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Biomedical subjects

J H Ware

Publications and source records attributed to J H Ware.

At least 73 records · Page 4Linked to original sources
PubMed1987

Occupational exposures and chronic respiratory symptoms. A population-based study.

Data from a random sample of 8,515 white adults residing in 6 cities in the eastern and midwestern United States were used to examine the relationships between occupational exposures to dust or to gases and fumes and chronic respiratory symptoms; 31% of the population had a history of occupational dust exposure and 30% reported exposure to gas or fumes. After adjusting for smoking habits, age, gender, and city of residence, subjects with either occupational exposure had significantly elevated prevalences of chronic cough, chronic phlegm, persistent wheeze, and breathlessness. The adjusted relative odds of chronic respiratory symptoms for subjects exposed to dust ranged from 1.32 to 1.60. Subjects with gas or fume exposure had relative odds of symptoms between 1.27 and 1.43 when compared with unexposed subjects. Occupational dust exposure was associated with a higher prevalence of chronic obstructive pulmonary disease as defined by an FEV1/FVC ratio of less than 0.6, when comparing exposed and unexposed participants (OR = 1.53, 95% Cl = 1.17-2.08). Gas or fume exposure was associated with a small, but not significant, increase in COPD prevalence. Significant trends were noted for wheeze and phlegm with increasing duration of dust exposure. Although 36% of exposed subjects reported exposure to both dust and fumes, there was no evidence of a multiplicative interaction between the effects of the individual exposures. Smoking was a significant independent predictor of symptoms, but did not appear to modify the effect of dust or fumes on symptom reporting. These data, obtained in random samples of general populations, demonstrate that chronic respiratory symptoms and disease can be independently associated with occupational exposures.

Adult↗
PubMed1987

Nutritional and socio-demographic risk indicators of malaria in children under five: a cross-sectional study in a Sudanese rural community.

This paper reports the results of a cross-sectional study of the association between nutritional, environmental and socio-demographic factors, and malaria occurrence among 445 children under 5 years of age in a Sudanese rural community. The overall frequency of malaria as defined by a history of clinical illness during the previous 2 months was 27%. Malaria occurrence was positively associated with the degree of malnutrition as assessed by weight-for-age. The age-adjusted odds ratio for mild malnutrition and history of malaria was 1.2 (95% confidence interval (CI): 0.7-2.0) and for moderate malnutrition and malaria was 2.1 (95% CI: 1.1-4.0). Malaria was less frequent among children 0-11 months of age relative to older children (OR = 0.4; 95% CI:0.2-0.7), and was inversely associated with ownership of a refrigerator (OR = 0.5; 95% CI:0.36-0.94), an indicator of socio-economic status. Indicators of crowding were the best predictors of the risk of malaria. Less malaria was observed in households with three or more rooms (OR = 0.6; 95% CI:0.37-0.98) and more malaria was observed in households with more than five people (OR = 2.5; 95% CI:1.4-4.5). Malaria was slightly, but not significantly, more frequent among boys and was associated with anaemia, which was probably an outcome of malaria in the past. These data suggest that undernutrition may increase the risk of malaria, and draw attention to the importance of socio-economic and environmental factors in relation to this disease. These relationships deserve further examination in prospective follow-up studies that are better able to evaluate the temporal relations of malnutrition and malaria.

Age Factors↗
PubMed1986

Explaining discrepancies between longitudinal and cross-sectional models.

Data from longitudinal studies may be analyzed both cross-sectionally and longitudinally. Discrepancies between estimates obtained from these analyses pose questions about the validity of cross-sectional estimates of change. In some cases these discrepancies are the result of period effects, cohort effects, or selective dropout. In others, they are the result of incomplete modeling of the process and are spurious rather than substantive. In this report, we show that when the true relation between a dependent variable and age is non-linear (e.g. quadratic), but is modeled as linear, the estimated age effect will be a function of the age distribution. In a continuous-time idealization, if the age distribution is Gaussian, the estimated age effects agree. If the age distribution is symmetric and the non-linearity is quadratic, cross-sectional and longitudinal results agree. Otherwise they do not. We illustrate these points by analysis of the relation between aging and pulmonary function in middle and old age using data from a large, prospective, longitudinal study.

Adult↗
PubMed1986

Indoor air pollution and pulmonary function growth in preadolescent children.

Results are reported from a study of the association between exposure to sidestream cigarette smoke or gas stove emissions and pulmonary function level and growth rate of 7,834 children seen at 2-5 annual visits between the ages of 6-10 years. Children whose mothers smoked one pack of cigarettes per day had levels of forced expiratory volume in one second (FEV1) at age eight that were 0.81% lower than children of nonsmoking mothers (p less than 0.0001), and FEV1 growth rates approximately 0.17% per year lower (p = 0.05). For a child of age eight with an FEV1 of 1.62 liters, this corresponds to a deficit in rate of change of FEV1 of approximately 3 ml/annum and a deficit of 13 ml at age eight. Children whose mothers smoked one pack per day had levels of forced vital capacity (FVC) at age eight that were 0.33% higher than children of nonsmokers (p = 0.12); however, their growth rates of FVC were 0.17% per year lower (p = 0.04). Because few mothers changed their smoking habits during the course of the study, it was not possible to determine whether the difference in rate of growth was due to current exposure or to an effect of prenatal and early childhood exposure on the course of development. The magnitude of the effect on FEV1 is consistent with deficits in FEV1 of up to 3% in early adult life due to childhood exposure to sidestream cigarette smoke. The importance of this relatively small effect will be evaluated further through follow-up of these children as they are exposed to other risk factors such as personal active smoking. The data provide some evidence for an association between gas stove exposure and pulmonary function level, especially at younger ages, but no evidence for an effect of gas stove exposure on growth rate.

Air Pollutants↗
PubMed1986

Effects of ambient sulfur oxides and suspended particles on respiratory health of preadolescent children.

Reported here are the results from an ongoing study of outdoor air pollution and respiratory health of children living in six cities in the eastern and midwestern United States. The study enrolled 10,106 white preadolescent children between 1974 and 1977 in 3 successive annual visits to each city. Each child received a spirometric examination, and a parent completed a standard questionnaire. Of this cohort, 8,380 children were seen for a second examination 1 yr later. An air pollution monitoring program was begun in each community at about the time of the first examination. For this report, measurements of total suspended particulates (TSP), the sulfate fraction of TSP (TSO4), and sulfur dioxide (SO2) concentrations at study-affiliated outdoor stations were combined with measurements at other public and private monitoring sites to create a record of TSP, TSO4, and SO2 concentrations in each of 9 air pollution regions during the 1-yr period preceding each examination and, for TSP, during each child's lifetime up to the time of testing. Across the 6 cities, frequency of cough was significantly associated with the average of 24-h mean concentrations of all 3 air pollutants during the year preceding the health examination (p less than 0.01). Rates of bronchitis and a composite measure of lower respiratory illness were significantly associated with average particulate concentrations (p less than 0.05). In analyses restricted to lifetime residents, these outcomes were significantly associated with measures of lifetime mean TSP concentration. Within the cities, however, temporal and spatial variation in air pollutant concentrations and illness and symptom rates were not positively associated.(ABSTRACT TRUNCATED AT 250 WORDS)

Air Pollutants↗
PubMed1985

The futility index. An approach to the cost-effective termination of randomized clinical trials.

Although the randomized clinical trial is recognized as the method of choice for evaluating therapeutic innovations, it is often enormously expensive--in some instances, as a result of the unnecessary continuation of a trial destined to conclude that an innovation is not superior to standard therapy. Although most large clinical trials in which results evolve over time are monitored for early evidence of efficacy or toxicity, trials are rarely terminated because the probability of a positive result regarding the value of the innovation has become low. This paper discusses the issues involved in the monitoring and early termination of long-term clinical trials and describes the futility index, a probabilistic basis for early termination of trials of innovative therapy when the accumulated data imply small probability of success. Utilization of the futility index in the management of clinical trials of innovations can be of value in reducing, at slight loss of power, the number of unproductive studies carried to completion, thereby creating new opportunities for more effective use of limited resources.

Clinical Trials as Topic↗
PubMed1985

Distribution of forced expiratory volume in one second and forced vital capacity in healthy, white, adult never-smokers in six U.S. cities.

As part of a longitudinal study of the respiratory health effects of air pollution, we measured the lung function of 2,454 white adults 25 to 74 yr of age who had never smoked and who reported no respiratory symptoms. These measurements were analyzed to develop a simple model for the cross-sectional dependence of pulmonary function on height, sex, and age. Both forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) can be effectively standardized for body size by dividing each pulmonary function measurement by the square of the standing height (HT2). The age-specific distribution of these standardized measurements is approximately Gaussian, with variance that is independent of age. Plots of FEV1/HT2 and FVC/HT2 against age showed a nonlinear relationship consistent with an increase in the rate of pulmonary function loss with age. On the basis of these graphic analyses, both pulmonary function measurements were fitted to a four-parameter normative model including sex and linear and quadratic terms in age as dependent variables. This model gave predictions that were very close to those from more complicated models currently in use. Predicted percentile levels were calculated for each sex and age, and shown to describe the observations well. The estimated annual change in height-standardized lung function based on the cross-sectional model was compared with the observed change between the first and second examinations of these adults 3 yr later. The observed changes were close to predicted values, except for subjects younger than 35 yr of age at their first examination. The observed change was larger for men than for women. Such simple longitudinal comparisons are subject to selection bias. In this study, subjects in the lowest quartile of FEV1/HT2 for their age and sex at the first examination had a lower probability of providing a lung function measurement 3 yr later.

Adult↗
PubMed1985

Effects of passive smoking on health of children.

Analysis of data on the effects of passive smoking obtained in preadolescent children from the Harvard Six-Cities Study demonstrates an exposure-response relationship between the number of smokers in the household and the reporting rates for doctor-diagnosed respiratory illness before age 2, history of bronchitis, wheeze most days and nights apart from colds, and a composite of symptoms defined as the lower respiratory index. Similarly, when only the amount currently smoked by the mother was used, the data indicated a relatively uniform increase in each of the reported diseases and symptoms. FEV1 was lower in children with smoking mothers compared to children of nonsmoking mothers. Rate of increases in FEV1 after adjusting for normal growth was significantly smaller in children of smoking mothers and was related also to amount smoked. Notably the effect on level of FVC was not seen and this finding, consistent in several studies, remains unexplained. Although children of smoking mothers were shorter on the average than children of nonsmoking mothers, no on-going passive smoking effect on height growth can be ascertained. All these differences are small and their medical significance remains to be defined.

Body Height↗
PubMed1984

Passive smoking and height growth of preadolescent children.

The attained height and height growth rate of 9273 children participating in a longitudinal study of the health effects of air pollutants were analysed to assess the association between passive exposure to cigarette smoke and physical growth between 6 and 11 years of age. Children were measured annually for 2 to 6 years. Each height measurement was adjusted for sex and age by the NCHS anthropometric standards. Each child's adjusted heights were then re-expressed as level of attained height and growth rate. Attained height exhibited a dose-response relationship with amount of current maternal cigarette smoking (p less than 0.001). Children whose mothers smoked ten or more cigarettes daily were approximately 0.65 cm shorter than children of non-smokers, while children whose mothers smoked between 1 and 9 cigarettes per day were 0.45 cm shorter. However, passive smoking was not correlated with the child's growth rate. Exposure to paternal smoking was not significantly associated with height, either in terms of attained level or growth rate. These results indicate that passive smoking in the 6- to 11-year-old child does not continue to affect the growth rate of height and that the observed association between attained height and maternal smoking behaviour is due to exposures in utero and/or during infancy and the preschool years.

Body Height↗
PubMed1984

Passive smoking, gas cooking, and respiratory health of children living in six cities.

As part of a longitudinal study of the respiratory health effects of indoor and outdoor air pollutants, pulmonary function, respiratory illness history, and symptom history were recorded at 2 successive annual examinations of 10,106 white children living in 6 cities in the United States. Parental education, illness history, and smoking habits also were recorded, along with the fuel used for cooking in the child's home. Maternal cigarette smoking was associated with increases of 20 to 35% in the rates of 8 respiratory illnesses and symptoms investigated, and paternal smoking was associated with smaller but still substantial increases. Illness and symptom rates were linearly related to the number of cigarettes smoked by the child's mother. Illness rates were higher for children of current smokers than for children of ex-smokers. The associations between maternal smoking status and childhood respiratory illnesses and symptoms were reduced but not eliminated by adjustment for parental illness history. Levels of forced expiratory volume in one second (FEV1) were significantly lower for children of current smokers than for children of nonsmokers at both examinations and highest for children of ex-smokers. Levels of forced vital capacity (FVC) were lower for children of nonsmokers than for children of current smokers at both examinations, but the difference was statistically significant only at the first examination. Both the increase in mean FVC and the decrease in mean FEV1 among children of current smokers were linearly related to daily cigarette consumption. None of the respiratory illnesses and symptoms studied was significantly associated with exposure to gas cooking in the child's home.(ABSTRACT TRUNCATED AT 250 WORDS)

Activities of Daily Living↗
PubMed1984

Random-effects models for serial observations with binary response.

This paper presents a general mixed model for the analysis of serial dichotomous responses provided by a panel of study participants. Each subject's serial responses are assumed to arise from a logistic model, but with regression coefficients that vary between subjects. The logistic regression parameters are assumed to be normally distributed in the population. Inference is based upon maximum likelihood estimation of fixed effects and variance components, and empirical Bayes estimation of random effects. Exact solutions are analytically and computationally infeasible, but an approximation based on the mode of the posterior distribution of the random parameters is proposed, and is implemented by means of the EM algorithm. This approximate method is compared with a simpler two-step method proposed by Korn and Whittemore (1979, Biometrics 35, 795-804), using data from a panel study of asthmatics originally described in that paper. One advantage of the estimation strategy described here is the ability to use all of the data, including that from subjects with insufficient data to permit fitting of a separate logistic regression model, as required by the Korn and Whittemore method. However, the new method is computationally intensive.

Air Pollution↗
PubMed1983

The Six-City Study: examples of problems in analysis of the data.

This paper presents some of the results from cross-sectional analyses and studies during air pollution alerts obtained as a part of the Six-City Study, a longitudinal study of the respiratory effects of air pollution. These analyses illustrate some of the limitations and uncertainties of epidemiologic studies. For example, an earlier report noted increased respiratory illness rates for children living in homes where gas was used for cooking. A later analysis did not confirm this. Reasons for this are explored by using different criteria and variables to be controlled for. The results illustrate that the strength of the association between cooking fuel and illness was sensitive to the definitions of the variables and the number of subjects and city cohorts. Similar examples are presented for illness rates for four respiratory diseases: asthma, bronchitis, illness before age 2 and illness last winter. These examples of cross-sectional analyses emphasize the ambiguities of studies of possible health effects of air pollution exposures close to the present ambient air quality standards.

Air Pollution↗