Upper gastrointestinal adverse events and cyclical etidronate

PURPOSE

Recently, there have been several published case reports of esophagitis associated with the use of aminobisphosphonates. The objective of this study was to evaluate the upper gastrointestinal (GI) safety of cyclical etidronate, an alkylbisphosphonate, in routine clinical practice.

PATIENTS AND METHODS

Information was obtained from 550 general practices in the United Kingdom that provide the medical records to the General Practice Research Database. A group of 7977 cyclical etidronate takers and 2 age-, gender-, and practice-matched control groups (1 with osteoporosis and 1 without) were analyzed.

RESULTS

For cyclical etidronate takers, the average age was 71.6 years and total follow-up was 10,328 person-years. The risk of upper GI events (inflammation or ulcer of esophagus, stomach, or duodenum) was comparable between patients taking etidronate and the two control groups. The adjusted relative risk of upper GI events was 0.92 (95% confidence interval [CI] 0.78 to 1.09) for etidronate takers compared with osteoporosis controls and 1.12 (CI 0.91 to 1.37) compared to nonosteoporosis controls. For esophagitis and esophageal ulcers, the relative risks were 0.83 (CI 0.64 to 1.08) and 0.97 (CI 0.71 to 1.31) respectively. The incidence of upper GI events during nonsteroidal anti-inflammatory drug (NSAID), aspirin, or corticosteroid use was similar across the three groups. The upper GI risks of etidronate NSAID users were 0.71 (CI 0.45 to 1.11) and 2.06 (CI 0.98 to 4.35) compared with NSAID users in the two control groups.

CONCLUSIONS

These results support the GI tolerability and safety profile of cyclical etidronate in routine clinical practice. Concomitant use of cyclical etidronate with NSAIDs, aspirin, or corticosteroids did not increase the incidence of upper GI events.

Determinants of initiation and suboptimal use of anti-ulcer medication: a study of the Quebec older population

OBJECTIVES

To describe the use of anti-ulcer medication in the Quebec older population; to examine determinants of initiation, suboptimal use, and switches between products.

DESIGN

Population-based retrospective cohort study.

SETTING

Universal health program for older adults in Quebec.

PARTICIPANTS

5000 users and 5000 non-users of anti-ulcer medications were selected randomly. Use was defined as the presence in the 1991 prescription database of an anti-ulcer prescription. Among users, 1697 (34%) were new users and were considered as the exposure group. Subjects were followed for 365 days after inclusion.

MEASUREMENTS

Measured were patient's age, gender, prescribed duration of anti-ulcer medication, concomitant medications, and gastrointestinal diagnostic procedures.

RESULTS

A total of 17% of new users had unusually short courses; 18% were long-term users. There was no difference in duration for omeprazole compared with other anti-ulcer medications. First-time use of NSAIDs was the strongest predictor of initiation of anti-ulcer medication (odds ratio = 3.21; 95% CI, 2.66-3.88). Twenty-six percent of users switched brands. Only 9.5% of new users underwent a diagnostic procedure before initiation of therapy, and 49% of long-term users ever underwent such procedure.

CONCLUSION

Despite a relatively homogeneous recommended duration of therapy, patterns of use of anti-ulcer medication among older people are highly variable, and treatment is often not accompanied by a diagnostic procedure.

Rates of hypoglycemia in users of sulfonylureas

OBJECTIVE

To identify the demographic and clinical characteristics of sulfonylurea users. To assess the risk of hypoglycemia in patients treated with sulfonylureas in clinical practice, and to characterize the risk in relation to the different drugs used.

RESEARCH DESIGN AND METHODS

A cohort of 33,243 sulfonylurea users chosen from 719 clinical practices in the United Kingdom were identified through the VAMP-Research database. Information on demographic characteristics, medical diagnoses and use of medical services was obtained through the computerized records. For a stratified sample of 500 patients, general practioners completed a structured questionnaire on the duration, treatment, and complications of diabetes mellitus, obesity, alcohol use, and smoking history. Patients with a diagnosis of hypoglycemia, as recorded in the database within a time-window of a sulfonylurea prescription, were identified. Incidence rates per person-year of sulfonylurea therapy were estimated.

RESULTS

Other than a longer duration of diabetes in users of chlorpropamide, no differences were observed among users of different sulfonylurea agents with respect to diabetic complications, adequacy of diabetic control, obesity, smoking, and excessive alcohol consumption. A diagnosis of hypoglycemia during sulfonylurea therapy was recorded in 605 people over 34,052 person-years of sulfonylurea therapy, which converted into an annual risk of 1.8%. The risk in glibenclamide users was higher than in users of other types of sulfonylureas uses. Duration of therapy, concomitant use of insulin, sulfonylurea-potentiating or antagonizing and concomitant use of beta-blockers were predictive of the risk of developing hypoglycemia.

DISCUSSION

Drug use patterns showed comparability among users of different sulfonylurea agents. Our findings suggest that the rate of diagnosis of hypoglycemia made by physicians is higher for glibenclamide than for other sulfonylureas. An epidemiological study with objectively diagnosed hypoglycemia should be undertaken to confirm these results.

The VEINES study (VEnous Insufficiency Epidemiologic and Economic Study): an international cohort study on chronic venous disorders of the leg. VEINES Group

The aim of the VEINES study is to address some gaps in knowledge regarding the multidimensional repercussions of venous disorders and the measurement of outcomes. Its objectives are to describe and compare defined clinical presentations of venous-related leg disorders with regard to natural history, clinical outcome, functional capacity, quality of life, and economic impact. A secondary objective is to develop or identify and test standardized instruments for the evaluation of therapeutic effectiveness. This paper presents an overview of the design of the study and of the options chosen for the recruitment process and the outcome measures.

Should the gap be filled between guidelines and actual practice for management of low back pain in primary care? The Quebec experience

STUDY DESIGN

A prospective cohort study.

OBJECTIVES

To describe health services utilization for low back pain in the province of Quebec, Canada, and to compare it with North American guidelines.

SUMMARY OF BACKGROUND DATA

The Quebec Task Force and the Agency for Health Care Planning and Research (United States) published guidelines for the management of low back pain in 1987 and 1994, respectively.

METHODS

A cohort of 2147 adults with low back pain identified at the Quebec Worker's Compensation Board were selected randomly and observed over 2 years' time for their health care utilization profile.

RESULTS

During the study period, 57.8% of the workers still under active care 7 weeks after their back injury had not yet been referred to a specialist. Specialized imaging techniques were obtained by 4.5% of the patients, with a delay of 7 weeks or more in 66% of them. Surgery was performed on 1.6% of the patients. The presence of an initial specific diagnosis and proximity to a university hospital significantly increased utilization rate and reduced the delays.

CONCLUSION

Health services utilization for back pain in Quebec was equal or lower to what currently is practiced elsewhere, but access to specialists was not meeting the current recommendations. This would represent a 12% net increase in new specialist contacts and a quicker access in 39% who saw a specialist. Before such an effort can be considered, health care planners will need a better definition of the role of the specialist consultation in the guidelines and scientific evidence specifically addressing their benefit in primary care, especially in the absence of a specific diagnosis.

Agent orange and the risk of gestational trophoblastic disease in Vietnam

There have been claims of an increased risk for gestational trophoblastic disease (i.e., hydatidiform mole and choriocarcinoma) in Vietnam since the period of Agent Orange sprayings. In 1990, we conducted a case-control study in Ho Chi Minh City to investigate risk factors for gestational trophoblastic disease in Vietnam. Eighty-seven married women, all of whom had a recent pathologic diagnosis of gestational trophoblastic disease, identified in the Obstetrical and Gynecological Hospital, were included in the study. Eighty-seven married women who were admitted mainly in the surgery departments of the same hospital were the controls, and they were matched to cases for age and area of residence. Odds ratios (ORs), adjusted for matching variables and other potential confounders, were estimated with unconditional logistic regression. A statistically significant trend in risk was observed with previous live births (p = .01). Cases were found to eat less meat per wk (OR = 0.4, 95% confidence interval [95% CI] = 0.2-0.9 for > or = five meat dishes) and to own fewer consumer goods than controls. An increase in risk was associated with the breeding of pigs (OR = 5.7, 95% CI = 1.2-27.6 for raising three or more pigs). A cumulative Agent Orange exposure index was constructed, using the patient's complete residence history. No significant difference was found between cases and controls for this index (OR = 0.7, 95% CI = 0.2-1.8 for high-exposure category), nor was such a difference noted for the agricultural use of pesticides.

Appetite-suppressant drugs and the risk of primary pulmonary hypertension. International Primary Pulmonary Hypertension Study Group

BACKGROUND

Recently, a cluster of patients was observed in France in whom primary pulmonary hypertension developed in patients exposed to derivatives of fenfluramine in appetite suppressants (anorexic agents), which are used for weight control. We investigated the potential role of anorexic agents and other suspected risk factors for primary pulmonary hypertension.

METHODS

In a case-control study, we assessed 95 patients with primary pulmonary hypertension from 35 centers in France, Belgium, the United Kingdom, and the Netherlands and 355 controls recruited from general practices and matched to the patients' sex and age.

RESULTS

The use of anorexic drugs (mainly derivatives of fenfluramine) was associated with an increased risk of primary pulmonary hypertension (odds ratio with any anorexic-drug use, 6.3; 95 percent confidence interval, 3.0 to 13.2). For the use of anorexic agents in the preceding year, the odds ratio was 10.1 (95 percent confidence interval, 3.4 to 29.9). When anorexic drugs were used to a total of more than three months, the odds ratio was 23.1 (95 percent confidence interval, 6.9 to 77.7). We also confirmed an association with several previously identified risk factors: a family history of pulmonary hypertension, infection with the human immunodeficiency virus, cirrhosis, and use of cocaine or intravenous drugs.

CONCLUSIONS

The use of anorexic drugs was associated with the development of primary pulmonary hypertension. Active surveillance for this disease should be considered, particularly since their use is expected to increase in the near future.

Physician referral to physical therapy in a cohort of workers compensated for low back pain

BACKGROUND AND PURPOSE

This study described the physical therapy referral of workers compensated for back injury; characterized physical therapy by duration and choice of therapeutic techniques; and compared workers who were and were not referred for physical therapy in terms of age, gender, diagnosis, and absence from work.

SUBJECT

A cohort of 2,147 subjects were randomly selected from 54,401 workers compensated for back injuries in 1988.

METHODS

Each subject was followed for 2 years from date of entry into the study. Data were obtained from the Quebec Worker's Compensation Board computerized files, medical files, and initial reports completed by physical therapists.

RESULTS

Of the cohort, 389 subjects (18%) had received physical therapy after referral by their physician. Exercise, heat, ultrasound, back education, manipulation, and transcutaneous electrical nerve stimulation were the most frequently selected treatments. Implementation of physical therapy within 1 month of back injury had a strong protective effect on return to work within 60 days. Female gender and presence of a specific diagnosis were predictors for greater than 60 days' absence.

CONCLUSION AND DISCUSSION

This study demonstrated that physicians request physical therapy services based on certain patient characteristics. Patients who were referred earlier tended to return to work sooner than those who were referred later, which indicates that timing of physical therapy is an important factor in the rehabilitation of workers with low back pain.

The Quebec Back Pain Disability Scale: conceptualization and development

The Quebec Back Pain Disability Scale is a new measure of functional disability for patients with back pain. Functional disability was operationalized in terms of perceived difficulty associated with simple physical activities. The content of the scale was developed in several stages, including a literature review, two studies seeking the opinions of patients and experts, pilot testing, and a large, longitudinal study of back pain patients. Forty-eight disability items were extensively studied using standard methods such as test-retest reliability, item-total correlations, and factor analysis, as well as modern techniques based on item response theory. Items that were highly effective in discriminating between different levels of disability were selected for the final, reduced scale. The scale has 20 items, representing six empirically derived categories of activities affected by back pain. Measurement properties of this instrument have been previously discussed.

The prognostic consequences in the making of the initial medical diagnosis of work-related back injuries

STUDY DESIGN

A cohort of 1848 workers, representative of all sectors of industry, who were compensated for a low back injury in 1988 but not in the previous 2 years, was followed over 24 months.

OBJECTIVES

To determine the prognostic value of the physician's initial diagnosis of back problems.

SUMMARY OF BACKGROUND DATA

In the absence of a standardized classification of diagnoses of back pain, this study aimed to provide an element of validity to a classification previously proposed that consists of "specific" and "nonspecific" back pain.

METHODS

Medical charts were reviewed at the Quebec Worker's Compensation Board to extract the diagnosis made by the treating physicians within 7 days of the first day of absence from work. Diagnoses were categorized into "specific" (lesions of vertebrae and discs) and "nonspecific" (pain, sprains, and strains). The history of compensated work absence for low back pain in the following 24 months was obtained.

RESULTS

A specific diagnosis was found in 8.9% (165) of the workers, accounting for 31.0% of the patients who accumulated 6 months or more of absence in 2 years. Increasing age and daily amount of compensation also were associated with an increased risk of chronicity.

CONCLUSIONS

The physician's initial diagnosis was highly associated with the risk of chronicity. The explanation for this result is complex, involving the nature of the underlying lesion as well as the impact of the diagnosis "label" on the worker and on the physician-patient relationship.

The Quebec Back Pain Disability Scale. Measurement properties

STUDY DESIGN

The Quebec Back Pain Disability Scale is a 20-item self-administered instrument designed to assess the level of functional disability in individuals with back pain. The scale was administered as part of a larger questionnaire to a group of 242 back pain patients. Follow-up data were obtained after several days and after 2 to 6 months.

OBJECTIVES

The goal of this study was to determine whether the Quebec scale is a reliable, valid, and responsive measure of disability in back pain, and to compare it with other disability scales.

SUMMARY OF BACKGROUND DATA

A number of functional disability scales for back pain are being used, but their conceptual validity is uncertain. Unlike most published instruments, the Quebec scale was constructed using a conceptual approach to disability assessment and empirical methods of item development, analysis, and selection.

METHODS

The authors calculated test-retest and internal consistency coefficients, evaluated construct validity of the scale, and tested its responsiveness against a global index of change. Direct comparisons with the Roland, Oswestry, and SF-36 scales were carried out.

RESULTS

Test-retest reliability was 0.92, and Cronbach's alpha coefficient was 0.96. The scale correlated as expected with other measures of disability, pain, medical history, and utilization variables, work-related variables, and socio-demographic characteristics. Significant changes in disability over time, and differences in change scores between patients that were expected to differ in the direction of change, were found.

CONCLUSIONS

The Quebec scale can be recommended as an outcome measure in clinical trials, and for monitoring the progress of individual patients participating in treatment or rehabilitation programs.

Management of occupational back pain: the Sherbrooke model. Results of a pilot and feasibility study

OBJECTIVES

The aim was to combat occurrence of chronic occupational back pain.

METHODS

A multidisciplinary model to manage back pain that includes both clinical and ergonomic approaches has been developed. Early detection, early clinical and ergonomic evaluations, and early active treatment make up the cornerstone of management. Detection of cases starts after four weeks of absence from work. An ergonomic intervention is implemented at six weeks. A medical specialist is involved at eight weeks. If return to work is not possible after 12 weeks, a functional recovery therapy followed by a therapeutic return to work is implemented. A multidisciplinary team decides if return to original or modified work is possible or if vocational rehabilitation is necessary. This model has been implemented by the investigators in the Sherbrooke (Quebec, Canada) area, and is presently being evaluated through a randomised trial in 31 industrial settlements (about 20,000 workers). A cluster randomisation of industries and workers will allow separate testing of ergonomic and clinical interventions.

RESULTS

One year after implementation, 31 of 35 of the eligible industrial sites participated in the study and 79 of 88 of the eligible workers affected by recent back pain had agreed to participate. Ergonomic and clinical interventions have been implemented as planned. Only three workers dropped out. Hence this global clinical and ergonomic management programme has been shown to be feasible in a general population.

CONCLUSION

A global management programme of back pain joining ergonomic and clinical intervention with a multidisciplinary approach has not been tested yet. Linking these two strategies in a same multidisciplinary team represents a systemic approach to this multifactorial ailment. During the first year of this trial we did not find any conflict between these two interventions from the employer's or worker's point of view.

Evidence of the depletion of susceptibles effect in non-experimental pharmacoepidemiologic research

Past experience with a drug may modify the risk of adverse event associated with current use of this drug. This effect was investigated empirically with a study on non-steroidal anti-inflammatory drugs (NSAIDs)-gastropathy. A hospital-based case-control study was conducted with 244 cases of upper gastrointestinal bleeding (UGIB) age 68 and over and 615 matched controls. Data on all medications dispensed to the study patients during the 3 years preceding admission were obtained from the Quebec universal prescription program automated database. Recent use (within 30 days prior to admission) of non-aspirin NSAIDs increased the risk of UGIB. The estimate of relative risk (RR) was 3.4 (CI, 2.1-5.5). Use of NSAIDs in the previous 3 years was associated with a lower risk of UGIB; the estimate of RR was 0.7 (CI, 0.4-1.0). The estimate of RR for first-time users was 22.7 (2.8-200.0) vs 3.0 (1.9-4.7) for those who had used the drugs at least once in the past 3 years. These results provide empirical evidence of a depletion of susceptibles effect whereby patients who remain on the drugs are those who can tolerate them while those who are susceptible select themselves out of the population at risk. Thus, past use should be considered as a potential risk modifier in non-experimental risk assessment of events associated with drug use.

Correlation between dioxin levels in adipose tissue and estimated exposure to Agent Orange in south Vietnamese residents

To permit new epidemiologic studies of the effects of dioxin on humans in Vietnam, we evaluated a model for quantifying exposure to Agent Orange (exposure index) based on the residential histories of 27 Vietnamese subjects and on information about spraying from the U.S. Army records (Herbs Tape) and compared this index to the dioxin levels measured in the subjects' adipose tissue. The mean dioxin level was 7.8 ppt, and dioxin and furan isomer profiles were similar to those already reported in industrialized countries. In addition, there was a highly significant correlation between the levels of almost all the isomers, whatever their degree of chlorination. For the group of 27 subjects, we found a Pearson correlation coefficient of 0.36 (P = 0.07) between the dioxin levels and the exposure index after log-transformation of both variables. When the analysis was restricted to the 22 subjects with a positive exposure index, the Pearson correlation coefficient rose to 0.50 (P = 0.02). We conclude that despite the limitations and power conditions of the study, this result is encouraging because it will be useful for future epidemiologic studies in Vietnam.

Sample size calculations for single group post-marketing cohort studies

In pharmacoepidemiology, single group cohort is the most frequently proposed design to determine if the incidence rate of an adverse drug reaction among the exposed differs from a reference value. In many situations, the number of events expected in the cohort is too small to conduct sample size calculations based on the normal distribution. This paper proposes, for a single group cohort study, calculations and tables derived from the Poisson distribution. The results are based on a one-sided test with a 0.05 significance level and a power of 0.9 and 0.8. Two parameters have to be specified a priori: the expected incidence of the event under the null hypothesis and the minimum risk ratio to be detected. The required sample size and the critical number of events to reject the null hypothesis are directly derived from the tables. Results show that the normal approximation may lead to an underestimation of the required sample size.

A study of the effects of exposure misclassification due to the time-window design in pharmacoepidemiologic studies

This paper considers the effects of the time-window design on the validity of risk estimates in record linkage studies. A time-window constitutes the number of exposure days assigned to each prescription, often fixed time-intervals. Prescription information was drawn from 36 Dutch pharmacies. Persons, assuming full compliance to the dosage regimen, used NSAIDs during 58% of the 30 day window time (31% with 90 day window). This proportion ranged from 51 to 81% for different NSAIDs; from 75% for elderly to 35% for younger persons. We observed with longer windows a substantive attenuation of incidence rates of peptic ulcer therapy. Simulations also showed that the assignment of equal windows to groups with different durations of drug use can bias risk comparisons, either away from the null or towards the null. We concluded that the choice of prescription time-windows can influence the estimates of exposure risks. Time-windows should cover the period with potential excess risk and be validated.

Viral infections and chemical exposures as risk factors for hepatocellular carcinoma in Vietnam

A case-control study investigating risk factors for hepatocellular carcinoma (HCC) was conducted in Hanoi, in the north of Vietnam, between 1989 and 1992. Male cases of HCC (152) diagnosed in 2 hospitals were included. Hospital controls (241) admitted mainly to abdominal surgery departments were frequency-matched to cases for sex, age, hospital and place of residence (Hanoi, province). Odds ratios adjusted for matching variables and other potential confounders were estimated using unconditional logistic regression, or exact non-parametric statistical inference when numbers were small. Positivity for hepatitis B surface antigen (HBsAg) was the main risk factor for HCC in this sample. Five subjects (3 cases, 2 controls) had been infected by hepatitis C virus (HCV), and none of them were carriers of HBsAg, giving an OR of 38 associated with HCV infection among HBsAG-negative subjects. Alcohol drinking was associated with HCC and interacted with HBsAg positivity. Agricultural use of organophosphorous pesticides (30 liters/year or more) and military service in the south of Vietnam for 10 years or more were also associated with an increased risk of HCC. This study confirms the major role played by HBV infection and its association with HCC in south-east Asia. It also suggests how other factors such as alcohol consumption or exposure to chemicals may interact with HBV infection.

Monitoring of drug utilization in public health surveillance activities: a conceptual framework

The surveillance of individual and aggregate patterns of prescribed medication can potentially provide some very useful information to those involved in public health. At present however, this activity has attracted relatively little attention in Canada. This article will introduce a conceptual framework with which to examine the possibilities of prescription drug monitoring as a tool for public health surveillance. The sources of data available to undertake this activity as well as their limitations, will be presented along with some recent concrete applications.

Twenty years of randomized clinical trials of manipulative therapy for back pain: a review

Manipulative therapy has been one of the most intensively studied approaches to back pain management. This paper reviews 20 years of randomized clinical trials of manipulative therapy, and addresses the following issues: for what condition were these patients treated? What was the population studied, and were workers included? Was a specific technique, spinal manipulation, or a more global approach the object of the trial? Finally, were there long-term outcome measures? The 21 randomized clinical trials reviewed here provide some indication that manipulative therapy offers some positive short-term results; it is not clear at this point whether long-term effects of the treatment have been adequately evaluated. Lack of specificity in the description of samples makes it impossible to conclude on the benefit of spinal manipulation for workers. Whether manipulation is solely responsible for the changes mentioned in these studies, independently of the global approach put forth by its practitioners, is also an open question that awaits further study.

The evolution of compensated occupational spinal injuries. A three-year follow-up study

This study was undertaken to follow up an incidence rate study of spinal injuries carried out from a cross-sectional random sample consisting of 2,342 workers who were compensated at least once in the year 1981 by the Quebec Worker's Compensation Board (QWCB) for an absence from work. These workers were followed for 3 years using the QWCB information system to record any recurrence of compensated absence from work. A total of 850 (36.3%) had at least one recurrence, and had longer episodes of absence than those without a recurrence (P less than 0.0001). Of these 850 workers, 824 (96.9%) had less than five recurrences and showed a systematic trend of gradual increasing duration of absence on each subsequent recurrence (P less than 0.05 in a repeated measures analysis of variance). A positive relationship was found between the duration of the initial episode of absence from work and the subsequent history of absence from work, both in terms of risk of recurrence (P less than 0.001) and of cumulated absence from work (P less than 0.0001), after controlling for age, sex, and site of symptoms. The computed instantaneous risk of entering a recurrence in a 31 year-old man experiencing lumbar symptoms, was 19.9% (95% confidence interval = 19.8-19.9) in the year following an initial episode of one day duration, and 26.7% (95% confidence interval = 24.3-29.3) after an initial episode of 6 months.

Study of civilian victims of terrorist attacks (France 1982-1987)

The medical and psychological consequences of terrorism were assessed through an epidemiologic survey of 254 survivors of terrorist attacks (TA) that occurred in public places in France between 1982 and 1987 (20 bombings and 1 machine-gun attack). Physical lesions were typical of bombings (blast syndrome, burn, coma), but amputations were rare. Post-traumatic stress disorder (PTSD) was present in 10.5% of uninjured victims, 8.3% of moderately injured and 30.7% of severely injured ones. Major depression was found in 13.3% of all victims, with no difference according to the level of the injury. Prevalence rates were not different in males and females, nor did they vary with age of the victim. The prevalence of PTSD was not associated with the delay between TA and questionnaire completion. These findings suggest the need for including psychiatric assistance in the initial care of TA victims, especially severely injured ones.

Methodological issues for the assessment of clusters of adverse pregnancy outcomes in the workplace: the case of video display terminal users

In this paper, we review the consecutive methodological steps to follow when assessing clusters of adverse pregnancy outcomes (APO) in the workplace and the decisions to be taken at each step. The example of clusters of APO reported in VDT users in 1979 to 1982 is taken to illustrate each point. It appears that the number of "expected-unexpected" clusters of APO in VDT users has been largely overestimated as compared to observations and that this might be due to inadequate choices in the models used.

Links between passive smoking and disease: a best-evidence synthesis. A report of the Working Group on Passive Smoking

We reviewed the toxicologic, clinical, and epidemiologic evidence on the health effects of environmental tobacco smoke (ETS). For each type of exposure to environmental tobacco smoke we have sought articles in the English language reporting studies of effects on human health. Formal criteria that stressed study design, quality of execution and generalizability of results were used to select 116 scientifically admissible reports from over 2,900 articles. We concluded that: (a) there is strong evidence of an association between residential exposure to environmental tobacco smoke and both respiratory illness and reduction of lung function, and also between maternal smoking and reduced birth weight; (b) the weight of evidence is compatible with an association between active maternal smoking during pregnancy and increased infant mortality, and also between residential exposure to environmental tobacco smoke (primarily spousal smoking) and the risk of lung cancer; (c) there is evidence consistent with a relationship between exposure to environmental tobacco smoke in the workplace and respiratory symptoms, (d) the evidence is insufficient to implicate residential exposure to environmental tobacco smoke in relation to other forms of malignant disease or congenital malformations; (e) there is no evidence in the literature of an association between nonresidential exposure to environmental tobacco smoke and any form of cancer. Further studies are required to address the effects of exposure to environmental tobacco smoke, especially nonresidential exposure, in carcinogenesis and as a risk factor for atherosclerosis. Further work is also needed to improve measurement of exposure in such studies and to assess the importance of confounding factors.