Biomedical subjects

D Sherrill

Publications and source records attributed to D Sherrill.

18 recordsLinked to original sources

PubMed1999

Respiratory syncytial virus in early life and risk of wheeze and allergy by age 13 years.

BACKGROUND: The relation between lower respiratory tract illnesses in early life caused by the respiratory syncytial virus (RSV) and the subsequent development of wheezing and atopy in childhood is not well understood. We studied this relation in children who had lower respiratory tract illnesses that occurred before 3 years of age. METHODS: Children were enrolled at birth and cases of lower respiratory tract illness were ascertained by a physician. Viral tests were done for specimens collected at the time of the illness. Children were classified into five groups according to type and cause of lower respiratory tract illness. Children were then followed prospectively up to age 13, and we measured frequency of wheezing, pulmonary function, and atopic status (allergy skin-prick tests, serum IgE concentrations). FINDINGS: RSV lower respiratory tract illnesses were associated with an increased risk of infrequent wheeze (odds ratio 3.2 [95% CI 2.0-5.0], p < 0.001), and an increased risk of frequent wheeze (4.3 [2.2-8.7], p < or = 0.001) by age 6. Risk decreased markedly with age and was not significant by age 13. There was no association between RSV lower respiratory tract illnesses and subsequent atopic status. RSV lower respiratory tract illnesses were associated with significantly lower measurements of forced expiratory volume (2.11 [2.05-2.15], p < or = 0.001) when compared with those of children with no lower respiratory tract illnesses, but there was no difference in forced expiratory volume after inhalation of salbutamol. INTERPRETATION: RSV lower respiratory tract illnesses in early childhood are an independent risk factor for the subsequent development of wheezing up to age 11 years but not at age 13. This association is not caused by an increased risk of allergic sensitisation.

Adolescent↗

PubMed1999

Influence of parental smoking on respiratory symptoms during the first decade of life: the Tucson Children's Respiratory Study.

Compelling evidence suggests a causal relation between exposure to parental cigarette smoking and respiratory symptoms during childhood. Still, the roles of prenatal versus postnatal parental smoking need clarification. In this study, the authors assessed the effects of passive smoking on respiratory symptoms in a cohort of over 1,000 children born during 1980-1984. The children were enrolled in the Tucson Children's Respiratory Study in Tucson, Arizona, and were followed from birth to age 11 years. The population was generally middle class and consisted of two main ethnic groups, non-Hispanic Whites (75%) and Hispanics (20%), reflecting Tucson's population. Information on parental smoking and on wheeze and cough in their children was elicited from parents by using questionnaires at five different surveys. Data were analyzed both cross-sectionally and by using the generalized estimation equation approach, a longitudinal mixed-effects model. The best-fitting model indicated that maternal prenatal but not postnatal smoking was associated with current wheeze (odds ratio = 2.3, 95% confidence interval 1.4-3.8) independently of a family history of asthma, socioeconomic factors, and birth weight. This effect was time dependent and significant only below age 3 years; although independent of gender, the association was stronger for girls (odds ratio = 3.6, 95% confidence interval 1.6-8.0). Cough was not associated with parental smoking during the first decade of life. This transitory effect of maternal prenatal smoking on wheezing could be due to changes that affect the early stages of lung development.

Adult↗

PubMed1999

Breast-feeding, maternal IgE, and total serum IgE in childhood.

BACKGROUND: There is controversy regarding the relationship of the effect of breast-feeding on markers of allergy such as total serum IgE in childhood. OBJECTIVE: This study, using longitudinal data, tested the hypothesis that the relation of breast-feeding to IgE in childhood differs depending on maternal total IgE level. METHODS: Total serum IgE was assessed with the paper radioimmunosorbent test at 4 ages in nonselected children enrolled at birth into the prospective Tucson Children's Respiratory Study. Children were classified as never breast-fed, breast-fed less than 4 months, or breast-fed 4 months or longer, on the basis of physician report or questionnaires completed by parents by the time the child was 18 months old. A longitudinal random effects model was used to test for group differences and temporal trends in IgE for children classified with reference to maternal IgE (high tertile vs all others) and breast-feeding history. A total of 664 children with 1457 observations were included. RESULTS: Among children whose mothers were in the 2 lower tertiles of IgE, breast-feeding was associated with lower total serum IgE at age 6 years (24.2 vs 44.3 IU/mL for never breast-fed children; P <.02); similar trends existed at age 11 years. In contrast, for children whose mothers were in the highest tertile of IgE, breast-feeding of 4 months or longer was associated with higher IgE levels in the child compared with those never breast-fed or breast-fed less than 4 months (97.0 vs 38.9 IU/mL; P <. 005). These cross-sectional analyses were confirmed with the longitudinal random effects model, which also showed no effect of confounders. Paternal IgE showed no similar relation with child IgE. CONCLUSION: Breast-feeding appears to have paradoxic relations with IgE in childhood, depending on maternal IgE level. These findings may help explain the contradictory results found in other investigations of the relation of breast-feeding to allergic symptoms and markers.

Breast Feeding↗

PubMed1999

On early sensitization to allergens and development of respiratory symptoms.

BACKGROUND: Various studies have suggested that a sequence of events occurring in childhood may affect the development of asthma in susceptible individuals. We have investigated whether early childhood sensitization to aeroallergens is an important risk factor in the later development of asthma symptoms. OBJECTIVE AND METHODS: In this study we examine this issue in children enrolled in the Tucson epidemiology study of obstructive airways disease, who had at least two allergen skin tests, one before and one after 8 years of age. Respiratory symptom data were available from 12 survey questionnaires, spanning a period of 20 years. During the first, sixth, seventh and eleventh surveys, skin tests were performed with commercially available allergens. CONCLUSION: As compared with children who were sensitized after 8 years of age, children over 8 years who were sensitized to any allergen before age 8 years were significantly more likely to report shortness of breath with wheeze (SOBWZ), wheeze apart from colds or wheeze most days (OR = 4.1 SOBWZ; OR = 3.88 WZ apart from colds; and OR = 2.83 WZ most days). Children who were sensitized after 8 years were no more likely to have the symptoms described above than children who were never found to be sensitized. Based on these results we conclude that early allergic sensitization is a significant risk factor for later development of wheezy symptoms, where as late sensitization is not.

Adolescent↗

PubMed1998

Statistical methods. Childhood asthma.

Statistical methods that are applied to trials of early or prophylactic interventions in childhood asthma may differ in important respects from those currently used for therapeutic trials in established asthma, which typically involve randomization of individuals and measurement of within-individual changes in continuous measures of disease severity. Randomization of small numbers of larger units (e.g., health centres) is less effective for controlling confounding than randomization of individuals. Because early interventions are by definition targeted at healthy children or those with mild disease, outcomes cannot usually be assessed as within-subject changes, but are analysed as between-subject comparisons of traits, states or events. Methods derived from observational epidemiology, including multiple regression, logistic regression and proportional hazards regression, are appropriate here. When there are repeated measures of outcome (such as lung function monitored at intervals through childhood), random effects models or mixed longitudinal models may be used. Calculations of sample size need to take into account the proposed form of randomization and analysis, and also the efficacy of the intervention and degree of compliance. Multiple end-points should be ranked for importance at the start of a trial and greater weight attached to significant results for primary outcomes.

Anti-Asthmatic Agents↗

PubMed1996

On modeling longitudinal pulmonary function data.

In this paper we have discussed how random effects can be included in linear models to accommodate the analyses of longitudinal pulmonary function (REM) and categorical (GEE) types of respiratory data. It was suggested that REM analysis be used for continuous observations that are normally distributed or that can be transformed to have near normal distributions and that GEE be used for categorical or non-normally distributed data. Two methods were reviewed, parallel plots and within-subject regression fitting, which can assist in determining the order of random effects to be included. Using a sample data set of longitudinal FEV1 measures, we outlined the steps that should be taken for selecting the within-subject error structure, the order of random effects, elements of the between-subject covariance matrix, and selecting the most important or predictive fixed effects. Lastly, two different types of residual plots were illustrated, conditional and marginal, which can be used to detect outliers and possible trends from underfitting the observed data. All options discussed herein are not available in all the programs currently available for doing the REM and GEE modeling.

Computer Simulation↗

PubMed1995

The effect of size and age of subject on airway responsiveness in children.

Methodologies used to assess airway responsiveness (AR) in children administer the same dosage schedule to all children despite the great range in the size of subjects. The aim of this study was to examine the hypothesis that the level of AR is size dependent within same-age cohorts and between different ages. Among a birth cohort of 1,037 New Zealand children participating in a longitudinal study, 818 had at least two measurements of airway responsiveness between ages 9 and 15 yr. Each child performed spirometry and a four-dose methacholine inhalation test. A continuous slope index of methacholine responsiveness was computed. AR slope indexes were analyzed using longitudinal methods, which included an indicator variable for subjects who reported having any wheeze. AR was lowest in both males and females in the upper quartile for height than those in the lower quartile, independently of age. AR tended to be higher (responded to lower concentrations of methacholine) in boys than girls and to decline with age among wheezers. The greater level of responsiveness in smaller or younger children could be explained by these individuals having received a dose of methacholine that was relatively large for their size.

Adolescent↗

PubMed1992

Effects of passive smoking on lung growth in children.

The objective of this study was to determine the effects of passive smoking on functional lung growth in children and adolescents. It was hypothesized that passive smoking might reduce lung function growth, especially in susceptible children. The assumption was that those most susceptible would be children who started with low lung function, as it had been shown that they had slower growth of lung function, and start to decline earlier. There were 138 non-Hispanic Caucasian children and adolescents, ages 5 through 15, who had at least three satisfactory longitudinal lung function tests over a 13 year period in the Tucson epidemiological study of airway obstructive diseases. Those who started in childhood with normal function did not show any effect of passive smoking, nor did females who started with low lung function. Males starting with low lung function whose parents smoked showed definite changes. Their forced expiratory volume in 1 second (FEV1) grew even more slowly between ages 13 through 16, related primarily to continuous parental smoking. They also had higher rates of decline for FEV1 to forced vital capacity (FVC) ratio and maximum flow at 50% vital capacity to FVC ratios than either the low function group without passive smoking or the normal function groups. This was independent of any symptoms or diagnoses present in this male low function group.

Adolescent↗

PubMed1992

The effects of airway hyperresponsiveness, wheezing, and atopy on longitudinal pulmonary function in children: a 6-year follow-up study.

We examined growth of spirometric lung function in 696 children of European ancestry who were followed from ages 9 to 15 years and stratified according to their degree of responsiveness to methacholine inhalation challenge, atopic status, and respiratory symptoms. Subjects were participants in the longitudinal Multidisciplinary Health and Development Study in Dunedin, New Zealand. Forced expired volume in 1 second (FEV1), and vital capacity (VC) were measured at 9, 11, 13, and 15 years of age, concurrently with assessment of airway responsiveness determined by the concentration of methacholine causing a 20% fall in FEV1 (PC20 FEV1). Atopic status was assessed at age 13 by skin-prick testing to 11 allergens. In children demonstrating airway hyperresponsiveness, FEV1 increased with age at a slower rate, and the FEV1/VC ratio had a faster rate of decline through childhood, compared to non-responsive children. Subjects with positive skin tests to house dust mite and cat dander also had lower mean FEV1/VC ratios than the control group. Any reported wheezing was associated with slower growth of FEV1 and VC in males. We conclude that in New Zealand children with airway responsiveness and/or atopy to house dust mite or cat growth of spirometric lung function is impaired.

Adolescent↗

PubMed1992

Antigen enhances neuronally induced contraction of intrapulmonary bronchi from IgE-producing rabbits.

The effect of in vitro antigen exposure on contraction induced by electrical field stimulation (EFS) was examined in bronchial rings isolated from rabbits producing specific IgE antibodies. After exposure to antigen, tissues showed an enhanced isometric contractile response to EFS especially at low frequencies, leading to a significant change in the mean slope factor (p less than 0.05) derived from modeling the log frequency response curve using a 4-parameter logistic function. Also, the mean log EF20 +/- SEM decreased from 1.03 +/- 0.05 to 0.88 +/- 0.07 Hz (p less than 0.02). This antigen-induced effect was blocked by pretreatment with 3 microM chlorpheniramine and not observed in unsensitized tissues. Antigen challenge of tissues passively sensitized with IgE (but not IgG) antibodies led to a similar EFS-enhancing effect, significantly reducing the mean slope factor (p less than 0.025). Substituting EFS with exogenous acetylcholine resulted in no antigen-induced enhancement of contraction. The data suggest that antigen-IgE interaction leads to local histamine release sufficient to enhance the function of excitatory airway neurons.

Animals↗

PubMed1990

Differential rates of lung growth as measured longitudinally by pulmonary function in children and adolescents.

A sample population of 67 males and 71 females with longitudinal lung function and other anthropometric measurements from all non-Hispanic white children in the Tucson Epidemiological Study of Airway Obstructive Diseases (AOD) was studied to evaluate biological determinants of the rate of lung growth. Groups within gender were defined by the following factors: 1) maximum height, 2) age at maximum forced expiratory volume at 1 second (FEV1), 3) % predicted initial FEV1 or FEV1/FVC ratio. Only groups defined by low initial function (FEV1 or FEV1/FVC less than or equal to 85% predicted versus greater than 85% predicted) showed statistically significant differences from those with more "normal" function by comparing their maximum % of predicted FEV1s and FEV1/FVC ratios. The longitudinal FEV1 data by age for the latter groups were characterized by a mathematical model (polynomial smoothing spline) yielding optimal fitted curves and an estimate of each group's growth velocity curve. The statistical comparisons between these fitted curves indicate that subjects with low initial pulmonary function continued to have significantly lower FEV1 values for males older than 13.12 years and for females between 8.23 and 15.3 years. At post-hoc analysis persistent wheezing was more likely in the initially more impaired group. Disease at the end of follow-up was not related to initial functional status.

Adolescent↗

PubMed1981

Humidity and temperature changes during low flow and closed system anaesthesia.

Water humidity and temperature were measured in the proximal end of the inspiratory limb in anaesthetic circuits used to anaesthetize three groups of adult patietnts using various fresh gas flows (FGF). Humidity increased as FGF's were lowered, with 98% water humidification achieved when FGF's of less than 0.51/min were administered. Temperature at the same site changed about 1-2.5 degrees C in inverse proportion to the volume of FGF. This advantage of closed system and low flow anaesthesia is a further reason for their wide-spread utilization.

Adult↗

PubMed1980