A meta-analysis of cohort studies describing mortality and cancer incidence among chemical workers in the United States and western Europe.

We evaluated the mortality and cancer experience of employees of the chemical industry in the United States and western Europe, as reported in the peer-reviewed literature between 1966 and 1997 (>1 million workers and >15 million person-years). Cohort studies (N = 461) were grouped (N = 181) so that specific populations could be traced from the earliest to the most recently published report, and we extracted observed and expected numbers of cases for each of 35 mortality and 23 cancer incidence endpoints. We then generated standardized mortality ratios or standardized incidence ratios and 95% confidence intervals, and undertook meta-analyses of subcohorts (for example, gender, latency, or duration of employment), as well as the entire cohort. With few exceptions, the observed cause-specific mortality and site-specific cancer incidences were reassuring: overall, 10% fewer deaths were observed than expected. Fewer than expected deaths from all causes, cardiovascular disease, noncancer respiratory disease, cirrhosis of the liver, and external causes were observed, some or all of which may be attributed to a "healthy worker effect." Meta-analyses revealed weak to moderate excesses of lung and bladder cancers likely caused by occupational exposure to known human carcinogens. We also observed a 10-15% increase in lymphatic and hematopoietic cancers. Additional research is required to gain a more complete understanding of the potential role that methodology and environmental or occupational influences may play in these associations.

Methodologic considerations in estimating burden of disease from environmental risk factors at national and global levels.

Evidence from environmental burden-of-disease studies can provide valuable input in the decision-making process in environmental health, facilitating priority setting and cost effectiveness evaluation. This paper discusses important aspects of environmental burden-of-disease estimates in the light of) published examples. To produce reliable and comparable burden-of-disease estimates for environmental and occupational risk factors, harmonized methods are needed. Such methods should address the feasibility of data collection at national, regional, and global levels, the reliability of estimates, the uncertainty around estimates, and scenario tools to investigate the health gains of options for preventive action in different domains of policy. Any such method will require a framework (i.e., causal inference model) able to take into account the contributions of distal and proximal causes, and the possible interactions between risk factors.

Classification of cardiorespiratory fitness without exercise testing.

PURPOSE: We examined the ability of a nonexercise based VO2max, prediction model to classify cardiorespiratory fitness (CRF) in a population of men and women aged 19-79 yr of age (N = 799). METHODS: A VO2max (mL.kg(-1).min(-1)) prediction model was developed in the study group using multiple linear regression from the independent variables age, age2, gender, physical activity status, height, and body mass. The classification accuracy of this model was examined by cross-tabulating age and gender specific quintiles of measured and predicted CRF. RESULTS: Overall classification accuracy of the model was modest (36%); however, 83% of all subjects were either classified correctly or within one quintile of measured CRF. Extreme misclassification (e.g., misclassifying a low fit individual as high fit) was only rarely observed (0.13%). CONCLUSIONS: The present results support the concept that CRF prediction models can be used to reasonably characterize the fitness level of a cohort using data that can be obtained from a questionnaire. Accordingly, predicted CRF values may be useful as an exposure variable in large epidemiologic studies in which exercise testing is not feasible.

Empirical comparisons of proportional hazards, poisson, and logistic regression modeling of occupational cohort data.

This research was conducted to examine the effect of model choice on the epidemiologic interpretation of occupational cohort data. Three multiplicative models commonly employed in the analysis of occupational cohort studies--proportional hazards. Poisson, and logistic regression--were used to analyze data from an historical cohort study of workers exposed to formaldehyde. Samples were taken from this dataset to create a number of predetermined scenarios for comparing the models, varying study size, outcome frequency, strength of risk factors, and follow-up length. The Poisson and proportional hazards models yielded nearly identical relative risk estimates and confidence intervals in all situations except when confounding by age could not be closely controlled in the Poisson analysis. Logistic regression findings were more variable, with risk estimates differing most from the proportional hazards results when there was a common outcome or strong relative risk. The logistic model also provided less precise estimates than the other two. Thus, although logistic was the easiest model to implement, it should be used only in occupational cohort studies when the outcome is rare (5% or less), and the relative risk is less than approximately 2. Even then, the proportional hazards and Poisson models are better choices. Selecting between these two can be based on convenience in most circumstances.

A multi-city community based smoking research intervention project in the african-american populatio.

OBJECTIVE: To carry out a community-based research approach to determine the most effective educational interventions to reduce smoking among African-American smokers. The intervention included preparation of the community, planning and developing a model of change, and developing a community-based intervention. The study population consisted of 2,544 randomly selected adult African-American smokers residing in four sites in the northeastern and southeastern parts of the United States. The research design provided a comparison of active intervention sites with passive control sites as well as low income and moderate income areas. MAJOR OUTCOME MEASURES: Point prevalence of non-smoking at the time of interview; Period prevalence of non-smoking at the time of interview; Period prevalence of quit attempts in the prior six months; Number of smoke-free days in the prior six months; Number of cigarettes smoked daily at the time of interview. RESULTS: Based upon a survey eighteen months after baseline data was collected, all four measures of cigarette smoking behavior showed a strong statistically significant reduction of personal smoking behavior among those receiving active interventions versus the passive group. On the basis of process variable analysis, direct contact with the project staff in the prior six months was significantly higher in the active intervention areas. There was only a small non-significant increase in personal smoking behavior in moderate income groups as opposed to low income groups. CONCLUSION: An analysis of process variables strongly suggests that, within this African-American Community, "hands on" or "face to face" approaches along with mass media, mailings, and other less personal approaches were more effective in reducing personal smoking behavior than media, mailings, and other impersonal approaches alone addressed to large audiences.

An epidemiological perspective on environmental health indicators.

There is a great amount of ongoing discussion about the need to develop new ways to assess and monitor a population's disease susceptibility to environmental factors. The ultimate goal in developing these tools, called environmental health indicators, is to increase the public health community's capacity for implementing interventions to prevent disease. Much of the discussion focuses on the requirement that the indicators be relatively easy and quick to apply. However, in the rush to find useful existing indicators, or to develop new ones, there is the danger that certain other important attributes of the indicator may be overlooked. These include: (a) whether the indicator truly represents an underlying causal relationship between an environmental exposure and a health consequence; and (b) whether the proposed indicator is a reasonably valid estimate of the underlying causal factor. This article provides a framework for relating environmental health indicators to the methods of epidemiology including some guidance for selecting and evaluating the appropriateness of proposed environmental health indicators. Examples are given which demonstrate how environmental health indicators can lead to a biased interpretation of underlying associations between environmental factors and the potential for disease when they are improperly conceived. These problems can be avoided by employing routine epidemiological concepts and methods as indicators are developed and evaluated.

Survey of methods and statistical models used in the analysis of occupational cohort studies.

OBJECTIVES: This survey was conducted to determine the frequency with which different data analysis techniques are being used in occupational cohort studies. Of particular interest was the relative use of external and internal comparison groups, and the choice of multivariable model. METHODS: Occupational cohort studies published in 1990-91 were located with Medline and Index Medicus, and the contents of several relevant journals were systematically reviewed. Each study was categorised by the methods of external or internal comparisons performed. RESULTS: Of 200 occupational cohort studies identified, 104 (52%) conducted only external comparisons, 46 (23%) conducted only internal, and 50 (25%) presented both. Of those that used an external referent population, about two thirds used a national standard. 40 of the studies that performed internal comparisons fitted multivariable models, with use divided about equally between proportional hazards regression, Poisson regression, and logistic regression. DISCUSSION: The finding that logistic regression is used quite commonly, even though it does not directly model time dependent data of the type frequently encountered in occupational cohort studies, was suprising. The reasons why investigators choose from among the available statistical and modelling techniques are likely to include familiarity, ease of use, restrictions in study population characteristics, especially study size, and others. Authors should be encouraged to be more explicit about the statistical methods used in the analysis of occupational cohort studies, as well as whether important assumptions about their data have been evaluated.

A retrospective-cohort study of occupational exposure to hexavalent chromium.

A retrospective cohort study was conducted to examine the risk of mortality, cancer, and other adverse health outcomes, at the United States' largest chromate chemicals manufacturing facility in Castle Hayne, North Carolina. This facility, built in 1971, was designed to reduce the high levels of chromium exposure found at most older facilities. Exposure assessment was based on analysis of more than 5,000 personal breathing zone samples collected over a 15-year period. A questionnaire was used to collect relevant occupational, medical, smoking, and other information from current and former employees. Analysis of the cohort's mortality experience found no substantial departures from that expected based on external comparisons, although evidence of a healthy worker effect was observed. Internal cohort analyses were limited by relatively small numbers; however, a subgroup of employees who transferred from older facilities was found to have higher risks of mortality (odds ratio = 1.27 for each 3 years of previous exposure; 90% confidence interval (CI) = 1.07-1.51) and cancer (odds ratio = 1.22 for each 3 years of previous exposure; 90% CI = 1.03-1.45). While this subgroup represented only 11% of the individuals in this study, they accounted for 46% (6/13) of all observed cancers (excluding skin cancers) and 60% (3/5) of lung cancers. There was no increased risk of mortality or cancer among employees who worked only at the newer facility. As an etiologic research study, the results are limited by the relatively small number of subjects and short follow-up; nevertheless, the findings can be used to design and implement a prospective surveillance system for monitoring the health of chromate production workers.

Managing measurable and perceived risk in the occupational setting.

The occupational health clinic frequently has an important role to play in the communication of workplace risks to employees. Effective communication can be facilitated through a clear understanding about the nature and amount of actual risk. Unfortunately, epidemiologists and other health researchers are often reluctant to interpret the quantitative measures of risk that they report in their studies. This article describes various epidemiological risk measures including measures of disease frequency, measures of disease association with exposure, interaction, and measures of attributable risk, and how they are derived. Recommendations for effective risk communication are given.

An epidemiologic study of sports and weight lifting as possible risk factors for herniated lumbar and cervical discs. The Northeast Collaborative Group on Low Back Pain.

The associations between participation in several specific sports, use of free weights, and use of weight lifting equipment and herniated lumbar or cervical intervertebral discs were examined in a case-control epidemiologic study. Specific sports considered were baseball or softball, golf, bowling, swimming, diving, jogging, aerobics, and racquet sports. Included in the final analysis were 287 patients with lumbar disc herniation and 63 patients with cervical disc herniation, each matched by sex, source of care, and decade of age to 1 control who was free of disc herniation and other conditions of the back or neck. Results indicated that most sports are not associated with an increased risk of herniation, and may be protective. Relative risk estimates for the association between individual sports and lumbar or cervical herniation were generally less than or close to 1.0. There was, however, a weak positive association between bowling and herniation at both the lumbar and cervical regions of the spine. Use of weight lifting equipment was not associated with herniated lumbar or cervical disc, but a possible association was indicated between use of free weights and risk of cervical herniation (relative risk, 1.87; 95% confidence interval, 0.74 to 4.74).

An epidemiologic study of non-occupational lifting as a risk factor for herniated lumbar intervertebral disc. The Northeast Collaborative Group on Low Back Pain.

An epidemiologic case-control study of herniated lumbar intervertebral disc was conducted in Springfield, Massachusetts, New Brunswick, New Jersey, and New York, New York, to evaluate the role of several possible risk factors in the etiology of this disorder. Patients with signs and symptoms of herniated lumbar disc (N = 287) were matched to control subjects without back pain by age, sex, source of care, and geographic area. Of the total case-subject group, 177 were confirmed by surgery, computed tomographic scan, myelogram, or magnetic resonance imaging. This article focuses on non-occupational lifting, an activity not previously reported on. Frequent lifting of objects or children weighing 25 or more pounds with knees straight and back bent was associated with increased risk of herniated lumbar disc. This association was particularly strong among confirmed case subjects (relative risk = 3.95). Positive associations among confirmed case subjects were also seen for frequent lifting with arms extended (relative risk = 1.87) and twisting while lifting (relative risk = 1.90). No associations were found for frequent stretching or carrying. If confirmed in other investigations, these data suggest that instruction in lifting techniques should be extended into the home.

Comparison of sufentanil, bupivacaine, and their combination for epidural analgesia in obstetrics.

BACKGROUND AND OBJECTIVES: We postulated that epidural sufentanil alone would provide adequate analgesia for labor and delivery. We also considered the possibility that a combination of epidural sufentanil and bupivacaine would demonstrate superior analgesia and fewer side effects when compared with either agent alone. METHODS: Using a randomized, double-blind design, parturients were prospectively assigned to receive intermittent 10-ml doses of 3 micrograms/ml sufentanil in saline (Group S), 1.5 micrograms/ml sufentanil in 0.125% bupivacaine (Group SB), or 0.25% bupivacaine (Group B). Lumbar epidural catheters were placed during the first stage of labor, and a test dose (3 ml 2% lidocaine with 15 micrograms epinephrine) was given, followed by coded study solution. Subsequent doses of study solution were given at the patient's request. Those parturients who remained uncomfortable after 30 minutes were given 10 ml 2% lidocaine and were designated efficacy failures. Patients were evaluated for quality and duration of analgesia for each dose. Neonates were assessed using Apgar scores and the neonatal behavioral assessment scale. Maternal and umbilical venous sufentanil concentrations were measured at the time of delivery. RESULTS: All patients received satisfactory analgesia of similar duration after the first epidural dose. After subsequent doses, women in Group S experienced more efficacy failures (Groups S, SB, and B, respectively, 12 of 26, 5 of 22, and 1 of 25; p less than 0.005) and received briefer, less intense analgesia compared to the other groups. Instrumental delivery was performed more frequently for women in Group B (Groups S, SB, and B, respectively, 0 of 14, 2 of 17, and 7 of 24; p = 0.04). No serious maternal side effects occurred. Apgar and neurobehavioral scores were comparable for all groups, with the exception that Group B infants had higher irritability scores at 1 hour of age (p = 0.003). Neither maternal nor umbilical venous sufentanil concentrations bore a consistent relationship to clinical outcomes. CONCLUSIONS: Epidural sufentanil alone does not reliably provide satisfactory analgesia for labor and delivery. Addition of small amounts of local anesthetic to bolus doses of sufentanil enhances and prolongs the analgesic effect.

Case-control studies in pediatric epidemiology: parent surrogates and potential pitfalls of inaccurate and selective recall.

The case-control study is quite popular as a study design for exploring associations between risk factors and disease in pediatric epidemiology. Since data concerning exposures to the child are often collected through interviews with parents or other surrogates, researchers should be aware of the opportunities for bias due to inaccurate or incomplete recall. Methods which exist for the control of this problem are presented. These include: the selection of control groups with childhood conditions of similar etiologic uncertainty as the disease being studied; collecting exposure data from both parents; collection of data from children where possible; diligent interviewer training; reviewing clinical records; and use of validity scales. Strengths and weaknesses of these strategies are discussed.

City directories as sources for survey work in low- and middle-income black communities.

Commercial directories and governmental lists of dwelling units in low income urban Black communities in four eastern cities were evaluated for completeness. With rare exceptions, less than 90 percent of dwelling units were included in any one list and no list adequately identified multiple dwelling unit structures. Since household income is likely to be lower among households in such structures, all lists tend to miss the very poor, i.e., those who may be at highest health risk.