Direct effects of leisure-time physical activity on walking speed.

OBJECTIVE: This study quantifies the effects of leisure-time physical activity (LTPA) on walking speed independently of body composition in an elderly cohort, and in those elderly with metabolic derangements due to age, diabetes, and cardiovascular disease (CVD). METHODS: 1655 community-dwelling women and men >55 years were measured for body composition (lean mass : fat mass ratio, LNFAT) , based on estimated bioelectric impedance by using population-specific prediction equations derived from dual-energy x-ray absorptiometry. In addition to LNFAT, LTPA, diabetes, CVD, walking speed, and other covariates were measured biannually over an 8-year period. LTPA was categorized as <22.5 Mets/week, ≥ 22.5 Mets/week, based on public-health recommended guidelines, and LNFAT was dichotomized based on its sex-specific median. Direct effects of high vs. low LTPA on walking speed were estimated for fixed levels of LNFAT, which represented an intermediary variable in the analysis. Stratified estimates of effects were obtained using subject status (e.g., age≥75 years, diabetes, CVD) at each visit. RESULTS: Walking speed was significantly greater (0.74, 0.75 m/s in women and men, respectively) if subjects experienced LTPA ≥22.5 Mets/week and > median LNFAT, compared with <22.5 Mets/week and ≤ median LNFAT (0.68, 0.69 m/s). While direct effects of LTPA contributed to higher walking speed, none were significant in the overall, nor the stratified groups of subjects, of either sex. CONCLUSIONS: Walking speed increases with greater LTPA and LNFAT in the elderly, but there was no evidence to indicate that walking speed increases from LTPA independently of body composition and the metabolic processes it represents.

Fungi and pollen exposure in the first months of life and risk of early childhood wheezing.

BACKGROUND: Many studies have found that the risk of childhood asthma varies by month of birth, but few have examined ambient aeroallergens as an explanatory factor. A study was undertaken to examine whether birth during seasons of elevated ambient fungal spore or pollen concentrations is associated with risk of early wheezing or blood levels of Th1 and Th2 type cells at 24 months of age. METHODS: 514 children were enrolled before birth and followed to 24 months of age. Early wheezing was determined from medical records, and Th1 and Th2 type cells were measured in peripheral blood using flow cytometry. Ambient aeroallergen concentrations were measured throughout the study period and discrete seasons of high spore and pollen concentrations were defined. RESULTS: A seasonal pattern was observed, with birth in autumn to winter (the spore season) associated with increased odds of early wheezing (adjusted odds ratio 3.1; 95% confidence interval 1.3 to 7.4). Increasing mean daily concentrations of basidiospores and ascospores in the first 3 months of life were associated with increased odds of wheeze, as were increasing mean daily concentrations of total and specific pollen types. Levels of Th1 cells at age 24 months were positively associated with mean spore concentrations and negatively associated with mean pollen concentrations in the first 3 months of life. CONCLUSIONS: Children with higher exposure to spores and pollen in the first 3 months of life are at increased risk of early wheezing. This association is independent of other seasonal factors including ambient levels of particulate matter of aerodynamic diameter

Effects of antioxidant enzyme polymorphisms on ozone-induced lung function changes.

Chronic exposure to ozone (O(3)) can cause changes in lung function that may reflect remodelling of small airways. It is likely that antioxidant enzyme function affects susceptibility to O(3). The aim of the present study was to determine whether polymorphisms in antioxidant enzyme (GSTM1, GSTP1 and NQO1) genes affect the risk of lung function changes related to chronic exposure to O(3). In total, 210 young adults who participated in a previous study, which showed a relationship between lifetime exposure to O(3) and decreased lung function, were genotyped. Multivariable linear regression was used to model sex-specific associations between genotypes and O(3)-related lung function changes, adjusting for height, weight, lifetime exposure to nitrogen dioxide and particles with a 50% cut-off aerodynamic diameter of 10 mum, and self-identified race/ethnicity. The GSTM1-null/NQO1 Pro187Pro-combination genotype was significantly associated with increased risk of an O(3)-related decrease in mean forced expiratory flow between 25-75% of forced vital capacity in females (parameter estimate+/-se -75+/-35 mL.s(-1)), while the GSTP1 Val105 variant genotypes were significantly associated with greater risk of an O(3)-related decrease in mean forced expiratory flow at 75% of forced vital capacity in males (-81+/-31 mL.s(-1)). GSTM1-null status was not significantly associated with any O(3)-related changes in lung function in either sex. The current authors conclude that the effects of antioxidant enzyme gene polymorphisms on the risk of decreased lung function related to chronic exposure to ozone may be modified by sex-specific factors.

Antioxidant intake, GSTM1 polymorphism and pulmonary function in healthy young adults.

Dietary antioxidants may protect lung tissue against reactive oxygen species-induced injury, adverse respiratory effects and reduced pulmonary function. Genetic variability in antioxidant enzymes also determines response to oxidative stress in the lung. The current authors evaluated whether lung function levels are associated with dietary intake of antioxidants and the glutathione S-transferase M1 (GSTM1) polymorphism. The current study cohort consisted of healthy, nonsmoking freshmen students who were lifetime residents in the Los Angeles or the San Francisco Bay areas (CA, USA). Participants completed comprehensive residential history, health history and food frequency questionnaires. Blood for genotyping was collected and forced expiratory volume measurements were obtained. Dietary vitamin C, magnesium and daily fruit servings were associated positively with forced expiratory volume in one second in males and with maximum mid-expiratory flow, forced expiratory flow after 75% of expelled volume, and the ratio of maximum mid-expiratory flow to forced vital capacity in females. In multivariable regression, vitamin C (or fruit for male students) and magnesium showed a consistent, positive association with lung function. Among healthy female adolescents, dietary intake of vitamin C is associated with increased levels of lung function. The current study does not support a role for the glutathione S-transferase M1-null genotype as an independent risk factor for decrements in lung function.

The effect of air pollution on inner-city children with asthma.

The effect of daily ambient air pollution was examined within a cohort of 846 asthmatic children residing in eight urban areas of the USA, using data from the National Cooperative Inner-City Asthma Study. Daily air pollution concentrations were extracted from the Aerometric Information Retrieval System database from the Environment Protection Agency in the USA. Mixed linear models and generalized estimating equation models were used to evaluate the effects of several air pollutants (ozone, sulphur dioxide (SO2), nitrogen dioxide (NO2) and particles with a 50% cut-off aerodynamic diameter of 10 microm (PM10) on peak expiratory flow rate (PEFR) and symptoms in 846 children with a history of asthma (ages 4-9 yrs). None of the pollutants were associated with evening PEFR or symptom reports. Only ozone was associated with declines in morning % PEFR (0.59% decline (95% confidence interval (CI) 0.13-1.05%) per interquartile range (IQR) increase in 5-day average ozone). In single pollutant models, each pollutant was associated with an increased incidence of morning symptoms: (odds ratio (OR)=1.16 (95% CI 1.02-1.30) per IQR increase in 4-day average ozone, OR=1.32 (95% CI 1.03-1.70) per IQR increase in 2-day average SO2, OR=1.48 (95% CI 1.02-2.16) per IQR increase in 6-day average NO2 and OR=1.26 (95% CI 1.0-1.59) per IQR increase in 2-day average PM10. This longitudinal analysis supports previous time-series findings that at levels below current USA air-quality standards, summer-air pollution is significantly related to symptoms and decreased pulmonary function among children with asthma.

Association of tobacco smoke exposure and respiratory syncitial virus infection with airways reactivity in early childhood.

Exposure to infectious agents and environmental tobacco smoke are thought to induce bronchial hyperresponsiveness (BHR). This study was undertaken to determine the effects of passive exposure to tobacco smoke and respiratory syncitial virus (RSV) lower respiratory infection (LRI) during infancy on the occurrence of BHR in the first 2 years of life. Eighty-six cases of documented RSV (mean age, 188 days) and 78 controls (mean age, 162 days) were enrolled from the clinic and in-patient service of a single hospital. None had a history of prior LRI. Subjects were studied at 6-month intervals up to 19 months of age with a standardized respiratory illness and parental smoking questionnaire, partial expiratory flow-volume curves by the "hug" (rapid thoracic compression) technique, and methacholine challenge. Exposure to maternal and paternal cigarette smoking, maternal history of asthma, and mold exposure were associated with decreased levels of length-corrected maximal flow at functional residual capacity (V'(maxFRC)). RSV-LRI was not related to V'(maxFRC). After adjustment of V'(maxFRC) for these factors, V'(maxFRC) was a significantly and positively correlated with a methacholine concentration provoking a 40% fall in V'(maxFRC) (PC40) and negatively correlated with dose-response slope. After adjustment for V'(maxFRC), there were no independent effects of tobacco smoke exposure or RSV-LRI on methacholine responses. These data do not support a role for RSV as a risk factor for airways reactivity in childhood and indicate that exposure to tobacco smoke affects airways reactivity through its effects on airways.

Correlates of cigarette smoking among Korean American adults in Alameda County, California.

OBJECTIVE: To estimate the prevalence of cigarette smoking and to determine the sociodemographic correlates of smoking among Korean American adults in Alameda County, California, 1994-1995. METHOD: Korean surname-based telephone survey; contingency table and multinomial logistic regression analyses. FINDINGS: Almost 39% of Korean American men and 6% of Korean American women were current smokers. Among Korean American men those who attended religious activities less than monthly had nearly three times the odds of being current smokers, and those who did not speak English well had 2 1/2 times the odds of being current smokers as compared to never smokers. Those 18 to 24 years of age had more than 8 1/2 times the odds, and those who attended religious activities less than monthly had more than 3 1/2 times the odds of being current smokers as compared to former smokers. Among Korean American women those who were not married had more than 3 times the odds of being current smokers, and those who attended religious activities less than monthly had 22 times the odds of being current smokers as compared to never smokers. Those who attended religious activities less than monthly had almost 8 times the odds of being current smokers as compared to former smokers. CONCLUSIONS: This study increases our understanding about the prevalence and correlates of cigarette smoking among Korean Americans and can contribute to the development of effective smoking cessation and prevention strategies in this understudied population.

Interim assessment of a community intervention to improve breast and cervical cancer screening among Korean American women.

Breast and cervical cancer screening practices are suboptimal among Korean American women. A community intervention program was launched in 1996 to improve breast and cervical cancer screening among Korean American women in Alameda County, California. After 18 months, interim program assessment revealed that mammograms improved, but Pap smears, breast self-examinations, and clinical breast examinations did not change significantly. However, results were similar for the control county probably because the program was not implemented fully. Several strategies for improving program implementation are discussed including recommendations for researchers planning community intervention projects.

The effect of ozone on inner-city children with asthma: identification of susceptible subgroups.

Within a cohort of 846 inner-city asthmatic children aged 4 to 9 yr, we looked for subgroups that were more susceptible to the effects of summer ozone. Daily diaries were compared with ambient ozone levels to evaluate effect modification by demographic and environmental characteristics. Children born > 3 wk prematurely or weighing < 5.5 lb. had greater declines in morning % peak expiratory flow rate (PEFR) (1.8% versus 0.3% per 15 ppb ozone, p < 0.05) and a higher incidence of morning symptoms (odds ratio = 1.42 versus 1.09 per 15 ppb ozone, p < 0.05) than did children who had been full-term infants of normal birthweight. Among children who had been of low birthweight (LBW) or had been premature infants, greater declines were seen among those whose reported baseline medication category was "no medication" (3.2% decline) or "steroids" (2.7%) as opposed to beta agonists or xanthines (0.8%) or cromolyn without steroids (0. 1%). Among the children who had been normal birthweight and full-term infants, the cromolyn without steroids group had the greatest declines in %PEFR (1.3%, versus < 0.5% in each of the other three groups). Nonatopic children also had greater responses to ozone. We conclude that among an asthmatic cohort, children who had had an LBW or a premature birth showed the greatest responses to ozone.

Long-term health effects of particulate and other ambient air pollution: research can progress faster if we want it to.

There is need for the assessment of long-term effects of outdoor air pollution. In fact, a considerable part of the large amount of U.S. research money that has been dedicated to investigate effects of ambient particulate pollution should be invested to address long-term effects. Studies that follow the health status of large numbers of subjects across long periods of time (i.e., cohort studies) should be considered the key research approach to address these questions. However, these studies are time consuming and expensive. We propose efficient strategies to address these questions in less time. Apart from long-term continuation of the few ongoing air pollution cohort studies in the United States, data from large cohorts that were established decades ago may be efficiently used to assess cardiorespiratory effects and to target research on detection of the most susceptible subgroups in the population, which may be related to genetic, molecular, behavioral, societal, and/or environmental factors. This approach will be efficient only if the available air pollution monitoring data will be used to spatially model long-term outdoor pollution concentrations across a given country for each year with available pollution data. Such concentration maps will allow researchers to impute outdoor air pollution levels at any residential location, independent of the location of monitors. Exposure imputation may be based on residential location(s) of participants in long-standing cardiorespiratory cohort studies, which can be matched to pollutant levels using geographic information systems. As shown in European impact assessment studies, such maps may be derived relatively quickly.

Current view of epidemiologic study designs for occupational and environmental lung diseases.

Epidemiologic studies long have played a role in the understanding of the effects of the general environment and various occupational exposures on the occurrence of acute and chronic diseases of the lung. This article is an overview of epidemiologic study designs that have particular relevance to studies of environmental and occupational lung disease. The application of times-series designs in the context of epidemiologic studies is discussed, as such designs have become widely used in studies of health effects ambient air pollution. The article emphasizes recent developments in the application of case-control study designs, many of which have had particular applications in epidemiologic studies related to environmental and occupational lung disease. These case-control designs offer efficient and valid alternatives for studies that in the past might have been conducted as more costly and time-consuming cohort studies.

Iron stores and coronary artery disease: a clinical application of a method to incorporate measurement error of the exposure in a logistic regression model.

Rates of coronary artery disease (CAD) increase sharply after menopause. We examined the hypotheses that high iron stores, as measured by plasma ferritin levels, are a risk factor for CAD and that the increase in iron stores after menopause is at least in part responsible for the rise in CAD in women. We also investigated measurement error of plasma ferritin using a Bayesian conditional independence model and incorporated it into the estimation of the odds ratio (OR) for males. Cases had >/=1 coronary artery stenosis >/=70%. Controls had no visible coronary lesions on angiography. The median plasma ferritin level was 48 mg/L (interquartile range: 28 to 86) among 244 cases and 45 mg/l (24 to 85) among 140 controls. The multivariate analyses among females, males, and females and males combined did not support an association between plasma ferritin levels and CAD (OR for one unit change in log ferritin 1.01, 95% CI 0.71-1.44, OR 0.95, 95% CI 0.66-1.37 and OR 0.95, 95% CI 0.75-1.21, respectively). Accounting for the measurement error of ferritin in males slightly improved the precision of the estimate of the OR but did not unmask an association (OR: 0.94, 95% CI 0.69-1.30). We conclude that high ferritin levels before or after menopause are not associated with CAD. Measurement error might be considered in situations where a one-time measurement is assumed to be representative of long-term exposure.

Oxygen uptake efficiency slope: an index of exercise performance and cardiopulmonary reserve requiring only submaximal exercise.

OBJECTIVES: We sought to evaluate, in adults, the efficacy of the Oxygen Uptake Efficiency Slope (OUES), an index of cardiopulmonary functional reserve that can be based upon a submaximal exercise effort. BACKGROUND: Maximal oxygen uptake (VO2,max), the most reliable measure of exercise capacity, is seldom attained in standard exercise testing. The OUES, which relates oxygen uptake to total ventilation during exercise, was proposed by Baba and coworkers (7) in a study of pediatric cardiac patients. They felt this submaximal index of cardiopulmonary reserve might be more practical than VO2max and more appropriate than the commonly used peak oxygen consumption (VO2 peak). METHODS: Treadmill exercise tests with simultaneous respiratory gas measurement were performed in 998 older subjects free of clinically recognized cardiovascular disease and 12 male patients with congestive heart failure. During incremental exercise, oxygen uptake was plotted against the logarithm of total ventilation, and the OUES was determined. RESULTS: The OUES, when calculated only from the first 75% of the exercise test, differed by 1.9% from the OUES calculated from 100% of exercise time in subjects with a peak respiratory exchange rate > or =1.10. On serial tests the OUES was less variable than exercise duration or VO2 peak. It correlated strongly with VO2max, with forced expiratory volume in 1 s and negatively with a history of current smoking. The OUES declined linearly with age in both women and men. A small sample of patients with congestive heart failure had OUES values much lower than those of older subjects without cardiovascular disease. CONCLUSIONS: The OUES is an objective, reproducible measure of cardiopulmonary reserve that does not require a maximal exercise effort. It integrates cardiovascular, musculoskeletal and respiratory function into a single index that is largely influenced by pulmonary dead space ventilation and exercise-induced lactic acidosis.

Reasons given by older people for limitation or avoidance of leisure time physical activity.

OBJECTIVES: This study investigates reasons given by older people for limitation or avoidance of physical exercise. DESIGN: Community-based longitudinal study of free-living persons age 55 years or older in Sonoma, California. METHODS: Baseline standardized interviews were conducted (n = 2046) as part of a longitudinal study of aging and physical performance. Seventeen reasons for limitation or avoidance of physical activities were evaluated, with responses grouped as: no limitations, medical, non-medical, and combined medical and non-medical reasons. Patterns of physical activity and medical conditions and direct measures of physical function were evaluated in relation to reasons for activity limitation by multinomial logistic regression. RESULTS: Women reported more limitations/avoidance of physical activity than men (81.0% vs 73.5%). Medical reasons increased with age. Reduced walking speed and depressive symptomatology were associated with a combination of medical and non-medical reasons in both sexes. Living arrangements were associated with non-medical reasons for women but were not for men. Non-medical reasons were associated with a 20 to 30% reduction in the number of subjects who reported physical activity at recommended levels. DISCUSSION: Non-medical factors are important determinants of activity limitation and should serve as targets for patient care providers and future interventions to improve participation in physical activity by older people.

Methods development for epidemiologic investigations of the health effects of prolonged ozone exposure. Part II. An approach to retrospective estimation of lifetime ozone exposure using a questionnaire and ambient monitoring data (California sites).

An extensive body of data supports a relation between acute exposures to ambient ozone and the occurrence of various acute respiratory symptoms and changes in measures of lung function. In contrast, relatively few data are available on the human health effects that result from long-term exposure to ambient ozone, Current efforts to study long-term ozone-related health effects are limited by the methods available for ascertaining lifetime exposures to ozone. The present feasibility study was undertaken as part of the Health Effects Institute's Environmental Epidemiology Planning Project (Health Effects Institute 1994) to (1) determine whether, in the context of an epidemiologic study, reliable estimates can be obtained for lifetime exposures to ozone by combining estimates from lifetime residential histories, typical activity patterns during life, and residence-specific ambient ozone monitoring data; (2) identify the minimum data required to produce reliable estimates of lifetime exposure; and (3) analyze the relations between various estimates of lifetime ozone exposure and measures of lung function. A convenience sample of 175 first-year students at the University of California, Berkeley, who lived all of their lives in selected areas of California (the Los Angeles Basin or the San Francisco Bay Area), were studied on two occasions (test and retest or test sessions 1 and 2), five to seven days apart. Residential and lifestyle data were obtained from a questionnaire: residence-based ambient ozone exposure values were assigned by interpolation of ambient ozone monitoring data to residential locations. Estimated lifetime exposure was based on average ozone levels between 10 a.m. and 6 p.m. and hours of exposure to ozone concentrations greater than 60 parts per billion (ppb). "Effective" lifetime exposure to ozone was based on a weighted average of estimated time spent in different ambient ozone environments as determined by different combinations of activity data. Pulmonary function was evaluated with flows and volumes from maximum expiratory flow-volume curves and slope of phase III of the single-breath nitrogen washout (SBNW) curves. Although the test-retest reliability of the residential history was acceptably high only for first and second residences, most of the unreliability for other residences came from residences occupied for relatively short durations. Therefore, the test-retest reliability of estimated lifetime exposure to ozone was high, with intraclass correlations greater than 0.90 for all approaches evaluated. Multiple, linear regression analyses showed a consistently negative relation between estimates of lifetime exposure to ozone and flows that reflect the physiology of pulmonary small airways. No relation was observed between lifetime ozone exposure and forced expiratory volume or the slope of phase III, and the relation between lifetime exposure and forced expiratory volume in one second was inconsistent. The results of the flow measures were unaffected by the method used to estimate lifetime exposure and gave effect estimates that were nearly identical. The data from this study indicate that useful and reproducible estimates of lifetime ozone exposure can be obtained in epidemiologic studies by using a residential history. However, the total burden of ozone to which the subjects were exposed cannot be determined accurately from such data. Nonetheless, the estimates so obtained appear to be associated with alterations in pulmonary function that are consistent with the predicted site of maximum effect of ozone in the human lung.

Exposure of young infants to environmental tobacco smoke: breast-feeding among smoking mothers.

OBJECTIVES: This study examined the degree to which breast-feeding and cigarette smoking by mothers and smoking by other household members contribute to the exposure of infants to the products of tobacco smoke. METHODS: The subjects were 330 mother-infant pairs derived from a cohort of 1000 pairs enrolled in a longitudinal study of the pulmonary effects of prenatal and postnatal smoking. The main outcome measure was corrected urinary cotinine levels. RESULTS: Urinary cotinine levels were 10-fold higher in breast-fed infants of smoking mothers than among bottle-fed infants of smoking mothers. Among infants of nonsmoking mothers, urine cotinine levels were significantly increased in infants living in homes with other smokers; in this group there was no significant difference between bottle-fed and breast-fed infants. Infants whose mothers smoked in the same room as the infant had only nonsignificant increases in cotinine levels compared with infants whose mothers restricted their smoking to other rooms. CONCLUSIONS: Breast-fed infants of smoking mothers have urine cotinine levels 10-fold higher than bottle-fed infants whose mothers smoke, suggesting that breast-feeding, rather than direct inhalation of environmental tobacco smoke, is the primary determinant of cotinine levels in infants whose mothers smoke.