPT) was conducted on a stratified random sample of children (n = 502). The outcome was at least one positive SPT. The exposure variable was retrospective parental report of respiratory tract infections during the first 3 years of life. RESULTS: Infections were negatively associated with atopy, crude odds ratio (cOR) = 0.3, 95% confidence interval (95% CI) 0.1-0.7, in the asthma group. A similar association was present in children with wheeze cOR = 0.4 (95% CI 0.1-1.2). The number of siblings was not associated with atopy in any group. Infections remained negatively associated with atopy in children with asthma, aOR = 0.3 (95% CI 0.1-0.7), in a logistic regression model adjusting for confounding factors. A similar pattern was present in the wheeze group. CONCLUSIONS: Recurrent respiratory tract infections during the first 3 years of life are negatively associated with atopy at school age in children with asthma.

Adolescent↗
PubMed1998

Aerobic endurance testing of children and adolescents--a comparison of two treadmill-protocols.

Fifty-eight children and adolescents of both sexes, aged 8-16, were tested on a treadmill using two different protocols. The well-known Bruce-protocol has the disadvantages of steep incline and large increments at each step. A new protocol (Oslo-protocol) with less incline and smaller increments was compared to the Bruce-protocol. The results from the two protocols showed no differences with regard to peak oxygen uptake (VO2peak) or peak heart rate (HRpeak). However, the respiratory exchange ratio (R) and blood lactate concentration [La-] showed higher values when the Bruce-protocol was used. The study also indicated that the often used criteria of HRpeak, R and achievement of a plateau in VO2 to estimate VO2peak, were not reliable indicators in either protocol. When time to exhaustion was used as an estimation of aerobic endurance level, the Oslo-protocol discriminated better than the Bruce-protocol. As a conclusion, the results indicate that none of the criteria may be used as a reliable indicator of having achieved VO2peak. An experienced testleader may be essential to define when VO2peak has been reached in children. On the basis of the results from the current study, the Oslo-protocol seems suitable as a test-protocol when testing children and adolescents for VO2peak.

Adolescent↗
PubMed1997

[Occurrence of asthma among school children in Norway during the period 1985-94].

Several comparable surveys of childhood as have been performed in Norway. This article describes the prevalence among children, 6-13 years old, during the period 1985-94, and how this prevalence is influenced by the operational definition of asthma. Questionnaires were administered in eight areas; Troms/Finnmark (1985), Nordland (1985), Ardal/Laerdal (1989/92), Sør-Varanger (1992), Oslo (1994), Hallingdal (1994) and Odda (1994). The response rates varied from 85 to 96%. The parent-reported lifetime prevalences were lowest in the areas where the studies took place in 1985, the earliest year of study; Nordland 7.2% (95% CI 6.5-7.9), Troms/Finnmark 8.1% (7.4-8.8). The prevalence increased up to 1994, with the highest prevalence in Oslo 13.7% (12.0-15.4). The prevalence of current asthma was about half the lifetime prevalence; Oslo 5.7% (4.6-6.8) compared with 10.1% (8.5-11.6). When respiratory symptoms the estimates were doubled in some areas and regional differences were reduced. The prevalence increased during the study period and seemed to be highest in northern Norway. Regions classified as polluted did not have a higher prevalence.

Adolescent↗