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Jonathan M Samet

Publications and source records attributed to Jonathan M Samet.

At least 55 records · Page 3Linked to original sources
PubMed2004

Hospital admissions for heart disease: the effects of temperature and humidity.

BACKGROUND: We estimated the effects of temperature and humidity on hospital admissions for heart disease (International Classification of Diseases, 9th revision [ICD-9] codes 390-429) and myocardial infarction (ICD-9 code 410) of persons age 65 and older in 12 U.S. cities with a wide range of climates. To account for possible delayed effects and harvesting, we examined the impact of weather up to 20 days before each admission. METHODS: Poisson regression models were fitted in each city, with regression splines used to control for season and barometric pressure. We also controlled day of the week. We estimated the effect and the lag structure of both temperature and humidity based on a distributed lag model. FINDINGS: For cities in both hot and cold climates, we found that hospital admissions for all heart disease increased monotonically with average temperature on the same day as and the day before admission. The effect of very high temperatures had a temporal pattern consistent with harvesting: several days after an episode of high temperature, there were fewer admissions. In contrast, a protective effect of cold temperature persisted without rebound. The effects of either hot or cold temperature disappeared within 10 days of exposure. There was no evidence for a humidity effect. Similar but smaller effects of temperature were seen for admissions for myocardial infarction specifically. CONCLUSIONS: The effects of temperature on hospital admissions predominantly occur within a few days after exposure, and much of the effect of hot temperatures is short-term displacement of events.

Algorithms↗
PubMed2004

Time-series studies of particulate matter.

Studies of air pollution and human health have evolved from descriptive studies of the early phenomena of large increases in adverse health effects following extreme air pollution episodes to time-series analyses based on the use of sophisticated regression models. In fact, advanced statistical methods are necessary to address the challenges inherent in the detection of a relatively small pollution risk in the presence of potential confounders. This paper reviews the history, methods, and findings of the time-series studies estimating health risks associated with short-term exposure to particulate matter (PM), though much of the discussion is applicable to epidemiological studies of air pollution in general. We review the critical role of epidemiological studies in setting regulatory standards and the history of PM epidemiology and time-series analysis. We also summarize recent time-series results and conclude with a discussion of current and future directions of time-series analysis of particulates, including research on mortality displacement and the resolution of results from cohort and time-series studies.

Air Pollutants↗
PubMed2004

Environmental causes of lung cancer: what do we know in 2003?

The environmental causes of lung cancer have been the focus of intense epidemiologic and other research for > 50 years. The resulting evidence causally associates lung cancer with active and passive smoking, a variety of occupational agents, and indoor and outdoor air pollution. These causal associations have motivated control initiatives through education, regulation, and litigation. In recent years, the research focus has shifted to identifying the determinants of susceptibility to these agents, including interactions among environmental factors and genetic determinants of susceptibility to these agents. This article provides an overview of past and current research on the environment and lung cancer, and addresses the use of scientific evidence in controlling this cancer, which is largely caused by the environment.

Environment↗
PubMed2004

Risk assessment and child health.

Risk assessment, an approach for organizing information about hazards to health, safety, and the environment, provides a framework for gauging the threat to child health from environmental pollutants. A qualitative risk assessment has 4 components: hazard identification, dose-response assessment, exposure assessment, and risk characterization. In a risk assessment, consideration can be given to a population group that potentially has increased susceptibility, whether arising from having a high level of exposure or from increased susceptibility to the agent of concern on a biological basis. Children have been proposed as being at increased risk from some environmental agents, and there has long been concern and debate that the current approach of determining acceptable exposure levels or intake for a person may not yield safe intake limits for infants and children, who may be placed at greater risk than adults because of exposure patterns and inherent susceptibility. The persistence of debate on this critical public health issue reflects, in part, the difficulty of developing sufficiently sensitive and validated animal bioassays for critical outcomes. Epidemiologic studies can play only a limited role, given the complexity of establishing cohorts and tracking exposures from conception forward to assess risks across the lifespan. Meeting society's call for healthy environments for children poses an extraordinary challenge to researchers and to the policy makers who seek to develop evidence-based policies to protect children.

Child↗
PubMed2004

The National Morbidity, Mortality, and Air Pollution Study. Part III: PM10 concentration-response curves and thresholds for the 20 largest US cities.

Numerous studies have shown a positive association between daily mortality and particulate air pollution, even at concentrations below regulatory limits. These findings have motivated interest in the shape of the concentration-response relation. We developed flexible modeling strategies for time-series data that include spline and threshold concentration-response models. We applied these models to daily time-series data for the 20 largest US cities for 1987 through 1994, using concentration of particulate matter less than 10 microm in aerodynamic diameter (PM10*) as the exposure measure. The spline model showed a linear relation without indicating a threshold for the relative risks of death for all causes (total deaths) and for cardiovascular-respiratory causes in relation to PM10 concentration. By contrast, for causes other than cardiovascular-respiratory, the relative risk did not increase until the concentration reached approximately 50 microg/m3 PM10. For total mortality, a linear model without threshold was preferred to the threshold model and to the spline model, using the value of the Akaike information criterion (AIC). The findings were similar for combined cardiovascular and respiratory deaths. These findings indicate that linear models without a threshold are appropriate for assessing the effect of particulate air pollution on daily mortality even at current ambient levels.

Air Pollution↗
PubMed2003

Cancer risks attributable to low doses of ionizing radiation: assessing what we really know.

High doses of ionizing radiation clearly produce deleterious consequences in humans, including, but not exclusively, cancer induction. At very low radiation doses the situation is much less clear, but the risks of low-dose radiation are of societal importance in relation to issues as varied as screening tests for cancer, the future of nuclear power, occupational radiation exposure, frequent-flyer risks, manned space exploration, and radiological terrorism. We review the difficulties involved in quantifying the risks of low-dose radiation and address two specific questions. First, what is the lowest dose of x- or gamma-radiation for which good evidence exists of increased cancer risks in humans? The epidemiological data suggest that it is approximately 10-50 mSv for an acute exposure and approximately 50-100 mSv for a protracted exposure. Second, what is the most appropriate way to extrapolate such cancer risk estimates to still lower doses? Given that it is supported by experimentally grounded, quantifiable, biophysical arguments, a linear extrapolation of cancer risks from intermediate to very low doses currently appears to be the most appropriate methodology. This linearity assumption is not necessarily the most conservative approach, and it is likely that it will result in an underestimate of some radiation-induced cancer risks and an overestimate of others.

Biophysical Phenomena↗
PubMed2003

Airborne particulate matter and mortality: timescale effects in four US cities.

While time-series studies have consistently provided evidence for an effect of particulate air pollution on mortality, uncertainty remains as to the extent of the life-shortening implied by those associations. In this paper, the authors estimate the association between air pollution and mortality using different timescales of variation in the air pollution time series to gain further insight into this question. The authors' method is based on a Fourier decomposition of air pollution time series into a set of independent exposure variables, each representing a different timescale. The authors then use this set of variables as predictors in a Poisson regression model to estimate a separate relative rate of mortality for each exposure timescale. The method is applied to a database containing information on daily mortality, particulate air pollution, and weather in four US cities (Pittsburgh, Pennsylvania; Minneapolis, Minnesota; Seattle, Washington; and Chicago, Illinois) from the period 1987-1994. The authors found larger relative rates of mortality associated with particulate air pollution at longer timescale variations (14 days-2 months) than at shorter timescales (1-4 days). These analyses provide additional evidence that associations between particle indexes and mortality do not imply only an advance in the timing of death by a few days for frail individuals.

Air Pollution↗
PubMed2003

Variation in symptoms of sleep-disordered breathing with race and ethnicity: the Sleep Heart Health Study.

STUDY OBJECTIVES: To examine the relation of sleep-related symptoms to race and ethnicity in a diverse sample of middle-aged and older men and women. DESIGN: Cross-sectional questionnaire survey. SETTING: In the initial phase of the Sleep Heart Health Study, men and women enrolled in participating epidemiologic cohort studies were surveyed. PARTICIPANTS: 13,194 men and women 40 years of age and older, including 11,517 non-Hispanic white, 648 black, 643 American Indian, 296 Hispanic, and 90 Asian-Pacific Islander. INTERVENTIONS: Not applicable. MEASUREMENTS AND RESULTS: After adjustment for BMI and other factors, frequent snoring was more common among Hispanic women (odds ratio (OR) = 2.25, 95% confidence interval (CI) = 1.48, 3.42) and black women (OR = 1.55, 95% Ci = 1.13, 2.13) than among non-Hispanic white women. Hispanic men were significantly more likely to report frequent snoring than non-Hispanic white men (OR = 2.30, 95% CI = 1.43, 3.69). Black, American Indian, and Asian men did not differ significantly from white men in snoring prevalence. American Indian women were significantly more likely to report breathing pauses during sleep than their white, non-Hispanic counterparts (OR = 1.52, 95% CI 1.03, 2.24), although polysomnography data on a subset of the sample suggested that the association between this symptom reported on questionnaire and objective evidence of sleep-disordered breathing may be weaker among American Indians than among other groups. Mean Epworth Sleepiness Scale scores were slightly higher in black men and women than in their white, non-hispanic counterparts. CONCLUSIONS: Frequent snoring was more common among black and Hispanic women and Hispanic men than among their white non-Hispanic counterparts, even after adjusting for BMI and other factors. Further research including polysomnography and objective measurements of sleepiness is needed to assess the physiologic and clinical significance of these findings.

Adult↗
PubMed2003

Determinants of salivary cotinine concentrations in Chinese male smokers.

BACKGROUND: Identifying factors that affect cotinine levels in smokers may be useful for smoking cessation programs. Our aims were to characterize the distribution of salivary cotinine levels in Chinese smokers and to investigate factors that influence cotinine concentrations. METHODS: In a cross-sectional study, 600 Chinese adult smokers answered a questionnaire on smoking habits and provided a saliva sample for cotinine analysis. Modification of the relation between number of cigarettes smoked and cotinine concentration by individual characteristics, smoking behavior, and type of tobacco was evaluated. RESULTS: Quadratic model provided the best fit for the relation between number of cigarettes smoked in the previous 24 hours and salivary cotinine concentration. Among those smoking up to 20 cigarettes, the median cotinine concentration was higher among younger subjects, those smoking cigarettes without filter and regular rather than light cigarettes, and those inhaling frequently and deeply. Such trends were not observed among heavier smokers. The increase in cotinine per cigarette tended to be larger in those with lower median cotinine level. CONCLUSIONS: Our findings show that smoking behavior-related factors modify the relation between number of cigarettes smoked and salivary cotinine concentration. This suggests that smokers may regulate their smoking behavior to achieve a certain optimum nicotine level.

Adolescent↗
PubMed2003

ACE forum report: the making of an epidemiologist--necessary components for doctoral education and training.

The 2002 meeting of the American College of Epidemiology included an open forum on doctoral education and training in epidemiology. Discussion groups, facilitated by selected senior epidemiologists, recommended changes that would better prepare future epidemiologists to meet new challenges in public health and to build successful careers. The forum discussions were complemented by a panel of two doctoral students and two senior epidemiologists who provided their perspectives on each of the topics. Within discussion groups, agreement was clear on some issues and elusive on others. For example, good mentoring was considered a critical factor for a successful career, but how good mentoring can be promoted was a more complex issue. Likewise, experience with primary data collection should be a standard requirement for the doctoral degree, but the group's definition of primary data collection was more ambiguous. The recommendations derived from the education forum are summarized in this report, which may serve as an impetus for changes in the education and training of future epidemiologists.

Epidemiology↗
PubMed2003

National maps of the effects of particulate matter on mortality: exploring geographical variation.

In this paper, we present national maps of relative rates of mortality associated with short-term exposure to particulate matter < 10 micro m in aerodynamic diameter (PM(10)). We report results for 88 of the largest metropolitan areas in the United States from 1987 to 1994 for all-cause mortality, combined cardiovascular and respiratory deaths, and other causes of mortality. Maximum likelihood estimates of the relative rate of mortality associated with PM(10)and the degree of statistical uncertainty were obtained for each of the 88 cities by fitting a separate log-linear regression of the daily mortality rate on air pollution level and potential confounders. We obtained Bayesian estimates of the relative rates by fitting a hierarchical model that takes into account spatial correlation among the true city-specific relative rates. We found that daily variations of PM(10) are positively associated with daily variations of mortality. In particular, the relative rate estimates of cardiovascular and respiratory mortality associated with PM(10) are larger on average than the relative rate estimates of all-cause and other-cause mortality. The estimated increase in the relative rate of death from cardiovascular and respiratory mortality, all-cause mortality, and other-cause mortality were 0.31% (95% posterior interval, 0.15-0.5), 0.22% (95% posterior interval, 0.1-0.38), and 0.13% (95% posterior interval, -0.05 to 0.29), respectively. Bayesian estimates of the city-specific relative rates ranged from 0.23% to 0.35% for cardiovascular and respiratory mortality, from 0.18% to 0.27% for all causes, and from 0.10% to 0.20% for other causes of mortality. The spatial characterization of effects across cities offers the potential to identify factors that could influence the effect of PM(10) on health, including particle characteristics, offering insights into mechanisms by which PM(10) causes adverse health effects.

Air Pollutants↗
PubMed2003

Epidemiology of lung cancer.

In the United States, lung cancer remains the leading cause of cancer death in both men and women even though an extensive list of risk factors has been well-characterized. Far and away the most important cause of lung cancer is exposure to tobacco smoke through active or passive smoking. The reductions in smoking prevalence in men that occurred in the late 1960s through the 1980s will continue to drive the lung cancer mortality rates downward in men during the first portion of this century. This favorable trend will not persist unless further reductions in smoking prevalence are achieved.

Diet↗
PubMed2003

Indoor environments and health: moving into the 21st century.

The quality of our indoor environments affects well-being and productivity, and risks for diverse diseases are increased by indoor air pollutants, surface contamination with toxins and microbes, and contact among people at home, at work, in transportation, and in many other public and private places. We offer an overview of nearly a century of research directed at understanding indoor environments and health, consider current research needs, and set out policy matters that need to be addressed if we are to have the healthiest possible built environments. The policy context for built environments extends beyond health considerations to include energy use for air-conditioning, selection of materials for sustainability, and design for safety, security, and productivity.

Air Pollution, Indoor↗
PubMed2002

On the use of generalized additive models in time-series studies of air pollution and health.

The widely used generalized additive models (GAM) method is a flexible and effective technique for conducting nonlinear regression analysis in time-series studies of the health effects of air pollution. When the data to which the GAM are being applied have two characteristics--1) the estimated regression coefficients are small and 2) there exist confounding factors that are modeled using at least two nonparametric smooth functions--the default settings in the gam function of the S-Plus software package (version 3.4) do not assure convergence of its iterative estimation procedure and can provide biased estimates of regression coefficients and standard errors. This phenomenon has occurred in time-series analyses of contemporary data on air pollution and mortality. To evaluate the impact of default implementation of the gam software on published analyses, the authors reanalyzed data from the National Morbidity, Mortality, and Air Pollution Study (NMMAPS) using three different methods: 1) Poisson regression with parametric nonlinear adjustments for confounding factors; 2) GAM with default convergence parameters; and 3) GAM with more stringent convergence parameters than the default settings. The authors found that pooled NMMAPS estimates were very similar under the first and third methods but were biased upward under the second method.

Air Pollution↗