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Biomedical subjects

M R Becklake

Publications and source records attributed to M R Becklake.

At least 37 records · Page 2Linked to original sources
PubMed1996

Relationship between chronic dyspnea and expiratory flow limitation in patients with chronic obstructive pulmonary disease.

The purpose of this study was to assess whether expiratory flow limitation (FL), as measured by applying negative pressure at the mouth during tidal expiration, is a better predictor of dyspnea than routine spirometry measurements. The study population consisted of 117 ambulatory patients with COPD. Dyspnea was assessed according to the ATS-DLD respiratory Questionnaire. Expiratory flow limitation was measured in supine and sitting positions, and expressed as a percentage of the expired control tidal volume affected by flow limitation (FL, % VT). Using Spearman's rank correlation (rs), we found that the correlation of dyspnea scale with FL was stronger (rs > 0.5) than with FVC (rs < -0.3) or FEV1 (rs < -0.4) in both positions. In a multiple regression analysis FL remained the best predictor of dyspnea scale even after adjustment for FEV1 (% pred). Finally, FL was almost as sensitive as FEV1 (% pred) but much more specific in assessing the severity of dyspnea scale. These findings suggest that expiratory flow limitation as measured by the negative expiratory pressure technique may be more useful in the evaluation of dyspnea in patients with COPD than spirometry measurements.

Aged↗
PubMed1995

Passive smoking and evolution of lung function in young adults. An 8-year longitudinal study.

The objective of the study was to examine the relation between exposure to environmental tobacco smoke (ETS) and the rate of change in ventilatory lung function in young adults during a study period of 8 years, with an additional aim to recognize susceptible subgroups. The study population consisted of 117 never smokers, who were 15-40 years of age at the time of an initial examination when they underwent spirometry and a standardized interviewer-administered questionnaire on respiratory health, and were re-examined 8 years later. Lifetime exposure to ETS at home and at work before the start of the study was ascertained at an early stage of the study, and exposure during the study period was recorded at the 8-year examination. The relations between home and work ETS exposure before and during the study period and the rate of change in forced expiratory volume in one second (delta FEV1 in ml/yr) and in mean forced expiratory flow during the middle half of the forced vital capacity (delta FEF25-75 in 1/sec/yr) were studied in linear regression models including potential confounders and other determinants of the outcome. There was no statistically significant relation between ETS exposure during or before the study period and evolution of FEV1 or FEF25-75. The 95% confidence intervals of the estimates indicated that ETS exposure was unlikely to have a physiologically relevant effect. A statistically significant but physiologically unimportant relation was observed between cumulative home ETS exposure before the study and delta FEV1 in the subgroup of subjects 25 years of age or younger. There was no evidence of modification by atopy, wheezing or gender. The results suggest that exposure to environmental tobacco smoke in young adulthood at home and in office work environment does not lead to a clinically important ventilatory impairment in such exposure levels as experienced in Canadian housing conditions. This does not refute the possibility that higher exposure due to more frequent smoking in smaller indoor spaces with lower rates of ventilation may be harmful.

Adolescent↗
PubMed1995

International union against tuberculosis and lung disease (IUATLD): initiatives in non-tuberculous lung disease.

IUATLD initiatives in non-tuberculous lung disease developed in the late 1970s, coincident with improving tuberculosis control, and have targeted acute respiratory infections in children and chronic airways disease in adults and in children. The focus has been on methodology and the tools required to document the distribution and determinants of disease, and is illustrated in data gathered in African populations. Instruments developed include a simplified method of measuring bronchial hyper-reactivity and an asthma questionnaire Non-standard methods of questionnaire administration have also been validated, methods which are appropriate for use in the burgeoning urban communities and workforces of sub-Saharan Africa made up of rural migrants from different tribes and language groups. In addition, a review of reference values available for interpreting lung function in sub-Saharan African populations indicates a need to take into account a secular trend over the last two decades towards higher spirometric values. In the published data from Africa, not inconsiderable between-country differences are evident in the prevalence of chronic bronchitis in adults and of asthma in children. In addition, rates for childhood asthma were consistently higher in urban vs rural communities, with environmental factors playing an important role as well as being locally specific. Not only does the burden of morbidity attributable to both the chronic airway diseases reviewed justify past IUATLD initiatives in non-tuberculous lung disease, but it also argues that future initiatives should focus on investigating between- and within-country differences using a standardized methodology, with a view to identifying local environmental determinants susceptible to intervention and control. Curbing tobacco use is clearly important, not only to benefit the health of adult smokers for whom the ill-health consequences have long been recognized, but, and more important, to protect the health of children, born and unborn, with whom they share the environment.

Adolescent↗
PubMed1995

Socioeconomic status and indicators of asthma in children.

Differential access and utilization of medical care by the poor and rich may contribute to differences in asthma prevalence. We therefore studied the relationship of socioeconomic status (SES) to various indicators of asthma in the Canadian context of universal access to medical care. Information on respiratory symptoms, demographics, and home exposures of 1,111 primary school children was collected by questionnaire. Parental occupation was used to establish SES. Exercise-induced bronchospasm (EIB) after a 6-min free-running test was our measure of airways responsiveness and was available for 989 children. As compared with children from the most advantaged homes, children from the least advantaged homes were more likely to present EIB (OR: 2.26, 95% CI: 1.12 to 4.58) and to report night cough (OR: 2.30, 95% CI: 1.04 to 5.06) and cough with mucus (OR: 3.15, 95% CI: 1.06 to 9.33), while there was no significant excess of the report of wheeze or diagnosed asthma. Among factors potentially linked to SES, the presence of a cat at home (OR: 1.63, 95% CI: 1.02 to 2.61) and lower respiratory infection before 2 yr of age were associated with an excess of EIB (OR: 1.71, 95% CI: 1.16 to 2.52). Our results suggest that unidentified environmental factors contribute to the excess asthma morbidity in poor children.

Adolescent↗
PubMed1994

The relationship of urgent hospital admissions for respiratory illnesses to photochemical air pollution levels in Montreal.

The relationship between the number of daily urgent hospital admissions for respiratory illnesses (31 hospitals) and ambient air pollution in Montreal, Canada, was investigated for warm periods between 1984 and 1988. Air pollutants included 1-hr and 8-hr maximum ozone, estimated particulate matter < or = 10 microns in aerometric diameter (PM10), and estimated sulfate (SO4(2-) fraction of PM10. Regression analyses controlled for seasonal and day-of-week trends, autocorrelation, temperature, and relative humidity. For July and August periods, there was a statistically significant (P < 0.01) univariate relationship of all respiratory admissions to 8-hr maximum ozone, which became nonsignificant when coregressed with temperature. Levels of ozone which never exceeded the U.S. National Ambient Air Quality Standard (NAAQS) of 120 ppb and high intercorrelations between ozone, particulates, and temperature may explain this finding. Asthma admissions in the May-October periods increased by 2.7% over mean levels for each 12 micrograms/m3 increase in PM10 levels 3 days prior to the admission day (95% confidence interval, 0.7 to 4.8%). In the July and August periods, hospital admissions for respiratory illnesses excluding asthma were 9.6% higher (95% confidence interval, 0.5 to 18.7%) when estimated SO4(2-) had exceeded 8.1 micrograms/m3 4 days prior to the admission day compared to days when SO4(2-) was at or below this level. There were no significant (P < 0.05) associations of a reference group of nonrespiratory admissions to air pollution after controlling for weather. The above results were found despite levels of PM10 which never exceeded the NAAQS of 150 micrograms/m3. The associations found are relevant to public health, since hospital admissions are expected to be accompanied by considerably more frequent occurrences of less serious outcomes. The present findings suggest that particulate air pollution during photochemically active periods is related to respiratory morbidity in Montreal.

Air Pollutants↗
PubMed1994

Estimation of unmeasured particulate air pollution data for an epidemiological study of daily respiratory morbidity.

The standard approach to government-mandated aerometric monitoring of airborne particulates across North America is to sample every sixth day year round. However, such data are inadequate for epidemiological studies which aim to examine daily time series relationships of particulate air pollution to respiratory health responses. The aim of the present study was to estimate missing daily particulate matter < or = 2.5 and < or = 10 microns in aerometric diameter (PM2.5 and PM10) and sulfate (SO4(2-) to a degree sufficiently accurate and reliable to allow the use of these estimates, along with the measured data, in an investigation of the relationship of air pollution to respiratory hospital admissions in Montreal during the 1980s. Prediction equations were developed for May through October periods using available daily levels of predictor variables which included: relative humidity-corrected light extinction coefficient (bext) derived from airport visual range sightings, coefficient of haze (COH), SO2, NOx, CO, O3, wind speed, wind direction, barometric pressure (BP), temperature, relative humidity, and total precipitation. Three fourths of the available gravimetric particulate data were used to develop prediction models, while the remaining fourth was used to test the reliability of the model (holdout data). All final models explained over 70% of the variability in the particulate air pollutants and were reliable when tested against the holdout data. The strongest (P < 0.001) and most consistent predictors were bext, COH, and O3 measured on the same day as the particulate, and BP lagged 1 day in the past. Other selected variables were same day NOx, BP, and minimum temperature. Although the present approach to the estimation of missing particulate air pollution may increase the level of exposure misclassification, it does allow for the use of existing network databases in epidemiological studies of daily air pollution health effects even though particulate data is only measured on certain days.

Air Pollutants↗
PubMed1994

Symptoms and pulmonary functions as measures of morbidity.

A contemporary list of non-malignant respiratory conditions associated with exposure to environments contaminated by chrysotile asbestos dust includes pulmonary parenchymal and pleural fibrosis, small airway abnormality and conditions affecting the large airways such as chronic bronchitis and chronic airflow limitation. The first two are attributed to the specific biological effects of asbestos dust, the latter two to nonspecific effects of exposure to mineral dusts and/or other airborne pollutants in workplaces contaminated by asbestos dust. Prevalence rates for all the clinical markers of morbidity (radiographic change, lung function deficit and symptoms) have been shown to increase with increasing exposure to chrysotile but more steeply when exposure is in textile and other manufacturing plants than in mining and milling. The presence of amphiboles such as tremolite in the airborne dust may also result in steeper exposure-response relationships, while exposure in crocidolite mining results in very much steeper exposure-response relationships. Clinical asbestosis, though less frequent and less severe than previously, is still associated with increased moribidity, while localized pleural fibrosis in the form of plaques with minimal or no parenchymal fibrosis, currently the most frequently encountered non-malignant asbestos related condition encountered in clinical practice, may also be associated with morbidity, including lung function deficit. Determinants of progression of chrysotile-related parenchymal and pleural radiographic abnormality include duration and time since first exposure and, possibly, continued exposure after first appearance of radiographic changes. Progression of asbestos-related airway disease, documented as lung function loss over time, may, under the influence of continued exposure, be comparable to the progression observed under the influence of continued smoking.

Adult↗
PubMed1994

A respiratory survey in a black Johannesburg workforce.

BACKGROUND: The burden and determinants of airway disease in the population of southern Africa, which is currently undergoing rapid, often uncontrolled, urbanisation and industrialisation, are unknown. Previous surveys have focused on specific occupational groups and few have included women. This paper describes the respiratory status in a 30% probability sample of 206 men and 203 women drawn from an urban black Johannesburg workforce of almost 1500, all working for an educational institution. METHODS: Subjects answered a respiratory questionnaire and performed spirometric tests. Symptom rates and age and height standardised forced vital capacity (FVC), forced expiratory volume in one second (FEV1), FEV1/FVC%, and forced expiratory flow (FEF25-75) were analysed by gender in relation to smoking, past work exposures, past and recent respiratory conditions, and socioeconomic indicators. RESULTS: Symptom prevalence was high, bronchitic symptoms in men being related to smoking and previous occupational exposure, and in women to smoking despite the low intensity of their habit. Phlegm and wheezing were related to childhood respiratory illness in both men and women. FVC and FEV1, based on all subjects including smokers, were higher than previously reported for black residents of southern Africa. FVC was also positively related to education and job category. Higher values for ever smokers than for never smokers suggested health selection into the habit, while significant negative smoking effects were seen only on FEV1/FVC% and only in women. CONCLUSIONS: Despite the high prevalence of symptoms--some smoking related--in this urban workforce, lung function levels were higher than previously reported in African blacks, and may reflect improving socioeconomic conditions.

Adult↗
PubMed1994

Review and analysis of variation between spirometric values reported in 29 studies of healthy African adults.

Within- and between-population variation in spirometric measurements has been addressed in a systematic review of spirometric measurements from 29 studies published between 1965 and 1990 involving 9,690 men and 2,638 women of sub-Saharan African ancestry; FVC and FEV1 were age- and height-standardized at BTPS. Between- population differences were related to geographic region and sample source (workforce versus community). The effects of altitude, variation in sample mean height, and year of study publication were also significant variables in multivariate models explaining between-population differences. Altitude was the most important variable with an effect of 263 ml/1,000 m (95% confidence interval [CI] 120-410) on FVC in men. In women, variation in sample mean height was also important, with taller populations having larger values for FVC (64 ml/cm). In men, secular trends were evident, with date of study associated with negative trends among men in the U.S.A. (-35.3 ml/year), and positive trends (14.7 ml/year) in other regions. These differences in trend could not be explained. Population selection factors, altitude, date of study, and other biological sources of variation need to be taken into account in evaluating between- and within-population comparisons of spirometric measurements.

Adult↗
PubMed1994

Documentation of ill-health effects of occupational exposure to grain dust through sequential, coherent epidemiologic investigation.

This review describes the evolution in epidemiologic methods (study design, outcome, and exposure measurements and target population) in relation to knowledge gained concerning the ill-health effects of exposure to grain dust in the workplace over the past three decades. The clinical conditions associated with grain dust exposure are briefly described. Thereafter the study approaches used to investigate grain-related conditions (clinical studies, workforce-based prevalence studies, prevalence studies including unexposed workers, short-term response to exposure, longitudinal studies, supporting evidence from other research arenas, and studies documenting dose-response relationships) are discussed. The objective is to illustrate the strength of sequential, coherent epidemiologic investigation into the ill effects of a particular work environment on human health.

Agricultural Workers' Diseases↗
PubMed1993

An environmental and respiratory health survey of workers in a grain mill in the Johannesburg area, South Africa.

A respiratory health survey was conducted in a grain mill and the relationship of health indicators to quantitative measures of airborne dust, fungal, and bacterial contamination was examined. Respiratory symptoms were more prevalent in the high dust exposure categories; lung function levels were also higher in the high dust exposure categories, consistent with a "healthy" worker effect. Workers in the three higher dust exposure categories showed either no change or a decrease in lung function over the working week, while workers in the low exposure category demonstrated an improvement in lung function over the working week. Total dust and microbiological (fungal and bacterial) load were found to be significantly related to each other, and the relationship of microbiological load to lung function level and changes over the working week were similar to those found for total dust.

Adult↗
PubMed1993

Relationship of respiratory health status to grain dust in a Witwatersrand grain mill: comparison of workers' exposure assessments with industrial hygiene survey findings.

Objective measures of exposure furnished by dust monitoring are both costly and time consuming and require a sufficient level of technology. However, they are important in demonstrating exposure-response relationships, in furnishing information necessary to establish environmental control levels, and to assess if interventions, for instance, improving dust control, have been effective. In this paper respiratory symptoms and cross-shift changes in spirometric lung function were related to dust exposure level in a grain mill assessed in two ways, subjectively (by workers themselves on a four point scale) and objectively (by personal dust monitoring). Health indicators that depend on the individual's perception (e.g., symptoms) correlated more closely with the subjectively assessed dust category, while health indicators that were measured objectively (e.g., cross-week FVC and FEV1 change) correlated more closely with the objectively assessed dust category. However, the patterns of relationship of respiratory health indicators to either dust category were similar, and exposure assessed by one method was, to a large extent, a proxy for the other. The most significant predictor of workers' choice of dust exposure category was the measured dust level. These findings indicate that exposure categories based on workers' assessment of dustiness can be a useful tool in etiologic research, in particular in establishing exposure-response relationships.

Dust↗
PubMed1993

Respiratory symptoms in young adults should not be overlooked.

The purpose of this study was to examine the relation between development of respiratory symptoms and the rate of change in ventilatory lung function in young adults during a study period of 8 yr. The study population consisted of 391 subjects who were 15 to 40 yr of age at initial examination, when they underwent spirometry and an interviewer-administered ATS-DLD-78-A questionnaire on respiratory health, and who were reexamined 8 yr later. The association between the development of symptoms and the rate of change in FEV1 over time (delta FEV1, ml/yr) was studied in a linear regression model that included the potential confounders and other determinants of the outcome. The presence of modification by such factors as smoking, childhood exposure to environmental tobacco smoke, gender, or atopy was assessed by the significance of interaction terms between potential modifiers and incident symptoms. Subjects who developed wheezing and dyspnea and in whom a doctor diagnosed asthma had a significantly greater average annual change in FEV1 compared with those without respiratory symptoms or asthma (-12.3 ml/yr, SE 5.0; -16.2 ml/yr, SE 5.5; and -42.6 ml/yr, SE 11.5, respectively). When focusing on subjects without a diagnosis of asthma, the associations with appearance of wheezing and dyspnea remained significant. The associations were in general stronger in never smokers compared with smokers and were strongest in ex-smokers. The presence of atopy was a significant modifier, so that in subjects with atopy there was a stronger negative association between the onset of cough and asthma and delta FEV1 than in those without.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Questionnaire assessments of recent exposure to environmental tobacco smoke in relation to salivary cotinine.

The increasing evidence of the ill-health effects of environmental tobacco smoke (ETS) has prompted the search for accurate measures of exposure to ETS. The present study examined whether it was possible to enhance the ability of questionnaire-derived assessments of ETS exposure, to predict salivary cotinine. Salivary samples were obtained from 258 nonsmoking bank employees, who simultaneously answered questions detailing their exposure to second-hand smoke within the last three days. Exposure models were created, to take into account the number of smokers nearby, length of time in their presence, half-life of cotinine in bodily fluids, level of aversion to cigarette smoke and time of year. All models, including the consideration of intensity and duration of exposure combined, explained an equal amount of variance of log cotinine levels (approximately 16%). The weak relationship between questionnaire estimates of ETS exposure and cotinine, found in the present study, suggests that further investigation is needed to improve the assessment of recent ETS exposure.

Adult↗
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↗