Recovering true risks when multilevel exposure and covariables are both misclassified.

The authors extend previous results on nondifferential exposure misclassification to the situation in which multilevel exposure and covariables are both misclassified. They show that if misclassification is nondifferential and the predictive value matrices are independent of other predictor variables it is possible to recover the true relative risks as a function of the biased estimates and the misclassification matrices alone. If the covariable is a confounder, the true relative risks may be recovered from the apparent relative risks derived from misclassified data and the misclassification matrix for the exposure variable with respect to its surrogate.

Linear extrapolation models of lung cancer risk associated with exposure to environmental tobacco smoke.

This paper presents a model to estimate the number of lung cancer deaths due to ETS exposure among the 1992 U.S. never-smoking population, based on downward linear extrapolation from the estimated risks of active smokers.

Use of multiple surveys to estimate mortality among never, current, and former smokers: changes over a 20-year interval.

Objectives: This study sought to demonstrate how data from publicly available large-scale cross-sectional health surveys can be combined to analyze changes in mortality risks among never, current, and former smokers.

Methods: Data from the 1966/68 and 1986 National Mortality Followback Surveys and the 1970 and 1987 National Health Interview Surveys were used to estimate the distribution of never, current, and former smokers among the US population at risk and decedents. Standardized mortality ratios and quotients of standardized mortality ratios were used to estimate mortality risks.

An alternative explanation for the apparent elevated relative mortality and morbidity risks associated with exposure to environmental tobacco smoke.

Insofar as industrial and other blue collar workers are more likely to bring home toxic materials on their person, and also are more likely to smoke than those in other occupations, members of a household are more likely to be subject to paraoccupational exposure and belong to lower socioeconomic strata if the household contains a smoker than if the household does not contain a smoker. Thus observed differences in risk of mortality or morbidity ascribed to ETS on the basis of a comparison of households with and without smokers may be partly or entirely due to differences in paraoccupational exposure and socioeconomic strata. Similarly, differences in mortality and morbidity ascribed to paraoccupational exposure may be partly or entirely due to differences in ETS exposure that are also related to social class and to types of occupation.

A critical examination of OSHA's assessment of risk associated with workplace exposure to environmental tobacco smoke.

In response to a request for information on indoor air quality problems, the U.S. Occupational Health and Safety Administration (OSHA) has proposed a rule addressing indoor air quality in general, and especially environmental tobacco smoke (ETS), in indoor work environments.

Correcting standardized rate ratios for imprecise classification of a polychotomous exposure variable with limited data.

The analysis of exposure misclassification has received considerable attention in the epidemiologic literature, with the result that methods for correcting many summary risk estimates for such misclassification are well known. However, the application of such methods typically requires more data than are usually published (for example, the complete set of exposure- and age-specific mortality rates). The authors show, under the assumption that exposure misclassification occurs independently of disease status and confounder level, that it is possible to obtain estimates of standardized rate ratios corrected for a given pattern of misclassification from only the published standardized risk ratios and the misclassification matrix.

Mortality from respiratory cancers (including lung cancer) among workers employed in formaldehyde industries.

A joint study on effects of formaldehyde exposure in industrial populations by the National Cancer Institute and the Formaldehyde Institute, Inc. (Blair et al. [1986]: J Natl Cancer Inst 76: 1071-1084; Blair and Stewart [1989]: J Occup Med 31: 881, Blair et al.

Comments on the Health Effects Institute-Asbestos Research (HEI-AR) report: "Asbestos in public and commercial buildings," with emphasis on risk assessment methods used.

A Health Effects Institute--Asbestos Research Report calculates the risk of exposure to environmental asbestos fibers (EAF) by downward extrapolation from the mortality of workers exposed for 20 years. This extrapolation is improper because 1) relative risks of asbestos exposure very likely are not linearly progressive; 2) the composition of EAF may not be equivalent to that in mining or fabricating; 3) the same environmental asbestos concentration probably represents different exposure doses for different populations; and 4) health effects of asbestos exposure on children, seniors, patients, the institutionalized, the handicapped, and the chronically ill may not be the same as those of healthy workers. Evidence of asbestos-related disease among family members of exposed workers demonstrates that the risk observed for EAF is substantially larger than that estimated from downward extrapolation and suggests a basis for an alternative approach to estimating asbestos-related health risks.

Income, race, and mortality.

This study was undertaken to clarify the complex relationship between poverty and race with disease-specific mortality. Data from the 1987 National Health Interview Survey and the 1986 National Mortality Followback Survey were used to estimate standardized mortality ratios (SMRs) for various categories (all causes, all cancers, noncancerous medical causes, lung and breast cancers, ischemic heart disease, and cerebrovascular disease) associated with income below the poverty line and were compared with those with adequate or better than adequate income. All SMRs were substantially elevated.

Risk attribution and tobacco-related deaths.

The number of deaths that would not have occurred had an exposure or trait been absent is generally estimated by observing mortality rates in sample populations of exposed and nonexposed persons and applying them to the population of interest. Three methods used to estimate deaths due to tobacco use are evaluated. Each method requires estimates of certain absolute and relative risks, and the published estimates based on them assume that the absolute and relative risks observed in the two large American Cancer Society prospective studies can be applied to the US population or to populations in developed countries.

Computation of relative risk based on simultaneous surveys: an alternative to cohort and case-control studies.

If the same information on the distribution of risk factors is available for both the general population and a subset distinguished by some disease outcome, it becomes possible to derive relative risk estimates applicable to the entire population with the assurance that the data upon which the estimates are based is representative of that population. To illustrate this approach, data from the 1986 National Mortality Follow-back Survey and the 1987 National Health Interview Survey were used to compute rate ratios for several causes of death for work in dirtyier as compared with cleaner occupations by three methods commonly employed in cohort and case-control studies: the usual standardized rate ratio, the Mantel-Haenszel estimate of the rate ratio, and a multiplicative model fit to an appropriate cross-classification. Properly placed questions in appropriate surveys might very well serve as a substitute for cohort studies and could be performed at less cost and with less overall effort, and completed in a shorter time.

Analysis of the relationship between smokeless tobacco and cancer based on data from the National Mortality Followback Survey.

This study investigates the potential link between the use of smokeless tobacco and oral cancer and cancer of digestive organs. The combined data of the National Mortality Followback Survey (NMFS), a probability sample of the U.S.

Bias in the attribution of lung cancer as cause of death and its possible consequences for calculating smoking-related risks.

Most published calculations of mortality risk, especially those for lung cancer associated with smoking, are based almost exclusively on the underlying cause as recorded on death certificates. Such risk calculations implicitly assume that the conditional probability of recording lung cancer as the underlying cause of death, given that it really is the underlying cause, is the same for all exposure groups. If these probabilities are not equal for all exposure groups, we call the resulting bias a cause of death attribution bias.

A graphical approach to the interpretation of age-period-cohort data.

Two major obstacles to the routine application of age-period-cohort models are (1) the identification problem, and (2) the fact that separate interpretation of the coefficients of the model is seldom possible. We offer a practical solution to these obstacles that involves plotting the relation between the variable of interest and the age, period, and cohort variables in such a manner that nontrivial age, period, or cohort effects are readily recognized as particular types of features in the graph. These features remain recognizable in the presence of normal sampling variability.

A practical approach to estimating the true effect of exposure despite imprecise exposure classification.

Accurate information on actual exposure to some possibly toxic agent usually is not available in long-term occupational studies. Any strategy for assigning exposure levels or categories necessarily results in misclassification, where some individuals classified as exposed have no real exposure and some individuals classified as not exposed have some exposure to the agent. Both misclassification errors serve to reduce the estimate of risk associated with exposure.

The confounding of occupation and smoking and its consequences.

A strong pattern in smoking behavior can be demonstrated, in which smoking is much more prevalent among those occupational groups (and social strata) that are also more exposed to hazards in the workplace and much less prevalent among those groups less exposed to such hazards. As a consequence, comparing individuals with greater to those with lesser exposure to tobacco also compares groups that differ with respect to occupational exposure to dust, fumes and toxic substances and with respect to occupationally related lifestyle factors. Analyses of the U.

The sick person effect.

Very often criteria by which subjects are selected for epidemiological studies are associated in some manner with their health. The Healthy Worker Effect (HWE) or Healthy Person Effect (HPE) is well known. Little has been said about the converse case in which selection is associated with decreased health status, the Sick Person Effect (SPE).

Age related changes in age of starting to smoke.

The Average Age of Starting to Smoke (AASS) has been reported to decline for younger birth cohorts. That apparent decline has been used to support a conclusion of an increase in smoking among younger individuals. However, in some cases the apparent decline is an artifact of the method of computation which arises when the quantity being averaged is related to a quantity used to classify subjects for comparison.

Comparison of smoking-related risk factors among black and white males.

The lung cancer risk factors of smoking prevalence, amount smoked, and age started to smoke were compared for blacks and whites, using the 1970 and 1979/80 National Health Interview Survey (NHIS) survey data. For both survey years, proportionally more blacks were never smokers and fewer were ever smokers (although more were current and fewer former smokers). The average adult black smoker smoked approximately 65% of the number of cigarettes smoked by the average white adult.