Geographical variations in the prevalence of atopic sensitization in six study sites across Canada

BACKGROUND

Geographical variations in atopic sensitization in Canada have not been described previously. This study used the standardized protocol of the European Community Respiratory Health Survey-1 (ECRHS-1) to investigate the distribution and predictors of atopic sensitization in six sites across Canada and to compare the results with some ECRHS-1 centers.

METHODS

Adults aged 20-44 years in six study sites across Canada underwent allergy skin testing using 14 allergens (Dermatophagoides pteronyssinus, Dermatophagoides farinae) cat, cockroach, grasses (Timothy grass, Kentucky grass), molds (Cladosporium herbarium, Alternaria alternata, Aspergillus fumigatus, Penicillium), trees (tree mix, birch, Olea europea), and common ragweed.

RESULTS

The overall prevalence of atopy (skin test over 0 mm to any allergen) was 62.7%. There was significant geographical variation in the prevalence of atopy in the six study sites (lowest 55.6% [95% C.I.51.3-59.9] in Prince Edward Island, highest 66.0 [61.7-70.3] in Montreal) and of sensitization to each of the allergens tested even after adjustment for confounders. When the first eight of the nine allergens in the ECRHS were used to estimate the prevalence of atopic sensitization, the prevalence of atopy in Canada was 57% compared with 35.2% overall for centers in the ECRHS. The prevalence of atopy in Vancouver (57% [52.3-61.8]) was close to that of Portland, Oregon (52.1% [46.2-58.0]).

CONCLUSION

There was a significant variation in atopic sensitization among different study sites across Canada. The prevalence of atopic sensitization is relatively high in Canada compared with sites in the ECRHS and this may, in part, account for the high prevalence of asthma and asthma symptoms in Canada.

Asbestos-related diseases of the lungs and pleura: uses, trends and management over the last century

Asbestos is a descriptive term for a group of naturally occurring minerals known to mankind since ancient times. The main types of asbestos (chrysotile, and the amphiboles crocidolite and amosite) differ in chemical structure, biopersistence in human tissue and toxicity. Commercial exploitation, with little thought for environmental controls, increased over the twentieth century, particularly after World War II, to accommodate globalisation and the demands of the world's burgeoning cities. As its ill-health effects, both non-malignant (fibrosis of the lungs or asbestosis; pleural effusion, plaques and thickening) and malignant (mesothelioma, lung and other cancers), became evident, public pressure rose to control its use. The last decades of the last century saw decreases in exposure and rates of asbestosis in industrialised and in some less-industrialised countries, where pleural plaques and malignant mesothelioma are currently the most frequent manifestations of asbestos exposure. Longer follow-up of asbestos-exposed cohorts in mining and manufacturing has also strengthened the evidence of a fibre gradient in toxicity, with chrysotile exhibiting lower toxicity than the amphiboles, and amosite lower toxicity than crocidolite. The last decades of the twentieth century saw stabilisation and/or declines in mesothelioma rates in several industrialised countries. In less-industrialised countries, data on disease are sparse, exposure generally high and rates may peak in the future. Management of asbestos-related disease in the workplace requires collaboration between workers and unions (responsible for monitoring workplace dust levels, to which they must have access) and companies (responsible for engineering controls), reinforced by appropriate government regulations and by community support.

Non-malignant consequences of decreasing asbestos exposure in the Brazil chrysotile mines and mills

AIMS

To investigate the consequences of improvement in the workplace environment over six decades (1940-96) in asbestos miners and millers from a developing country (Brazil).

METHODS

A total of 3634 Brazilian workers with at least one year of exposure completed a respiratory symptoms questionnaire, chest radiography, and a spirometric evaluation. The study population was separated into three groups whose working conditions improved over time: group I (1940-66, n = 180), group II (1967-76, n = 1317), and group III (1977-96, n = 2137).

RESULTS

Respiratory symptoms were significantly related to spirometric abnormalities, smoking, and latency time. Breathlessness, in particular, was also associated with age, pleural abnormality and increased cumulative exposure to asbestos fibres. The odds ratios (OR) for parenchymal and/or non-malignant pleural disease were significantly lower in groups II and III compared to group I subjects (0.29 (0.12-0.69) and 0.19 (0.08-0.45), respectively), independent of age and smoking status. Similar results were found when groups were compared at equivalent latency times (groups I v II: 30-45 years; groups II v III: 20-25 years). Ageing, dyspnoea, past and current smoking, and radiographic abnormalities were associated with ventilatory impairment. Lower spirometric values were found in groups I and II compared to group III: lung function values were also lower in higher quartiles of latency and of cumulative exposure in these subjects.

CONCLUSIONS

Progressive improvement in occupational hygiene in a developing country is likely to reduce the risk of non-malignant consequences of dust inhalation in asbestos miners and millers.

Risk factors for bronchial hyperresponsiveness in late childhood and early adolescence

The prevalence of asthma and bronchial hyperresponsiveness (BHR) tends to decrease in male children but increase in female children in the transition from childhood to adolescence. Hormonal factors may be involved in the natural history of asthma during this period. In a prospective study of Montreal school children, the authors examined the determinants of BHR according to the child's pubertal status; 156 male children and 168 female children without a prior diagnosis of asthma were followed for an average of 4.6 yrs. Average age at follow-up was 13.4 yrs and 59% had reached puberty. The prevalence of BHR at follow-up was similar among pre- and postpubertal male children (25.0% versus 29.2%),while BHR was more common among post- compared with prepubertal female children (33.1% versus 14.2%). There were no differences in the determinants (measured in childhood) of BHR at follow-up according to pubertal status. The major determinant of BHR was a positive skin test to dust-mite antigen. BHR was also linked to exposure to gas cooking and the presence of exercise-induced bronchospasm. In conclusion, the results of this study do not support a change in asthma phenotype with the onset of puberty. Pre- and postpuberty, the major determinant of bronchial hyperresponsiveness was skin sensitivity to mite allergen.

Association between vitamin A status and lung function level in children aged 6--9 years in Wukro wereda, Northern Ethiopia

BACKGROUND

In developing countries, studies using morbidity recalls to evaluate the benefits of vitamin A on respiratory health in children under 6 years of age have been inconclusive. This relationship has not been examined in older children. Spirometric measurements, an objective means of assessing respiratory health, require the subject's collaboration and have been successfully used in children over 6 years of age. This report describes a cross-sectional analysis of the relationship between lung function and vitamin A status in an area endemic to vitamin A deficiency.

METHODS

The data on which this report is based were gathered prior to the implementation of a prospective trial of the effect of vitamin A supplementation on lung function level in Northern Ethiopia. Vitamin A status was assessed by the Modified Relative Dose Response (MRDR) method and lung function assessed by spirometry in 702 rural children aged 6--9 years. Demographic, personal health, household, environmental and socioeconomic data were gathered by questionnaire.

RESULTS

In children with low vitamin A reserve, the unadjusted forced expiratory volume in one second (FEV(1)) was 48.8 ml (P = 0.006) lower than in those with adequate reserve. This difference was 23.1 ml (P = 0.04) when adjusted for age, gender and height and 14.1 ml (P = 0.20) when adjusted for children's demographic, general health, lung function and household-related characteristics.

CONCLUSION

Although these findings suggest that vitamin A plays a relatively minor role in determining FEV(1) level, interpretation is limited by the cross-sectional design. Further clarification of its role requires a trial of vitamin A supplementation.

Prevalence of asthma symptoms among adults aged 20-44 years in Canada

BACKGROUND

Reported prevalence rates of asthma vary within and between countries around the world. These differences suggest environmental factors in addition to genetic factors in the cause of the disease and may provide clues for preventive strategies. We examined the variability of asthma-related symptoms and medication use among adults in 6 sites across Canada (Vancouver, Winnipeg, Hamilton, Montreal, Halifax and Prince Edward Island) and compared our findings with those from sites that had participated in a recent European survey.

METHODS

We used the same sampling strategy and standardized questionnaire as those used in the European Community Respiratory Health Survey (ECRHS). The 6 Canadian sites were selected to represent different environments with respect to climate, air pollution and occupational exposure. Community-based samples of 3000 to 4000 people aged 20-44 years were randomly selected in each site. Subjects were asked to complete the questionnaire by mail between March 1993 and November 1994. Prevalence rates (and 95% confidence intervals [CIs]) of asthma symptoms, self-reported asthma attacks and use of asthma medication were compared across the Canadian sites and with sites that had participated in the ECRHS.

RESULTS

The overall response rate of those selected to receive the questionnaire was 86.5% (range 74.5%-92.8%). The prevalence rates of most asthma symptoms varied significantly among the Canadian sites. For instance, 21.9% (Montreal) to 30.4% (Halifax) of the men and 24.0% (Vancouver) to 35.2% (Halifax) of the women reported wheezing in the year before the survey. Depending on the site, 4.4% to 6.3% of the men and 5.2% to 9.5% of the women reported an asthma attack in the last year, and 4.0% to 6.1% of the men and 4.9% to 9.7% of the women were currently using asthma medication. Prevalence rates of symptoms, asthma attacks and medication use did not change with age, but they were higher among women than among men. Compared with the results from the ECRHS sites, those from the Canadian sites were among the highest.

INTERPRETATION

Significant variation in the prevalence of asthma symptoms, asthma attacks and use of asthma medication between Canadian sites and international sites suggests environmental influences. Different combinations of factors in different sites may be responsible for the high prevalence rates and should be the subject of further research to guide clinical management and public health intervention.

Prevalence of vitamin A deficiency in children aged 6-9 years in Wukro, northern Ethiopia

OBJECTIVE

To determine the prevalence of vitamin A deficiency in children aged 6-9 years in northern Ethiopia.

METHODS

A cross-sectional study was carried out and the data were analysed for 824 (61.5%) of 1339 eligible children for whom there was complete information on biochemical vitamin A status, dietary vitamin A intake, ocular examination for xerophthalmia, and anthropometry.

FINDINGS

The prevalence of xerophthalmia was 5.8%; serum retinol levels were below 0.35 mumol/l and between 0.35 and 0.70 mumol/l in 8.4% and 51.1% of the children respectively. The liver vitamin A reserve (modified relative dose response ratio > or = 0.06) was low in 41.0% of the children.

CONCLUSION

The high prevalence of severe vitamin A deficiency in children aged 6-9 years indicates the need to reevaluate the practice of targeting vitamin A supplementation programmes on children under 6 years of age in areas where vitamin A deficiency is endemic.

Occupational asthma in adults in six Canadian communities

We examined the prevalence, population attributable risk (PAR), and clinical characteristics of occupational asthma (OA) in a randomly selected population in six communities in Canada. Our study followed the European Community Respiratory Health Survey protocol. A randomly selected population of 18,701 (87% response rate) persons from the study communities, ranging in age from 20 to 44 yr, completed an initial questionnaire, of whom 2,974 (39% response rate) attended the laboratory and completed supplementary questionnaires. Of these latter individuals, 383 had asthma. Asthma was defined as physician-diagnosed asthma, and adult-onset asthma was defined as a first attack at age 15 yr or older. We used several methods for estimating OA as follows: (1) reporting of a high-risk job (occupation and industry) for OA at the time of asthma onset (Probable OA); (2) reporting of exposure to a substance that may cause OA (Possible OA) while not in a high-risk job at the time of asthma onset; and (3) combination of the PAR for high-risk jobs and exposures. The prevalence (95% confidence interval [CI]) of Probable OA and Possible OA combined was 36.1% (31.3 to 41.0%) among subjects with adult-onset asthma. The occupations most commonly reported in association with OA were nursing in the Probable OA group and clerical and food preparation in the Possible OA group. The clinical characteristics and exposures reported by both groups were similar. The PAR for adult-onset asthma in high-risk jobs and exposures was 18.2%. The assessment of occupation and industry alone, rather than of exposures, may underestimate the contribution of occupational exposures to asthma prevalence.

Prevalence of exercise induced bronchospasm in Kenyan school children: an urban-rural comparison

BACKGROUND

Higher rates of exercise induced bronchospasm (EIB) have been reported for urban than for rural African schoolchildren. The change from a traditional to a westernized lifestyle has been implicated. This study was undertaken to examine the impact of various features of urban living on the prevalence of EIB in Kenyan school children.

METHODS

A total of 1226 children aged 8-17 years attending grade 4 at five randomly selected schools in Nairobi (urban) and five in Muranga district (rural) underwent an exercise challenge test. A respiratory health and home environment questionnaire was also administered to parents/guardians. This report is limited to 1071 children aged < or = 12 years. Prevalence rates of EIB for the two areas were compared and the differences analysed to model the respective contributions of personal characteristics, host and environmental factors implicated in childhood asthma.

RESULTS

A fall in forced expiratory volume in one second (FEV1) after exercise of > or = 10% occurred in 22.9% of urban children and 13.2% of rural children (OR 1.96, 95% CI 1.41 to 2.71). The OR decreased to 1.65 (95% CI 1.10 to 2.47) after accounting for age, sex, and host factors (a family history of asthma and breast feeding for less than six months), and to 1.21 (95% CI 0.69 to 2.11) after further adjustment for environmental factors (parental education, use of biomass fuel and kerosene for cooking, and exposure to motor vehicle fumes).

CONCLUSIONS

The EIB rates in this study are higher than any other reported for African children, even using more rigorous criteria for EIB. The study findings support a view which is gaining increasing credence that the increase in prevalence of childhood asthma associated with urbanisation is the consequence of various harmful environmental exposures acting on increasingly susceptible populations.

Urban-rural differences in questionnaire-derived markers of asthma in Kenyan school children

Grade 4 Kenyan children attending 10 randomly selected public primary schools in Nairobi (urban) and the Muranga District (rural) were surveyed to establish the prevalence of symptom markers of asthma and to assess the impact of urbanization. A respiratory health and home environment questionnaire was administered at school to parents or guardians. The questionnaire response rates were 94.2% (568/ 603) for Nairobi and 89.6% (604/674) for Muranga. The prevalence rates for asthma, defined as "attacks of shortness of breath with wheeze", were 9.5% for urban and 3.0% for rural children (odds ratio (OR) urban versus rural: 3.42; 95% confidence interval (CI): -1.96-5.91). This urban-rural gradient persisted after adjusting for urban-rural differences in host factors (including duration of breastfeeding and family history of asthma and/or allergy), but was largely explained by urban-rural differences in environmental factors, including indoor animals, sharing a bedroom with a smoker, parental education, house ventilation and exposure to motor vehicle fumes en route to school (adjusted OR: 1.59; 95% CI: 0.70-3.55). Similar results were obtained for all other symptoms. These findings confirm the clinical impression that asthma is an important illness in Kenya and underline the need for the further study of environmental factors amenable to intervention, particularly in urban areas.

The role of domestic factors and day-care attendance on lung function of primary school children

The results of studies examining the relationship of domestic factors to lung function are contradictory. We therefore examined the independent effects of maternal smoking during pregnancy, exposure to environmental tobacco smoke (ETS), the presence of a cat, type of heating and cooking used in the home and day-care attendance on lung function after controlling for socioeconomic status (SES). Nine hundred and eighty-nine children from 18 Montreal schools were studied between April 1990 and November 1992. Information on the child's health and exposure to domestic factors was collected by questionnaire. Spirometry was performed at school. The data were analysed by multiple linear regression with percent predicted FEV1, FVC, and FEV1/FVC as dependent variables. In the overall sample (both sexes combined), cat in the home (regression coefficient, beta = -1.15, 95% confidence interval, CI: -2.26-(-)0.05) and electric baseboard units (beta = -1.26, 95% CI: -2.39-(-)0.13) were independently associated with a lower FEV1/FVC, while day-care attendance (beta = -2.05, 95% CI: -3.71-(-)0.40) significantly reduced FEV1. Household ETS was significantly associated with increasing level of FVC (beta = 2.86, 95% CI: +0.55 to +5.17). In boys but not girls, household ETS (beta = -2.13, 95% CI: -4.07-(-)0.19) and the presence of a cat (beta = -2.19, 95% CI: -3.94-(-)0.45) were associated with lower FEV1/FVC. By contrast, day-care attendance was associated with lower FEV1 (beta = -2.92, 95% CI: -5.27-(-)0.56) and FEV1/FVC (beta = -1.53, 95% CI: -2.73-(-)0.33) in girls only. In conclusion, the results provide evidence that domestic factors and day-care attendance primarily affected airway caliber and gender differences were apparent in the effects of these factors.

Emergency room visits for respiratory illnesses among the elderly in Montreal: association with low level ozone exposure

Population-based studies of hospital usage have been used to identify the ongoing adverse impacts of photochemical air pollutants on respiratory health. In this study we examined the relationship between the number of daily emergency room (ER) visits for respiratory illnesses (25 hospitals) and outdoor air pollution in Montreal, Quebec (June-August, 1989-1990). Air pollutants measured included 1- and 8-h maximum ozone (O3) and estimated particulate matter < 2.5 microns in aerometric diameter (PM2.5). Seasonal and day-of-week trends, autocorrelation, temperature, and relative humidity were controlled for in-time series regressions. Although O3 levels never exceeded the U.S. National Ambient Air Quality Standard (NAAQS) of 120 ppb (maximum day, 106 ppb), statistically significant (P < 0.01) relationships were found between respiratory ER visits for patients over the age of 64 and both 1- and 8-h maximum O3 measured 1 day prior to the ER visit day during the 1989 summer: ER visits were 18.7% higher than average (95% Cl, 6.5-30.9%) for a mean increase of 44 ppb O3 (1-h maximum), and 21.8% higher than average (95% Cl, 9.7-33.8%) for a mean increase of 38 ppb O3 (8-h maximum). There was an association between respiratory ER visits for the elderly and estimated PM2.5 lagged 1 day (0.1 visit/microgram/m3 PM2.5, P < 0.07), but this was confounded by both temperature and O3. The only finding for a reference group of nonrespiratory conditions was an inverse association between ER visits for infants and O3, but this was confounded by weather. These findings confirm the impression that while air quality standards may protect the respiratory health of the general population, this is not the case for susceptible subgroups such as the elderly.

Exercise-induced bronchospasm: a pilot survey in Nairobi school children

Exercise-induced bronchospasm (EIB), a common feature of asthma in children, has been used as the outcome measure in community-based surveys of childhood asthma to circumvent difficulties arising from relative lack of objectivity in the use of questionnaires in communities with different cultural and language orientations. We report here the results of the first community-based study of childhood asthma in Kenya using EIB as the outcome measurement. The data was collected in a pilot study to develop methodology for a larger subsequent study. The survey targeted grade four children in five Nairobi City Council school each representing a neighbourhood social economic status (SES). Out of 597 eligible, 408 children took part in the study (68% participation rate). EIB defined as decline in FEV1 of 15% or more, post-exercise was found in 10.5% (95% CI; 10.3, 10.7) of the children studied, the highest rate reported so far in Africa. While boys were more likely to exhibit EIB compared to girls, the prevalence of EIB tended to decrease with age, especially among children residing in low SES neighbourhoods where the EIB prevalence rates tended to be lower compared to those among children from higher SES neighbourhoods. However, none of these differences was statistically significant. This study confirms the feasibility of undertaking exercise challenge tests in the African context and we recommend that additional studies of similar nature be carried out in other populations of Africa to explore the potential of using an exercise test as a marker of asthma in epidemiologic studies.

Effects of air pollution on emergency room visits for respiratory illnesses in Montreal, Quebec

As an approach to evaluating the public health burden from current air pollution levels, we examined the relationship of daily emergency room (ER) visits for respiratory illnesses (25 hospitals, average 98 visits/d) to air pollution in Montreal, Canada, from June through September, 1992 and 1993. Air pollutants measured included ozone (O3), particulate matter diameter < 10 microm (PM10) and < 2.5 microm (PM2.5), the sulfate fraction of PM2.5 (SO4), and aerosol strong acidity (H+). Temporal trends, autocorrelation, and weather were controlled for in time-series regressions. For 1992, no significant associations with ER visits were found. However, 33% of the particulate data were missing. For 1993, 1-h maximum O3, PM10, PM2.5, and SO4 were all positively associated with respiratory visits for patients over 64 yr of age (p < 0.02). An increase to the mean level of 1-h maximum O3 (36 ppb) was associated with a 21% increase over the mean number of daily ER visits (95% confidence interval [CI]: 8 to 34%). Effects of particulates were smaller, with mean increases of 16% (4 to 28%), 12% (2 to 21%) and 6% (1 to 12%) for PM10, PM2.5, and SO4, respectively. Relative mass effects were PM2.5 > PM10 >> SO4. Ozone and PM10 levels never exceeded 67 ppb and 51 microg/m3, respectively (well below the U.S. National Ambient Air Quality Standards of 120 ppb and 150 microg/m3, respectively). The present findings have public health implications with regard to the adverse health effects of urban photochemical air pollution on older individuals.

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.

Effect of passive smoking on the development of respiratory symptoms in young adults: an 8-year longitudinal study

The evidence of an association between passive smoking and occurrence of respiratory symptoms is relatively strong in children, whereas studies conducted in adult populations have provided inconsistent results. The objective of the present study was to examine the relations between exposure to environmental tobacco smoke (ETS) and development of respiratory symptoms in young adults during a study period of 8 years, with emphasis on the evaluation of potential dose-response pattern of the relations. The study population consisted of 117 "never smokers," who were 15 to 40 years of age at the time of initial examination, when they answered a standardized questionnaire on respiratory health, and who were reexamined 8 years later. ETS exposure at home and at work during the study period was recorded at the 8-year examination with a structured questionnaire. The symptoms studied as outcomes included wheezing, dyspnea, cough, and phlegm production. The relations between ETS exposure and development of respiratory symptoms were studied in multivariate logistic regression models controlling for age, gender, atopy, and the presence of other respiratory symptoms. Cumulative incidences of the respiratory symptoms, except of phlegm production, were consistently greater among subjects exposed to ETS compared with the reference group. A significant dose-related increase in the risk of developing dyspnea was observed in relation to ETS exposure, with an OR of 2.37 for an average exposure of 10 cigarettes/day (95% confidence interval, 1.25-4.51). The risk of developing other respiratory symptoms, apart from phlegm, was also related to ETS exposure, but these relations did not achieve statistical significance. The results provide evidence of adverse respiratory effects of ETS exposure in the home and office work environments in young adults. These findings emphasize the need for effective measures in the prevention of involuntary smoking during young adulthood.

Socioeconomic status and lung function among primary school children in Canada

We examined the relationship of lung function level to socioeconomic status (SES) using a cross-sectional design among 989 primary school children selected from 18 Montreal schools and studied between April 1990 and November 1992. Information on each child's health, demographics, home exposure to tobacco smoke, pets, and cooking and heating fuel used in the child's home was collected by questionnaire. Spirometry was performed at school. Parental occupation was used to establish SES. After adjusting for personal, familial, and environmental factors, in boys but not in girls, FEV1 and FVC were progressively larger in higher categories of SES (p < 0.001 for linear trend). After taking into account the effect of multiple comparisons and adjusting for personal, familial, and environmental factors, boys from families in the lowest category of SES were found to have an FEV1 lower by 8.2% (95% CI, -13.8 to -2.1) and an FVC lower by 8.1% (95% CI, -13.4 to -2.6) when compared with the most advantaged. These results provide evidence that socioeconomic status, independent of common indoor exposures, is a risk factor for lower FEV1 and FVC among boys.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Reliability of hospital data for population-based studies of air pollution

The use of hospital databases for research into the respiratory effects of air pollution has been questioned. In an attempt to address that issue, reabstracts of 1,279 discharge records from 14 Montreal hospitals were compared with the universal health insurance database of Quebec. Agreement levels on discharge diagnoses were 94.9% for asthma; 75.5% for all other respiratory diagnoses combined, including upper airway infections, pneumonia, and coronary obstructive pulmonary disease (COPD) (90% after ignoring disagreements between closely related respiratory diagnoses); and 93.1% for a nonrespiratory comparison group. Factors associated with misclassification included use of nonurgent admissions; delays in hospital admission from emergency rooms; and differences in levels of diagnostic agreement between hospitals, age groups, and outcome groups. These should be taken into account in air pollution epidemiologic research in which databases of the kind commonly maintained in North American health care systems are used.

Sources of variation in spirometric measurements. Identifying the signal and dealing with noise

Variation in spirometric lung function measurements can be ascribed to technical and biological sources and is conveniently classified as within- or between-subject and within- or between-population. A necessary first step is to identify which sources of variation constitute "noise" and which "signal" in the various applications in occupational medicine. This chapter proposes strategies to enhance signal and deal with noise, and it delineates areas in which additional research to strengthen existing information would maximize the usefulness of spirometric measurements.

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)

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)

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.

[Chronic occupational bronchitis and programs of medical surveillance]

Industrial bronchitis is of clinical significance when accompanied by irreversible obstruction of the airways. The controversy surrounding the role of dusty exposures in the workplace in the genesis of chronic obstructive lung disease derives from the numerous biases inherent in prevalence studies of working populations often used to study this relationship. Better study designs afforded by community based and longitudinal studies have clearly demonstrated the causal role of dusty exposures in chronic airflow obstruction. This abnormality is detected by spirometry, a technique commonly applied in surveillance programs of industrial workers. The large differences seen in these measures even among normal subjects as well as their variability from time to time do not allow the identification of affected individuals before the onset of significant irreversible disease. For this reason these tests are useful mainly for case detection while prevention must rely on better industrial hygiene.

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.

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.

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.

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.