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Biomedical subjects

M R Becklake

Publications and source records attributed to M R Becklake.

At least 19 recordsLinked to original sources
PubMed1992

The mineral dust diseases.

The mineral dust diseases, also called the pneumoconioses, comprise a wide spectrum of conditions ranging from diseases characterized by diffuse collagenous pulmonary reactions to relatively small lung burdens of bioactive dusts (e.g. silicosis, asbestosis) to diseases characterized by largely non-collagenous reactions in the face of heavy lung dust burdens (e.g. coal workers pneumoconiosis). According to information submitted to the International Labour Office, which is however incomplete, substantial numbers of individuals are still at risk for the mineral dust diseases in the workplaces of the world. An overview of their epidemiology in industrialized and industrializing countries reveals more commonalities than contrasts. Commonalities include the major determinants of disease (including exposure level, intensity and particle size distribution), their clinical manifestations and, probably, secular trends towards less clinically severe disease, at least in the larger, better controlled workplaces. Still a risk however, in both industrializing as well as industrialized countries, are the small, uncontrolled workplaces, often the source of mini-epidemics. Contrasts relate to the incidence and/or prevalence rates of tuberculosis amongst workforces at risk for the mineral dust diseases. Rates, which are invariably higher in industrializing than in industrialized economies, usually reflect the background tuberculosis rates in the populations which furnish the industrial workforces and they should be the target for control measures. Research in the industrialized countries should focus on disease mechanisms and on the bioactivity of workplace contaminants, old and new, and in the industrializing countries on the distribution and determinants of mineral dust diseases in their workplaces.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1992

Spirometric lung function. Distribution and determinants of test failure in a young adult population.

Spirometric test failure has been defined as failure by a subject to meet the acceptability and/or reproducibility criteria laid down by the American Thoracic Society for measurements derived from forced expiratory maneuvers. The prevalence and determinants of spirometric test failure were examined in 416 men and women aged 20 to 45 yr working in an office environment. In this study population, 11.5% (28 men and 20 women) exhibited test failure for forced expiratory volume in one second (FEV1). The main determinant of test failure in men was bronchial hyperresponsiveness to methacholine challenge (odds ratio 6.7; confidence interval 1.7, 27.1) and in women being a current smoker (odds ratio 4.02; confidence interval 1.13, 14.33). There was also a relationship to eczema in both men and women, but not at a statistically significant level. When FEV1 variability was defined as the difference (in milliliters) between the two best FEV1 values and the results of men and women combined for analysis, significant predictors were a history of eczema, recurrent chest illness in the past 3 yr, and level of bronchial responsiveness to inhaled methacholine. These findings contribute to the gathering evidence that test failure may be of itself an indicator of impaired respiratory health, and its association with bronchial hyperresponsiveness to methacholine in men suggests that in them test failure is related to airway lability, but in women the relationship to smoking suggests an irritative mechanism.

Adolescent↗
PubMed1991

Effect of cigarette smoking on evolution of ventilatory lung function in young adults: an eight year longitudinal study.

BACKGROUND: There are few data on the quantitative effects of cigarette smoking on lung function in young adults. These effects are important in the understanding of the early stages of chronic airflow obstruction. METHODS: A longitudinal study over eight years was carried out to estimate quantitatively the effect of cigarette smoking on ventilatory lung function in young adults and to examine the possibility that the effect is modified by other factors. The study population were 15 to 40 years of age at initial examination, when they underwent spirometry and completed an interviewer administered questionnaire on respiratory health. Eight years later 391 of the subjects were re-examined (38% response rate). The quantitative effect of cigarette smoking during the study period on the average change of forced expiratory volume in one second (FEV1) over time (delta FEV1) was estimated in two linear regression models that included potential confounders and other determinants of outcome. RESULTS: The first model showed a significant dose-response relation between the average rate of smoking during the study period and delta FEV1, giving an estimate of annual change in FEV1 of -0.42 ml for each cigarette smoked per day (-8.4 ml for each pack) (p = 0.04). In the second model, which took smoking before the study period as a potential confounder, the effect of smoking during the study period was slightly smaller (-0.33 ml/year for each cigarette smoked per day). This indicated that smoking before the study period had a marginal latent effect on delta FEV1 during the study. However, neither the effect of smoking before the study nor that of smoking during the study was significant, presumably because of collinearity. Interactions between cigarette smoking and gender, wheezing, atopy, and exposure to environmental tobacco smoke during the growth period were not significant with respect to their effect on the relation between cigarette smoking and delta FEV1. CONCLUSION: Cigarette smoking has a dose related adverse effect on the evolution of ventilatory lung function in young adulthood.

Adolescent↗
PubMed1991

Effect of standing versus sitting position on spirometric indices in healthy subjects.

This study examined the effect of the standing versus the sitting position on spirometric indices in 94 healthy non-obese adult subjects (41 men and 53 women) with the order of testing randomised. On average all the spirometric indices examined, except the peak expiratory flow rate, were higher in the standing compared to the sitting position although the change was only significant at the 5% level for FEV1 in women. The fall in FEV1 with the change in position was statistically related to the ponderal index but not to age, height or the initial lung function level. A uniform posture for spirometry is recommended in epidemiological studies examining longitudinal trends in lung function, as well as in cross-sectional aetiological studies examining, for instance, the effects of environmental and/or occupational exposures. A uniform posture is also recommended for clinical studies which involve repeated measurements over time, for instance to measure the effect of treatment or the natural history of airways disease.

Adult↗
PubMed1991

Ventilatory lung function in young cigarette smokers: a study of susceptibility.

The objective of this study was to estimate the effect of cigarette smoking on ventilatory lung function among young adults with special emphasis on the recognition of susceptible subgroups. In a cross-sectional study of 1,044 adults aged 15-40 yrs, a statistically significant linear relationship between quantity of smoking in cigarette-years and level of forced expiratory volume in one second (FEV1) was found. Among current cigarette smokers, FEV1 level was on average 35 ml lower for each 100 cigarette-years of exposure (corresponding to smoking of ten cigarettes per day for 10 yrs) compared to lifelong nonsmokers in a linear regression adjusted for confounding. Potentially susceptible subgroups were studied by introducing interaction terms between quantitative smoking and gender, wheezing, atopy, asthma, childhood respiratory illness and exposure to environmental tobacco smoke during the growth period, to the additive linear regression model explaining the FEV1 level. Wheezing was found to modify the effect of smoking significantly: the FEV1 level was on average 68 ml lower for each 100 cigarette-years due to interaction between smoking and wheezing. An introduction of the interaction term eliminated the independent effect of smoking. The results suggest that the detrimental effect of smoking on FEV1 in young adults may be limited to individuals with wheezing. Thus, the presence of wheezing among smokers indicates a higher risk for low level of ventilatory lung function compared to smokers who do not wheeze.

Adolescent↗
PubMed1990

Respiratory health status of children in the eastern Transvaal highveld.

A study was undertaken to determine if there were detectable effects on the respiratory health status of children resident in the eastern Transvaal highveld as a consequence of their exposure to community air pollution, comparing them with children in areas ostensibly less polluted. A prevalence study was conducted in white schoolchildren from 11 schools in the eastern Transvaal highveld (1,031 children) and from 11 schools in non-polluted towns in the Transvaal (978 children). A questionnaire was completed by each child's mother, and height and weight were measured and spirometry recorded on a vitalograph. Cough, wheeze, asthma and chest illnesses were more frequently reported from polluted areas compared with non-polluted areas, taking into account parental smoking and home cooking fuel (odds ratios 1.34, 1.20, 1.15 and 1.88, respectively). After correcting for age, children in the polluted area were 0.83 cm shorter (P = 0.035). However, there were no significant differences in forced vital capacity and forced expiratory volume in 1 second after standardising for height, age, parental smoking and home cooking fuel. We conclude that, in children, exposure to pollution in the eastern Transvaal highveld may cause respiratory symptoms and chest illness and may affect height but does not measurably affect lung function, as assessed by spirometry.

Air Pollution↗
PubMed1990

The 'healthy smoker': a phenomenon of health selection?

The detrimental effects of smoking on lung function have been recognized for several decades. Evidence comes from cross-sectional studies which emphasize that damage, certainly at the level of the small airways, may be detectable after a relatively short smoking history, and from longitudinal studies which show that smoking is associated with an increased rate of function loss over time. Implicit in most published evaluations of the evidence has been the concept that smoking is a habit taken up at random by the general population, and that those who do and do not take up the habit start out with similar levels of lung function. Published material was reviewed for evidence to the contrary, consistent with a health selection process similar to that shown in relation to workplace exposures and labeled the 'healthy worker' effect. Despite the wealth of published data on the topic of lung function in relation to the smoking habit, much is presented in a way which does not permit the concept of the 'healthy smoker' to be addressed. Nevertheless, this review revealed sufficient evidence from cross-sectional studies, as well as evidence from one longitudinal study to support the concept of the 'healthy smoker' as an individual who takes up the habit because his/her lungs are relatively resistant to the effects of smoking. If correct, this means that previous studies, particularly those which were cross-sectional in design and focussed on younger persons, are likely to have underestimated the consequences of smoking on lung function. The concept of the 'healthy smoker' may also throw light on characteristics which identify the 'susceptible smoker'.

Adolescent↗
PubMed1990

The relationship between respiratory impairment and asbestos-related pleural abnormality in an active work force.

With the general improvement in environmental controls in workplaces where asbestos is used, an increasing number of workers are seen who exhibit isolated pleural plaques. The question as to whether these are associated with respiratory impairment independently of parenchymal disease remains unresolved. The question was reinvestigated using quantitative gallium-67 lung scanning to take into account early parenchymal change not evident on the chest radiograph. We carried out a cross-sectional study of 110 construction insulators all currently at work. Overall, 58.2% had pleural abnormality, 52.5% pleural plaques only, and 5.5% diffuse pleural thickening as assessed from the PA chest radiograph. Compared with those without, those with any pleural abnormality had a decrease in FEV1 and FVC on average of 222 and 402 ml (p less than 0.05), and those with isolated pleural plaques, a decrease on average of 200 and 350 ml (p less than 0.05), after taking into account age, height, smoking status, and the presence of parenchymal abnormality as assessed by chest radiography and gallium uptake. The complaint of dyspnea with strenuous activities was also significantly related to the width and extent of chest wall pleural thickening (p less than 0.05), independently of parenchymal disease. This study suggests that the most common radiographic findings in asbestos-exposed, isolated pleural plaques are associated with a significant reduction in FEV1 and FVC, which cannot be attributed to the presence of radiographic and subradiographic pulmonary fibrosis.

Adult↗
PubMed1989

Mesothelioma in South Africa, 1976-84: incidence and case characteristics.

Malignant mesothelioma is a rare tumour known to be associated with prior exposure to asbestos. Previous studies have described the occupational and clinical features of cases of mesothelioma in the Republic of South Africa (RSA) but none has set out to determine incidence of this disease. To estimate incidence, a case register was compiled for 1976-84 by contacting all medical practitioners and institutions likely to have seen cases of mesothelioma in this period; demographic, diagnostic and exposure details were sought. Cases were accepted if they provided evidence of histological diagnosis of mesothelioma. Fifty-two per cent of 1347 cases identified were in whites, 31% in blacks, 16% in coloureds and 1% in Asians. Seventy-three per cent of cases occurred in males. The majority of whites were aged 51-70 years, while the majority in other race groups were aged 41-60 years. The ratio of only pleural to only peritoneal mesothelioma was 11:1, although there were marked differences by race. Eighty-five per cent of males with exposure information available had prior exposure to asbestos, mostly occupational. A similar proportion of women had contact with asbestos but mostly through other types of exposure. Standardized incidence rates per million population aged 15 years and over were calculated for sex-race subgroups and were highest in white males (32.9 per million per year, 95% Cl 22.7-46.4), coloured males (24.8 per million per year, 95% Cl 16.2-36.9) and coloured females (13.9 per million per year, 95% Cl 7.7-23.5). These incidence rates are amongst the highest ever reported for a national population. Age-specific standardized incidence rates were highest in white males (over 100 per million per year in men over 55 years). Reasons for the differing rates by population group are likely to include differential access to health services. More rigorous control of asbestos exposure in the RSA is recommended.

Aged↗
PubMed1989

Relation of airway responsiveness to duration of work in a dusty environment.

Health selection within a workforce has been found in several industries and appears to be more pronounced in dustier occupations. In this study of airway disease among workers exposed to asbestos and man made mineral fibres, 215 of 246 construction insulators 50 years old or less and currently working in the Montreal area were examined. Spirometry was completed successfully in 214 workers without known asbestosis and 207 underwent methacholine bronchoprovocation testing. Airway responsiveness was expressed as PC15, the concentration of methacholine causing a 15% fall in the forced expiratory volume in one second (FEV1). Exposure to asbestos and synthetic mineral fibre dust was estimated from the total hours of work in the trade since first employment. After the effect of age, height, and pack years of smoking had been taken into account, no relation was found between hours of work and any indices obtained from the forced expiratory manoeuvre (FEV1/FVC, MMF). After the effect of airway calibre (FEV1/FVC), age, and pack years of cigarette consumption had been taken into account, airway responsiveness decreased as the total hours of work in the trade increased. These findings suggest that workers with greater levels of airway responsiveness are more sensitive to exposure in a dusty workplace and in consequence are less likely to continue. In studies of workforces a survivor effect of this nature will tend to weaken the relation between lung function abnormality and occupational exposure.

Adult↗
PubMed1989

Pulmonary tuberculosis in South African gold miners.

In 1977, a comprehensive tuberculosis management program was introduced at a medical facility which then served approximately 65,000 black gold miners. The effectiveness of this program was evaluated from the relapse rate after treatment in 2,776 men. Post-treatment follow-up averaged 23.5 months. Limited information on potential determinants of relapse was available for all subjects and more detailed information for subsets. The drug regimen was the major determinant of relapse. Age was not a determinant of relapse nor was primary resistance of Mycobacterium tuberculosis to antituberculosis drugs, which was infrequent. The initial extent and severity of disease had a direct relation with the risk of relapse. The risk of relapse was greatest during the first 3 yr after treatment but persisted for the duration of the observation period. Neither continued exposure to mine dust nor the presence of pre-existing silicosis were shown to be determinants of relapse. A 4.5-month, four-drug weekday regimen was identified as being particularly effective in this working population and may be suitable for use in other working populations in the developing world.

Actuarial Analysis↗
PubMed1989

Occupational exposures: evidence for a causal association with chronic obstructive pulmonary disease.

The increase in morbidity and mortality attributable to chronic obstructive pulmonary disease (COPD) has focused attention on environmental and host factors causally associated with the clinical entities included under the rubric of this term with a view to early preventive intervention. Despite the biologic plausibility of inhaled agents being causally implicated, only the role of tobacco smoke has been accepted beyond doubt. However, evidence implicating occupational exposures has accumulated, in particular over the last 2 yr, from: (1) community-based studies (in which larger study populations provide greater power than the usually smaller workforce based studies); (2) longitudinal studies of lung function (which enhance the signal of interest, namely the effects of the occupational exposures, and diminish the noise due to between-individual differences); (3) pathology studies (in which the outcome of interest is the quantitative measurement of emphysema), and (4) cohort mortality studies of all or specific causes of death. This evidence, reviewed here according to accepted criteria for establishing causality, leaves little doubt that occupational exposure to dust and/or to dust and fumes may be causally implicated in the genesis of COPD. As with tobacco exposure, both bronchitis (mucus hypersecretion) and airflow limitation are recognized as causally related to exposure, but not necessarily to each other. As with tobacco exposure, though effects are in general dose related to exposure, there is evidence for individual susceptibility. As with tobacco exposure, a possible host factor is the reactivity of airways to inhaled materials.(ABSTRACT TRUNCATED AT 250 WORDS)

Cohort Studies↗