Spontaneous sigh rates during sedentary activity: watching television vs reading

Associations of physical condition with lung function and asthma in adolescents from the general population

BACKGROUND

The relation of physical condition with respiratory outcomes in adolescents is unclear. We examined the hypothesis that adolescents with a lower physical condition represented by a lower cardiorespiratory fitness and physical activity, and a higher screen time have a lower lung function and higher risk of asthma.

METHODS

In a population-based prospective cohort study on 4854 children aged 13 years, we assessed cardiorespiratory fitness by using the peak work rate measured by the steep ramp test. Information on physical activity and screen time was obtained by self-reported questionnaires. Lung function was measured by spirometry and current asthma was assessed by a parental-reported questionnaire.

RESULTS

Taking sociodemographic, lifestyle, and growth-related confounders and multiple hypothesis testing into account, a 1 SD lower cardiorespiratory fitness was associated with a lower FEV₁ , FVC, and FEF₇₅ (Z-score difference (95% CI): -0.31 (-0.35, -0.28), -0.30 (-0.33, -0.26), -0.13 (-0.17, -0.10), respectively), and a higher risk of asthma (Odds Ratio (95% CI) 1.25 (1.06, 1.46)). A 1 SD higher screen time was associated with a lower FVC (Z-score difference (95% CI): -0.06 (-0.10, -0.03)). Physical activity and screen time were not related to asthma. Results did not materially change after additional adjustment for respiratory outcomes at an earlier age.

CONCLUSION

Adolescents with a lower cardiorespiratory fitness had a lower lung function and a higher risk of asthma. Those with a higher screen time had a lower FVC. Further studies are needed to explore the effect of improvements in physical condition on long-term respiratory outcomes.

Sedentary behavior is associated with chronic obstructive pulmonary disease: A generalized propensity score-weighted analysis

Chronic obstructive pulmonary disease (COPD) is the fourth and third leading cause of death worldwide and in China, respectively. Sedentary behavior has been shown to increase the risk of respiratory disease, such as asthma. However, the relationship between sedentary behavior and COPD is unclear. This study aimed to investigate the association between sedentary behavior and COPD.Data was extracted from the 2018 a large-scale cross-sectional study of Chronic Disease and Lifestyle Population Survey in Sichuan Province of China, in which sedentary behavior and chronic diseases were self-reported according to medical records. The association between sedentary behavior on risk of COPD was estimated using multivariable regression model in non-matching cohorts and generalized propensity score-weighted (GPSW)cohorts, respectively, controlling for potential confounders.Individuals who remained sedentary for more than 7 hours per day were more likely to have COPD than the control group (<3 hours) both in conventional multivariate logistic regression analysis (OR = 2.020, 95%CI: 1.575-2.585, P < .001) and GPSW analysis (OR = 2.381, 95%CI: 1.778-3.188, P < .001). After GPSW and the sensitivity analysis using refined smoking variable further found a dose-effect between sedentary behavior and COPD, with 1.242 (95%CI: 1.006-1.532, P < .05) times risk of COPD in those sedentary behavior of more than 5 hours per day (GPSW) and 1.377 (95%CI: 1.092-1.736, P < .05) times risk in those sedentary behavior above 5 hours per day (sensitivity analysis), comparing with the control group.Sedentary behavior is independently associated with increased risk of COPD, adjusting for other confounders. The findings of this study have important implications for future research and public health guidance. Reducing sedentary time may have a significant role in COPD prevention.

Shortening of airway smooth muscle is modulated by prolonging the time without simulated deep inspirations in ovine tracheal strips

The shortening of airway smooth muscle (ASM) is greatly affected by time. This is because stimuli affecting ASM shortening, such as bronchoactive molecules or the strain inflicted by breathing maneuvers, not only alter quick biochemical processes regulating contraction but also slower processes that allow ASM to adapt to an ever-changing length. Little attention has been given to the effect of time on ASM shortening. The present study investigates the effect of changing the time interval between simulated deep inspirations (DIs) on ASM shortening and its responsiveness to simulated DIs. Excised tracheal strips from sheep were mounted in organ baths and either activated with methacholine or relaxed with isoproterenol. They were then subjected to simulated DIs by imposing swings in distending stress, emulating a transmural pressure from 5 to 30 cmH₂O. The simulated DIs were intercalated by 2, 5, 10, or 30 min. In between simulated DIs, the distending stress was either fixed or oscillating to simulate tidal breathing. The results show that although shortening was increased by prolonging the interval between simulated DIs, the bronchodilator effect of simulated DIs (i.e., the elongation of the strip post- vs. pre-DI) was not affected, and the rate of re-shortening post-simulated DIs was decreased. As the frequency with which DIs are taken increases upon bronchoconstriction, our results may be relevant to typical alterations observed in asthma, such as an increased rate of re-narrowing post-DI.NEW & NOTEWORTHY The frequency with which patients with asthma take deep inspirations (DIs) increases during bronchoconstriction. This in vitro study investigated the effect of changing the time interval between simulated DIs on airway smooth muscle shortening. The results demonstrated that decreasing the interval between simulated DIs not only decreases shortening, which may be protective against excessive airway narrowing, but also increases the rate of re-shortening post-simulated DIs, which may contribute to the increased rate of re-narrowing post-DI observed in asthma.

Physical activity among children with asthma: Cross-sectional analysis in the UK millennium cohort

BACKGROUND

Although beneficial for health and well-being, most children do not achieve recommended levels of physical activity. Evidence for children with asthma is mixed, with symptom severity rarely considered. This paper aimed to address this gap.

METHODS

We analyzed cross-sectional associations between physical activity and parent-reported asthma symptoms and severity for 6497 UK Millennium Cohort Study 7-year-old participants (3321, [49%] girls). Primary outcomes were daily moderate-to-vigorous physical activity (MVPA, minutes) and proportion of children achieving recommended minimum daily levels of 60 minutes of MVPA. Daily steps, sedentary time, and total activity counts per minute (cpm) were recorded, as were parent-reported asthma symptoms, medications, and recent hospital admissions. Associations were investigated using quantile (continuous outcomes) and Poisson (binary outcomes) regression, adjusting for demographic, socioeconomic, health, and environmental factors.

RESULTS

Neither asthma status nor severity was associated with MVPA; children recently hospitalized for asthma were less likely to achieve recommended daily MVPA (risk ratio [95% confidence interval [CI]]: 0.67 [0.44, 1.03]). Recent wheeze, current asthma, and severe asthma symptoms were associated with fewer sedentary hours (difference in medians [95% CI]: -0.18 [-0.27, -0.08]; -0.14 [-0.24, -0.05]; -0.15, [-0.28, -0.02], respectively) and hospital admission with lower total activity (-48 cpm [-68, -28]).

CONCLUSION

Children with asthma are as physically active as their asthma-free counterparts, while those recently hospitalized for asthma are less active. Qualitative studies are needed to understand the perceptions of children and families about physical activity following hospital admission and to inform support and advice needed to maintain active lifestyles for children with asthma.

Asthma, exercise and metabolic dysregulation in paediatrics

Asthma is the most frequent chronic disease in childhood. Chest tightness, cough, wheezing and dyspnoea during or after exercise may be unique manifestations of asthma in up to 90% of subjects. Physical activity may be reduced by uncontrolled asthma symptoms and parental beliefs, impairing physical fitness of asthmatic children. Clinicians working in the field of allergy are aware of evidence supporting the benefits of physical activity for patients with asthma. Treatment of asthma is required in order to obtain its control and to avoid any limitation in sports and active play participation. As exercise performance in children with controlled asthma is not different from that of healthy controls, any exercise limitation cannot be accepted. Overweight and obesity may interfere with asthma and exercise, leading to dyspnoea symptoms. Evidences on the effect of insulin resistance on airway smooth muscle and on bronchial hyperactivity are presented. CONCLUSION: Exercise is part of the strategy to obtain the best control of asthma in childhood, but we have to optimise the asthma control therapy before starting exercise programming. Furthermore, it is crucial to give best attention on the effects of obesity and insulin resistance, because they could in turn influence patients' symptoms.

The Strain on Airway Smooth Muscle During a Deep Inspiration to Total Lung Capacity

The deep inspiration (DI) maneuver entices a great deal of interest because of its ability to temporarily ease the flow of air into the lungs. This salutary effect of a DI is proposed to be mediated, at least partially, by momentarily increasing the operating length of airway smooth muscle (ASM). Concerningly, this premise is largely derived from a growing body of in vitro studies investigating the effect of stretching ASM by different magnitudes on its contractility. The relevance of these in vitro findings remains uncertain, as the real range of strains ASM undergoes in vivo during a DI is somewhat elusive. In order to understand the regulation of ASM contractility by a DI and to infer on its putative contribution to the bronchodilator effect of a DI, it is imperative that in vitro studies incorporate levels of strains that are physiologically relevant. This review summarizes the methods that may be used in vivo in humans to estimate the strain experienced by ASM during a DI from functional residual capacity (FRC) to total lung capacity (TLC). The strengths and limitations of each method, as well as the potential confounders, are also discussed. A rough estimated range of ASM strains is provided for the purpose of guiding future in vitro studies that aim at quantifying the regulatory effect of DI on ASM contractility. However, it is emphasized that, owing to the many limitations and confounders, more studies will be needed to reach conclusive statements.

Screen-based sedentary behavior during adolescence and pulmonary function in a birth cohort

Background

Adolescents spend many hours in sitting activities as television viewing, video game playing and computer use. The relationship between sedentary behavior and respiratory health remains poorly elucidated. To date there have been no studies evaluating the relationship between sedentary behavior and pulmonary function in young populations. The purpose of this study is to examine the association between the trajectory of screen-based sedentary behavior from 11 to 18 years and pulmonary function at 18 years in a Brazilian birth cohort.

Methods

Data from a longitudinal prospective study conducted among the participants of the 1993 Pelotas (Brazil) Birth Cohort. Time spent on television, video games, and computers during a weekday was self-reported at ages 11, 15 and 18 years. For each age, sedentary behavior was defined as the sum of time spent on these screen-based activities. To evaluate the sedentary behavior trajectory during adolescence group-based trajectory modeling was used. Outcome variables were three pulmonary function parameters: forced expiratory volume in one second (FEV₁), forced vital capacity (FVC), and peak expiratory flow (PEF), evaluated by spirometry, at 18 years expressed as z-scores. Crude and adjusted linear regressions, stratified by sex, were performed.

Results

The three-group trajectory of sedentary behavior was the best fitting model. The trajectory groups were: always high (representing 38.8% of the individuals), always moderate (54.1%), and always low (7.1%). In the adjusted analyses, boys in the always-low group for sedentary behavior had higher FVC at 18 years (β = 0.177; 95% CI:0.027;0.327; p = 0.021) than boys in the always-high group. There were no differences for other pulmonary function parameters in boys. No significant association was found for girls.

Conclusion

The trajectory of screen-based sedentary behavior throughout adolescence was not consistent associated with pulmonary function at 18 years.

Electronic supplementary material

The online version of this article (doi:10.1186/s12966-017-0536-5) contains supplementary material, which is available to authorized users.

The allergy epidemics: 1870-2010

Before the first description of hay fever in 1870, there was very little awareness of allergic disease, which is actually similar to the situation in prehygiene villages in Africa today. The best explanation for the appearance and subsequent increase in hay fever at that time is the combination of hygiene and increased pollen secondary to changes in agriculture. However, it is important to remember that the major changes in hygiene in Northern Europe and the United States were complete by 1920. Asthma in children did not start to increase until 1960, but by 1990, it had clearly increased to epidemic numbers in all countries where children had adopted an indoor lifestyle. There are many features of the move indoors that could have played a role; these include increased sensitization to indoor allergens, diet, and decreased physical activity, as well as the effects of prolonged periods of shallow breathing. Since 1990, there has been a remarkable increase in food allergy, which has now reached epidemic numbers. Peanut has played a major role in the food epidemic, and there is increasing evidence that sensitization to peanut can occur through the skin. This suggests the possibility that changes in lifestyle in the last 20 years could have influenced the permeability of the skin. Overall, the important conclusion is that sequential changes in lifestyle have led to increases in different forms of allergic disease. Equally, it is clear that the consequences of hygiene, indoor entertainment, and changes in diet or physical activity have never been predicted.

Mechanisms of obesity in asthma

PURPOSE OF REVIEW

Obesity and asthma are chronic conditions affecting millions of people worldwide. The two conditions also appear to be linked with an increased risk of asthma in people who are obese. The purpose of this review is to describe mechanism(s) that may explain the association between asthma and obesity.

RECENT FINDINGS

Current evidence suggests that the association between asthma and obesity is linked by two major phenotypes and three important pathways of obesity-related asthma: one phenotype with primary (often atopic) asthma that is aggravated by obesity and a second phenotype with late-onset nonatopic asthma, which predominantly affects women and primarily seems to be associated with neutrophilic inflammation. Proposed pathways include the mechanical effects of obesity (fewer deep inspirations leading to increased airway hyperresponsiveness), an inflammatory pathway driven by obesity-related cytokines (adipokines), and finally environment and lifestyle changes that have led to an increasing prevalence of obesity over the past 50 years (including exposures in utero, physical activity, and diet) may also result in asthma in predisposed individuals. How these environmental changes influence the occurrence and expression of asthma may depend on the age of exposure and on interactions with genetic susceptibilities.

SUMMARY

Future research should be directed to shed light on the associations between obesity and asthma phenotypes, modern lifestyles and environmental exposures and genetic susceptibilities.

VIDEO ABSTRACT

http://links.lww.com/COAI/A6.

Physical fitness and amount of asthma and asthma-like symptoms from childhood to adulthood

OBJECTIVE

The potential benefits of physical activity on the development of respiratory symptoms are not well known. The present study investigated the longitudinal association between physical fitness and the development of asthma-like symptoms from childhood to adulthood in a longitudinal community-based study.

METHODS

Participants were assessed at ages 9, 15, 20 and 29 years. Asthma-like symptoms and physical fitness was assessed at each age.

RESULTS

Tracking for physical fitness was high from age 9 to 29 years. Using logistic regression, high physical fitness at age 9 predicted a lower prevalence of asthma-like symptoms at ages 9, 20 and 29 years. Asthma at age 9 and female sex and smoking at any age were also independently associated with the presence of asthma-like symptoms. Our findings suggest that the risk for the development of asthma is reduced by 3% and of asthma-like symptoms reduced by 2% from early adolescence to young adulthood (ages 9-29 years) by increasing the maximal workload with 1 W/kg.

CONCLUSION

This finding provide further evidence of a possible beneficial effect of physical activity in childhood on the development of respiratory symptoms in adulthood and supports the notion that the lower levels of physical activity in recent decades may have contributed to an increase in the prevalence of asthma and asthma-like symptoms.

Physical deconditioning as a cause of breathlessness among obese adolescents with a diagnosis of asthma

BACKGROUND

Obese children frequently complain of breathlessness. Asthma and obesity can both contribute to the symptoms during exercise, and this symptom can contribute to a diagnosis of asthma in these children. Despite the high prevalence of obesity few studies have investigated the cardiopulmonary physiology of breathlessness in obese children with a diagnosis of asthma.

METHODS

In this case-control study, thirty adolescents between age 12 and 19 were studied with baseline spirometry and a cardiopulmonary exercise test. Ten adolescents were normal controls, ten had obesity without a diagnosis of asthma, and ten had obesity with a history of physician-diagnosed asthma.

RESULTS

Baseline characteristics including complete blood count and spirometry were comparable between obese adolescents with and without a diagnosis of asthma. During exercise, obese asthmatic and obese non-asthmatic adolescents had significantly reduced physical fitness compared to healthy controls as evidenced by decreased peak oxygen uptake after adjusting for actual body weight (21.7 ± 4.5 vs. 21.4 ± 5.4 vs. 35.3 ± 5.8 ml/kg/min, respectively). However, pulmonary capacity at the peak of exercise was comparable among all three groups as evidenced by similar pulmonary reserve.

CONCLUSION

In this study, breathlessness was primarily due to cardiopulmonary deconditioning in the majority of obese adolescents with or without a diagnosis of asthma.

Physical activity and lung function in adolescents: the 1993 Pelotas (Brazil) birth cohort study

PURPOSE

To evaluate the association between physical activity changes in those aged 11 to 15 years and lung function at age 15 years.

METHODS

The original cohort comprised 5,249 hospital-born children during the calendar year of 1993 in Pelotas, Brazil. In 2004-2005 and 2008-2009, all cohort members were sought for follow-up visits. Self-reported physical activity was measured at ages 11 and 15 years. At the 2008-2009 visit, when participants were 15 years old, spirometry was performed. Linear regression was used, and all analyses were stratified by sex.

RESULTS

Of the 5,249 original members of the cohort, 4,325 were located at 15 years of age, and spirometry was performed on 4,010 members. Forced expiratory volume in 1 second was not associated with physical activity. In girls, those who were active in leisure time in both periods have better percent-predicted forced vital capacity (β = 3.573 [95% confidence interval {CI}: 1.015, 6.130]) and forced expiratory volume in the 6 seconds (β = .095 [95% CI: .021, .168]) than those who were inactive in the two periods. Also in girls, those who became active at 15 years of age had higher peak expiratory flow than those who were inactive at 11 and 15 years of age. In boys, only those who became inactive in leisure time had worse peak expiratory flow (β = -.180 [95% CI: -.339, -.021]) than boys who were inactive at ages 11 and 15 years.

CONCLUSIONS

Self-reported leisure-time physical activity was associated with better effort-dependent lung function parameters, particularly among girls.

Physical activity and exercise-induced bronchoconstriction in Greek schoolchildren

OBJECTIVE

To investigate the association between physical activity and exercise-induced bronchoconstriction (EIB) in an urban population sample of schoolchildren, taking into account potential confounders such as asthma symptoms and overweight.

METHODS

Children aged 10-12 years answered validated questionnaires on physical activity (Physical Activity and Lifestyle Questionnaire) and asthma symptoms (ISAAC questionnaire), and were categorized according to their body mass index (BMI). EIB (FEV(1) decrease from baseline ≥13%) was assessed by a standardized free running Exercise Challenge Test (ECT).

RESULTS

Six hundred seven children completed the ECT. There were no differences among asthma groups (diagnosed asthma, asthma-related symptoms not diagnosed as asthma, no asthma-related symptoms) regarding total daily energy expenditure and time spent in mild (1.1-2.9 metabolic equivalents-METs), moderate (3-6 METs), and vigorous (>6 METs) activities. Only overweight/obese EIB-positive children had shorter duration of vigorous activity as compared to their EIB-negative or non-overweight/obese EIB-positive peers. Total daily energy expenditure and duration of mild- and moderate-intensity activity were negatively associated with EIB independently of BMI status or asthma-related symptoms.

CONCLUSIONS

Decreased levels of physical activity are associated with EIB irrespectively of BMI status and asthma-related symptoms. Longitudinal studies are needed to confirm the negative impact of sedentary lifestyle on the development of EIB suggested by these findings.

High screen time is associated with asthma in overweight Manitoba youth

OBJECTIVE

Low physical activity and high sedentary behavior are associated with adverse health outcomes, including asthma. The purposes were to (1) determine if low physical activity and/or high screen time increase the risk of asthma and airway hyperresponsiveness (AHR) in youth and (2) determine if weight status modifies these associations.

METHODS

This is a prospective cohort study of healthy weight and overweight Canadian youth. In 2003-2005, 723 youth (8.6 ± 0.5 years; 34.0% asthma, 55.9% boys) were recruited from the 1995 Manitoba Prospective Cohort Study. In 2008-2010, 489 returned for follow-up measures (30.9% asthma, 56.6% boys). The primary exposure variables were parent-reported physical activity and screen time at 8-10 years of age. The primary outcome measures were pediatric allergist-defined asthma and AHR defined as the provocative concentration of methacholine required to induce a 20% fall in forced expiratory volume in 1 second (FEV(1)).

RESULTS

Low physical activity (≤2 times weekly) was not associated with asthma or AHR. However, high screen time (≥1 hour/day) was associated with a greater odds of asthma at baseline (odds ratio (OR) = 2.01, 95% confidence interval (CI) = 1.20-3.37, p < .01) and follow-up (OR = 2.11, 95% CI = 1.14-3.89, p < .02) versus low screen time. This association was more pronounced among overweight youth (baseline: OR = 3.95, 95% CI = 1.70-9.12, p < .0001; follow-up: OR = 3.22, 95% CI = 1.17-8.86, p < .02). Screen time was not associated with AHR at baseline or follow-up.

CONCLUSIONS

High screen time increases the risk of asthma, particularly among overweight youth. Screen time, in addition to physical activity, should be included in clinical assessments of youth with asthma.

"Asthma isn't an excuse, it's just a condition": youths' perceptions of physical activity and screen time

OBJECTIVE

During puberty, physical activity patterns begin to decline, while sedentary time increases. These changes may be confounded by asthma. The purpose of this study was to gain insight into youths' perceptions of screen time and physical activity by asthma status.

METHODS

Four interviews and seven focus groups with boys only or girls only were conducted with 15- to 16-year-old youth enrolled in either of two asthma-focused cohorts in Manitoba, Canada. Using a semi-structured interview guide, youth were asked about their perceptions of physical activity and screen time such as texting, watching television, electronic games, and Internet chatting and about their perceptions of the influence that asthma has on these behaviors. Data were analyzed using thematic coding.

RESULTS

Two themes were common to youth with asthma and without asthma: (1) sports are an integral part of youths' lives and (2) screen time is important to youth. Two themes were identified among youth with asthma only: (1) physical activity used to be more difficult and (2) being active and living with asthma. Youth with asthma described physical activity as neither a hindrance to activity nor an excuse for inactivity, although asthma may still present some challenges. They also acknowledged their reliance on screen time for communication and for entertainment.

CONCLUSIONS

Youth with asthma believe that physical activity has become increasingly easier as they become older and that being active with asthma, despite its challenges, is a key part of their lives.

The "other" respiratory effect of opioids: suppression of spontaneous augmented ("sigh") breaths

The purpose of this study was to examine the effects of a clinically relevant opioid on the production of augmented breaths (ABs) in unanesthetized animals breathing normal room air, using a dosage which does not depress breathing. To do this we monitored breathing noninvasively, in unrestrained animals before and after subcutaneous injection of either morphine, or a saline control. The effect of ketamine/xylazine was also studied to determine the potential effect of an alternative sedative agent. Last, the effect of naloxone was studied to determine the potential influence of endogenous opioids in regulating the normal incidence of ABs. Morphine (5 mg/kg) had no depressive effect on breathing, but completely eliminated ABs in all animals in room air (P = 0.027). However, when animals breathed hypoxic air (10% O(2)), animals did express ABs, although their incidence was still reduced by morphine (P < 0.001). This was not a result of sedation per se, as ABs continued at their normal rate in room air during sedation with ketamine. Naloxone had no effect on breathing or AB production, and so endogenous opioids are not likely involved in regulating their rate of production under normal conditions. Our results show that in unanesthetized animals breathing normal room air, a clinically relevant opioid eliminates ABs, even at a dose that does not cause respiratory depression. Despite this, hypoxia-induced stimulation of breathing can facilitate the production of ABs even with the systemic opioid present, indicating that peripheral chemoreceptor stimulation provides a potential means of overcoming the opioid-induced suppression of these respiratory events.

Allergen exposure modifies the relation of sensitization to fraction of exhaled nitric oxide levels in children at risk for allergy and asthma

BACKGROUND

Studies on airway inflammation, measured as fraction of exhaled nitric oxide (FENO), have focused on its relation to control of asthma, but the contribution of allergen exposure to the increase in FENO levels is unknown.

OBJECTIVE

We evaluated (1) whether FENO levels were increased in children with allergic sensitization or asthma; (2) whether specific allergen exposure increased FENO levels in sensitized, but not unsensitized, children; and (3) whether sedentary behavior increased FENO levels independent of allergen exposures.

METHODS

At age 12 years, in a birth cohort of children with a parental history of allergy or asthma, we measured bed dust allergen (dust mite, cat, and cockroach) by means of ELISA, specific allergic sensitization primarily based on specific IgE levels, and respiratory disease (current asthma, rhinitis, and wheeze) and hours of television viewing/video game playing by means of questionnaire. Children performed spirometric maneuvers before and after bronchodilator responses and had FENO levels measured by using electrochemical detection methods (NIOX MINO).

RESULTS

FENO levels were increased in children with current asthma (32.2 ppb), wheeze (27.0 ppb), or rhinitis (23.2 ppb) compared with subjects without these respective symptoms/diagnoses (16.4-16.6 ppb, P < .005 for all comparisons). Allergic sensitization to indoor allergens (cat, dog, and dust mite) predicted higher FENO levels and explained one third of the variability in FENO levels. FENO levels were highest in children both sensitized and exposed to dust mite. Greater than 10 hours of weekday television viewing was associated with a 0.64-log increase in FENO levels after controlling for indoor allergen exposure, body mass index, and allergic sensitization.

CONCLUSION

Allergen exposures and sedentary behavior (television viewing/video game playing) might increase airway inflammation, which was measured as the FENO.

The dynamic face of respiratory research: understanding the effect of airway disease on a lung in constant motion

The lungs are in a constant state of motion. The dynamic nature of tidal breathing, whereby cycles of pressure changes across the lungs cause the chest wall, lung tissue and airways to repeatedly expand and contract, ventilates the lung tissue and allows respiration to occur. However, these regular cycles of tidal inspirations and expirations are punctuated by breaths of differing volumes, most particularly periodic deep inspirations. In normal, healthy subjects, these deep inspirations have a dual effect in reducing airway responsiveness. Firstly, deep inspirations taken under baseline conditions protect the airways against subsequent bronchoconstriction, termed DI bronchoprotection. Secondly, deep inspirations are able to dramatically reverse bronchoconstriction. The ability for deep inspirations to reverse bronchoconstriction appears to be due to both the ability to dilate the airways with a full inspiration to total lung capacity (TLC) and the rate at which the airways re-narrow once tidal breathing is resumed. Deep inspiration reversal is reduced in subjects with asthma and is due both to a reduced ability to dilate the airways as well as an increase in the rate of re-narrowing. On the other hand, DI bronchoprotection is completely absent in asthma. Although the mechanisms behind these abnormalities remain unclear, the inability for deep inspirations to both protect against and fully reverse bronchoconstriction in patients with asthma appears critical in the development of airway hyperresponsiveness. As such, determining the pathophysiology responsible for the malfunction of deep inspirations in asthma remains critical to understanding the disease and is likely to pave the way for novel therapeutic targets.

Plethysmographic lung volumes in children with sighing dyspnea

BACKGROUND

This study compared the plethysmographic lung volumes of children with sighing dyspnea with healthy children and tested the hypothesis that sighing children suffer from hyperinflation or gas trapping as a cause of dyspnea.

METHODS

From January 2006 to December 2006, pediatric patients with sighing dyspnea presenting to the pulmonary clinic of a tertiary children's hospital who had no apparent cardiopulmonary diseases were prospectively enrolled; normal healthy children were invited to participate for comparison. Baseline pre-bronchodilator spirometry and post-inhaled bronchodilator spirometry were measured for the determination of bronchodilator response. Plethysmographic lung volumes were determined solely for total lung capacity, residual volume (RV) and functional residual capacity (FRC) without the use of inhaled bronchodilator according to standard procedure.

RESULTS

Eighteen sighing children (10 boys) and 10 healthy subjects (six boys) were included in the present study. They had a median age of 13 years (range, 8-15 years) and 13 years (range, 8-17 years), respectively. The mean baseline forced vital capacity (FVC) of subjects with dyspnea was 79.4 +/- 16.7% of predicted, while that of the normal control children was 88.4 +/- 6.7%, which was not statistically significantly different. Forced expiratory volume in 1 s (FEV(1)), FEV(1)/FVC % of predicted were within normal limits and indicated no bronchodilator response. RV and RV/total lung capacity (TLC) were elevated in children with sighing dyspnea that were not measured by spirometry, but TLC and FRC measured on plethysmography (FRC(pleth)) were not increased.

CONCLUSIONS

RV and RV/TLC were higher in children with sighing dyspnea that were not measured by spirometry, but TLC and FRC(pleth) were not increased. The causal link between dysfunctional breathing patterns and changes in static lung volumes was not able to be determined in the present study. The possibility of heterogeneity of patients with sighing dyspnea obscures the significance of lung volume discrepancy in this population; further subdivision of children with sighing dyspnea in a larger cohort of patients is required.

Wheeze and asthma in children: associations with body mass index, sports, television viewing, and diet

BACKGROUND

Obesity, physical activity, and dietary habits are distinct but strongly interrelated lifestyle factors that may be relevant to the prevalence of wheeze and asthma in children. Our goal was to analyze the relationship of body mass index (BMI), regular sports participation, TV viewing, and diet with current wheezing and asthma.

METHODS

We investigated 20,016 children, aged 6-7 years, who were enrolled in a population-based study. Parents completed standardized questionnaires. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs), while adjusting for several confounders and simultaneously considering BMI, regular sports activity, TV viewing and selected dietary items.

RESULTS

A total of 1575 children (7.9%) reported current wheezing and 1343 (6.7%) reported current asthma. In a multivariate model, an elevated BMI was associated with wheeze and current asthma: children from the highest quintile (compared with the lowest quintile) had an increased risk of wheeze (OR = 1.47; CI = 1.20-1.82) or current asthma (1.61; 1.28-2.01). Wheeze or asthma was not associated with regular sports activity. Subjects who spent 5 or more hours per day watching television were more likely to experience wheeze (1.53; 1.08-2.17) or current asthma (1.51; 1.04-2.2) compared with those who viewed TV less than 1 hour a day. Adding salt to food was strongly and independently associated with current wheeze (2.58; 1.41-4.71) and current asthma (2.68; 1.41-5.09).

CONCLUSIONS

Our data support the hypothesis that high body weight, spending a lot of time watching television, and a salty diet each independently increase the risk of asthma symptoms in children.

Physical activity and bronchial hyperresponsiveness: European Community Respiratory Health Survey II

BACKGROUND

Identification of the risk factors for bronchial hyperresponsiveness (BHR) would increase the understanding of the causes of asthma. The relationship between physical activity and BHR in men and women aged 28.0-56.5 years randomly selected from 24 centres in 11 countries participating in the European Community Respiratory Health Survey II was investigated.

METHODS

5158 subjects answered questionnaires about physical activity and performed BHR tests. Participants were asked about the frequency and duration of usual weekly exercise resulting in breathlessness or sweating. BHR was defined as a decrease in forced expiratory volume in 1 s of at least 20% of its post-saline value for a maximum methacholine dose of 2 mg.

RESULTS

Both frequency and duration of physical activity were inversely related to BHR. The prevalence of BHR in subjects exercising or=4 times a week was 14.5%, 11.6% and 10.9%, respectively (p<0.001). The corresponding odds ratios were 1.00, 0.78 (95% CI 0.62 to 0.99) and 0.69 (95% CI 0.50 to 0.94) after controlling for potential confounding factors. The frequency of BHR in subjects exercising <1 h, 1-3 h and >or=4 h a week was 15.9%, 10.9% and 10.7%, respectively (p<0.001). The corresponding adjusted odds ratios were 1.00, 0.70 (95% CI 0.57 to 0.87) and 0.67 (95% CI 0.50 to 0.90). Physical activity was associated with BHR in all studied subgroups.

CONCLUSIONS

These results suggest that BHR is strongly and independently associated with decreased physical activity. Further studies are needed to determine the mechanisms underlying this association.

Influence of physical inactivity on the prevalence of hay fever

BACKGROUND

Atopic diseases constitute a major public health problem, increasing constantly in frequency and severity. While treatments are improving, the main cause for an increasing trend of hay fever and its definite triggers remain unclear. The aim of our study was to assess whether physical inactivity could be a risk factor for hay fever.

METHODS

We analysed data of a cohort of children aged 5-14 years at baseline (1992-1993) who were followed up until 2003-2005. Parental-reported information on physical activity (being active, doing sports) was obtained for 2429 children participating at the baseline survey (active: n = 1923; semi-active: n = 364; inactive: n = 142). A total of 1703 children (70.1%) were reapproached at least once during follow-up. Logistic regression models were applied to study associations between hay fever, allergic sensitization and physical activity, adjusted for potentially relevant confounders such as age, gender, study site, parental education, breastfeeding, crowding, daycare, dampness or visible moulds, contact to cats, current or prior environmental tobacco smoke exposure and parental atopy.

RESULTS

Significantly higher rates of hay fever were seen for inactive children [aOR 2.39 (95% CI 1.31-4.36) for baseline survey 1992-1993 and aOR 1.76 (95% CI 1.14-2.71) for the follow-up-period until 2005]. In addition, the relative risk of incident cases of hay fever increased depending on inactivity [aRR 1.50 (95% CI 1.05-2.13)]. No association was found between physical inactivity and allergic sensitization assessed by radioallergosorbent test determinations.

CONCLUSIONS

Although the underlying biological mechanisms could not be clarified, increasing physical activity in childhood is suggested to prevent hay fever.

[Physical fitness in children with asthma]

The exercise limitation in a child with asthma is the result of several factors: the lack of ventilatory reserve, muscle deconditioning, and cardiac limitation. The severity of the airway obstruction is a major determinant of physical fitness. Aerobic and anaerobic fitness are equally affected. Both types of fitness can be improved by specific training programs.

Asthma severity and prevalence: an ongoing interaction between exposure, hygiene, and lifestyle

Why are the prevalence and severity of asthma increasing? Platts-Mills looks at the key studies that can help to anwer this important question