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There has been some suggestion that men first hired during World War II do not show the typical healthy worker effect and may have been more unhealthy than their counterparts who entered military service. We have studied 41,000 workers at six plants to determine whether men hired during World War II had higher mortality than men hired just before or after WWII. No evidence was found of any "unhealthy WWII worker" effect.
A respiratory health survey was conducted in a grain mill and the relationship of health indicators to quantitative measures of airborne dust, fungal, and bacterial contamination was examined. Respiratory symptoms were more prevalent in the high dust exposure categories; lung function levels were also higher in the high dust exposure categories, consistent with a "healthy" worker effect. Workers in the three higher dust exposure categories showed either no change or a decrease in lung function over the working week, while workers in the low exposure category demonstrated an improvement in lung function over the working week. Total dust and microbiological (fungal and bacterial) load were found to be significantly related to each other, and the relationship of microbiological load to lung function level and changes over the working week were similar to those found for total dust.
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.
Mortality among workers with 2 or more years employment at an automotive stamping and assembly complex was analyzed using standardized mortality ratio (SMR), proportional mortality ratio (PMR), and mortality odds ratio (MOR) methods. The stamping plant all-cause SMR was considerably less than expected (for white men, SMR = 0.65, 95% confidence interval [CI] = 0.54, 0.79; for black men, SMR = 0.73, 95% CI = 0.45, 1.13), indicating a strong "healthy worker effect." However, six stomach cancer deaths produced an SMR of 4.4 (95% CI = 1.62, 9.6) and a PMR of 6.8 (95% CI = 2.5, 15). Based on small numbers of cases, stomach cancer risk increased with duration in stamping and tool and die departments where exposures included drawing compound and other metalworking fluids. Stamping plant lung cancer mortality was elevated among production welders (MOR = 2.7, 95% CI = 1.2, 6.3), and increased with duration. Welding was performed on sheet metal sometimes coated with drawing compound, primer, or epoxy resin adhesive. As was observed for the stamping plant, the all-cause SMR for the two assembly plants was unusually low (for white men, SMR = 0.64, 95% CI = 0.56, 0.73; for black men, SMR = 0.57, 95% CI = 0.43, 0.75). The lung cancer SMR was not elevated but the MOR was (MOR = 1.58, 95% CI = 1.1, 2.4) and increased with assembly plant duration (MOR = 1.78, 95% CI = 1.02, 3.1, at mean duration of cases). In the assembly plants, paint oven stack emissions had been reintroduced into the plant by the ventilation system.
Epidemiological studies carried out in Great Britain, Scandinavia and the United States indicate that workers exposed to carbon disulfide are at an increased risk for cardiovascular disease (CVD) mortality, and in particular for ischemic heart disease (IHD) mortality. In the epidemiological study reported here a retrospective cohort design was used. The total study population consisted of 3322 workers from a Dutch viscose textile plant who had all been employed for at least half a year between 1 January 1947 and 1 January 1980. Only production and maintenance workers were selected for the study. A group of 1434 workers who had been exposed to carbon disulfide was identified from the files available at the plant. The remaining 1888 workers who had not been exposed to carbon disulfide were used as a reference group. The total study population was followed for mortality until 1 January 1988. For the 762 workers who had died before that date, the causes of death were checked at the Central Bureau of Statistics. The results show a slightly but significantly increased risk for CVD mortality (CVD-specific SMR of 115), despite the observation of the so-called healthy worker effect and the statistical uncertainties inherent to this type of study. The results are in accordance with those reported by other investigators. The results indicate that exposure to relatively low levels of carbon disulfide increases the risk of CVD mortality.
There are many issues in firefighting that involve human factors and cardiopulmonary conditioning. Population-based mortality and disability surveillance studies suggest a relatively small but significant excess of disability but not mortality from nonmalignant cardiovascular disease for firefighters. More targeted cohort and case-control studies do not support such an excess and instead suggest a strong healthy worker effect. Pulmonary function among firefighters has been extensively studied, with contradictory findings. Extreme exposures and long-term exposure in combination with cigarette smoking may be risk factors for respiratory disorders and accelerated decline in airflow. It appears likely that individual firefighters who show early signs of illness are often selectively transferred out of active firefighting positions. Despite exposure to substances such as carbon monoxide that may predispose to cardiovascular mortality and morbidity, excesses are not consistently shown in mortality studies. Clinical studies of individual firefighters do suggest an elevated risk for myocardial ischemia. The ergonomic demands of firefighting are extreme at peak activity because of high energy costs for activities such as climbing aerial ladders, the positive heat balance from endogenous and absorbed environmental heat, and encumbrance by bulky but necessary protective equipment. The psychological stresses of firefighting include long periods of relative inactivity punctuated by highly stressful alarms and extremely stressful situations such as rescues, as reflected in physiological and biochemical indicators. Firefighters are at risk for depression and post-traumatic stress disorder, although morale overall is generally much higher than in comparable occupations. Women firefighter candidates as a group perform less well on selection test simulating the demands of active firefighting, but some individual women perform very well.
A current cohort study aims at estimating the relative risk of incidence of cancer for the personnel of several chemical compagnies in Geneva. The paper discusses some methodological problems encountered, especially with regard to the healthy worker effect.
OBJECTIVES: To examine relationships between shift work and markers (metabolic abnormalities) of insulin resistance (IR). METHODS: A cross-sectional study of 2,824 day and 826 shift workers. All the subjects were male blue-collar workers aged 30-59 years. Four IR markers [(1) hypertension (systolic blood pressure >or=140 mmHg or diastolic blood pressure >or=90 mmHg or under treatment for hypertension); (2) hyperglycemia (fasting serum glucose >or=7.00 mmol/l or under treatment for diabetes); (3) hypertriglyceridemia (fasting serum triglyceride >or=1.70 mmol/l or under treatment for hyperlipidemia); (4) hypo-HDL-cholesterolemia (fasting serum HDL-cholesterol <1.04 mmol/l)] were checked. Subsequently, IR syndrome, a cluster of IR markers, was expediently diagnosed by the number (N) of IR markers found in each worker. N>or=1, N>or=2 or N>or=3 was used as a cutpoint for the diagnosis. The prevalence of each IR marker and IR syndrome was compared between the two worker groups. Age, body mass index (kg/m(2)), job, drinking, smoking, and exercise were used as confounding factors. Job, work schedule and lifestyles were based on self-administered questionnaires. RESULTS: Hypertriglyceridemia (28.7% in day workers, 31.2% in shift workers) was most prevalent (4.6%), and hyperglycemia (5.4%) was least, in the four IR markers in both worker groups. Approximately half of the subjects had at least one IR marker in both groups (N>or=1; 46.0% and 46.6%, respectively). However, a full cluster of IR markers was rare in both groups (N=4; 0.2% and 0.1%, respectively). Prevalence of IR syndrome by any cutpoints increased with age in day workers, but shift workers aged 50 years or older had lower prevalence than shift workers younger than 50 years. In subjects younger than 50 years, all IR markers (except for hypo-HDL-cholesterolemia) and IR syndrome by any cutpoints were more prevalent in shift workers than in day workers. Contrariwise, in subjects aged 50 years or older, lower prevalence of all IR markers and IR syndrome in shift workers than in day workers was found. These results were not influenced by statistical adjustments for the confounding factors by multiple logistic regression analysis. CONCLUSIONS: Shift work may be associated with IR syndrome in workers younger than 50 years. These relations may be underestimated mainly by broad definition of shift work and healthy-worker effects.
OBJECTIVE: The aim of this study was to verify or to disprove whether the term 'Welder's maculopathy' or 'Welding arc maculopathy' has to be considered being a justifiable occupational hazard and is to be annexed to the list of occupational diseases. METHODS: Multifocal electroretinography (MERG) and thorough ophthalmologic examinations were performed in a group of 89 welders. The matched control group comprised 81 subjects who had never been exposed to welding. All participants of this study were examined by a specialist of occupational medicine prior to the MERG. RESULTS: Multifocal electroretinography as well as ophthalmological tests did not reveal a significant morphological or functional differences between the welders and the control group. On an average, the welders' visual acuity appeared to be better than that of the control group. This phenomenon could be attributed to the so-called healthy worker effect. CONCLUSION: Welding arc maculopathy seems to be rather a sequel of occupational accidents and negligence of safety regulations. The results of this study indicate that the usual protective measures in professional welding appears to be sufficient in order to prevent an occupational risk of welding arc maculopathy.
OBJECTIVE: A mortality study on the association between lung cancer and occupational exposure to polycyclic aromatic hydrocarbons (PAHs) was carried out in a French aluminium reduction plant. This study updated a previous mortality study. METHOD: The historical cohort included every male worker who had been employed in the plant for at least 1 year between 1950 and 1994. Workers were followed-up for mortality from 1968 to 1994. Causes of death were obtained from death certificates. Standardised mortality ratios (SMRs) and 95% confidence intervals (CI) were computed using regional mortality rates as external reference to compare observed and expected numbers of deaths, adjusted for gender, age and calendar time. RESULTS: The cohort comprised 2,133 men, of whom 335 died during the follow-up period. The observed mortality was lower than expected for all causes of death (SMR = 0.81, CI 0.72-0.90) and for lung cancer (observed = 19, SMR = 0.63, CI 0.38 0.98). No lung cancer excess was observed in workshops where PAH exposure was likely to have occurred, and no trend was observed according to duration of exposure and time since first exposure. This low lung cancer mortality could be partly explained by a marked healthy worker effect and a possible negative confounding by smoking. An excess was observed for bladder cancer (observed = 7, SMR = 1.77, CI 0.713.64) in the whole cohort, that was higher among workers employed in workshops where PAH exposure was likely to have occurred (observed = 6, SMR = 2.15, CI 0.79-4.68). In addition, an SMR higher than unity was observed for "psychoses and neuro-degenerative diseases" (observed = 6, SMR = 2.39, CI 0.88-5.21), that could not be related to occupational aluminium exposure. CONCLUSION: No lung cancer risk was detected. Non-significant excesses were observed for bladder cancer and for psychoses and neuro-degenerative diseases.
BACKGROUND: Pulmonary function tests may reveal obstructive lung disease with altered forced expiratory volume in 1 s (FEV1) in cotton textile workers. Since 1930, many cohort studies have been performed to assess the disease mortality rate in cotton textile workers. MATERIALS AND METHODS: The authors performed a meta-analysis of the SMR results of these studies. RESULTS: From the meta-analysis, the SMRs were as follows: for all deaths, 0.792 in males and 0.873 in females; for cancers, 0.705 in males and 0.829 in females. DISCUSSION: The male cotton textile workers were healthier than the general population. The healthy-worker effect may be one of the causes, in general workers in industry have a better mortality patterns than those not working.
This study describes the mortality experience in a cohort of 23,401 farmers, residing in southern Piedmont, Italy, and licensed to use pesticides. From 1970 to 1986 the cohort included 340,794 person-years and 2683 deaths were observed. A strong attenuation of the death risk was found due to the healthy worker effect (seen as an active role in the application for the license by the members of the cohort) and due to the limited comparability of the cohort with respect to the reference population. The standardized mortality ratios (SMRs) were remarkably < 100 for all causes (SMR = 59; 95% confidence interval = 57-61) and for all tumors (SMR = 60; 95% CI 55-64), but they increased with the increasing duration of the follow-up. A risk increase was observed with respect to melanomas and eye tumors in the entire cohort and lymphoma and tumors of the connective tissue in the subcohort of subjects living in villages with mainly arable land.
A number of studies carried out in different countries have shown that farmers have a low morbidity and mortality in comparison to those in other occupations. However, this has been questioned on the basis that some type of selective process may be operating, in that persons having health problems will avoid farming, or are forced to leave farming for other occupations. To determine the occurrence of a so-called 'healthy worker effect', this postal survey of 'elimination' from farming and farming-associated occupations has been carried out. A total of 1283 male farmers and 334 male farm workers born in 1935 and active in Sweden in 1970 were taken as the study group. As controls, a similar number of occupationally active men of the same age and living in the same municipalities were randomly chosen. The results showed that farmers changed occupation or retired early less often than those in other occupations did, whereas more farm workers changed occupation and retired than did other workers of the same age. Among the different reasons given for work change/retirement, low income/poor earning capacity was more common among the farmers and farm workers than among the controls. Illness was less common among farmers but tended to be more common among farm workers as cause of work change. Few farmers changed their occupation because they were offered other work, in comparison to those in other occupations. Allergic disease more often led to an occupation change among farmers, while they less often gave cardiac disease and locomotor problems as a reason for change of occupation, this was probably also true for the farm workers.(ABSTRACT TRUNCATED AT 250 WORDS)
PURPOSE: This analysis of the Agricultural Health Study cohort assesses the mortality experience of licensed pesticide applicators and their spouses. METHODS: This report is based on 52,393 private applicators (who are mostly farmers) and 32,345 spouses of farmers in Iowa and North Carolina. At enrollment, each pesticide applicator completed a 21-page enrollment questionnaire. Mortality assessment from enrollment (1994-1997) through 2000 provided an average follow-up of about 5.3 years, 447,154 person-years, and 2055 deaths. RESULTS: Compared with the general population in the two states, the cohort experienced a very low mortality rate. Standardized mortality ratios (SMRs) for total mortality, cardiovascular disease, diabetes, COPD, total cancer, and cancers of the esophagus, stomach, and lung were 0.6 or lower for both farmers and spouses. These deficits varied little by farm size, type of crops or livestock on the farm, years of handling pesticides, holding a non-farm job, or length of follow up. SMRs among ever smokers were not as low as among never smokers, but were still less than 1.0 for all smoking-related causes of death. No statistically significant excesses occurred, but slightly elevated SMRs, or those near 1.0, were noted for diseases that have been associated with farming in previous studies. CONCLUSIONS: Several factors may contribute to the low mortality observed in this population, including the healthy worker effect typically seen in cohorts of working populations (which may decline in future years), a short follow-up interval, and a healthier lifestyle manifested through lower cigarette use and an occupation that has traditionally required high levels of physical activity.
Musculoskeletal symptoms were reported by 215 fishermen followed at 6-month intervals over 18 months. Exposure information was collected through field observation and in-depth ethnographic interviews allowing potential ergonomic stressors to be identified and catalogued by task and stage of work. Symptoms causing work interference in the last 12 months were reported by 38.5% of the cohort at baseline. Low back symptoms were the most common cause of work impairment (17.7%), followed equally by pain in the hands or wrists and shoulders (7%). Symptoms in any body region were more likely to have been reported among individuals who did not fish full-time and those who worked other jobs part or all year had significantly lower symptom prevalence; both likely reflect a healthy worker effect. A number of ergonomic stressors were identified in all stages of fishing with exposure variability dictated by some unpredictable factors such as weather; but also by type of boat, gear, crew size, and level of experience. Reducing ergonomic exposures associated with work among these traditional workers is important, regardless of whether they directly cause or contribute to their musculoskeletal symptoms, or aggravate existing pathology.
PROBLEM: Low back pain (LBP) is one of the most prevalent work-related conditions affecting employed populations in developed countries, yet little is known about this condition among the world's largest, single-nation labor force: The People's Republic of China. METHOD: This is a cross-sectional study of the prevalence of low back pain (LBP) among garment workers, battery/kiln workers, and teachers in Shanghai, People's Republic of China. Data were collected by personal interview and physical examination at six work sites. The overall response rate was 78%. RESULTS: The overall (N=383) self-reported annual prevalence of LBP symptoms lasting 24 hours or more was 50%. Garment workers had a higher annual prevalence of LBP (74%) than teachers (40%), prevalence ratio (PR=1.9, 95% CI=1.4-2.4). DISCUSSION: The overall annual prevalence of self-reported LBP (50%) was higher than that reported among 50 other Chinese employed study populations (30%). Healthy worker effects may have limited the conclusions from this cross-sectional study. SUMMARY: These results suggest that LBP is a prevalent condition in Chinese workers and that more work should be done to estimate its impact on the Chinese workforce. The findings for garment workers were consistent with increased risk of LBP among persons doing work in fixed, sedentary postures.
OBJECTIVES: Epidemiologic studies have illustrated a possible association between occupational exposure to lead and cancer, specifically cancers of the kidney, lung, stomach, and nervous system. We performed a linkage between two New Jersey databases: the Adult Blood Lead Epidemiology and Surveillance System (ABLES) and the New Jersey State Cancer Registry (NJSCR) for 1985-2001 to ascertain the risk of cancer in lead-exposed workers and to evaluate the usefulness of this type of linkage. METHODS: A cohort of 3192 men from the ABLES database met the selection criteria before the linkage. AUTOMATCH was used to link the two databases. Person-time was stratified for each worker by five-year age group and calendar year. A standardized incidence ratios (SIR) analysis was performed. RESULTS: 83 cases of cancer were found among 3165 men after all exclusions were made. Workers were followed for an average of ten years and contributed 30,401 person-years. The SIR analysis showed a large overall deficit of cancer (SIR=0.51; 95% CI 0.41 to 0.62). Cancers of the stomach, breast, larynx, intrahepatic bile duct, and chronic myeloid leukemia were non-significantly elevated. Prostate cancer showed the only statistically significant result, a deficit with an SIR of 0.35 (95% CI 0.20 to 0.57). Deficits also occurred in cancers of the lung, kidney, and brain. CONCLUSIONS: The results do not indicate that occupational exposure to lead is associated with cancer. However, firm conclusions are not possible because of various study limitations, including small numbers, a large percentage of workers without age information, short follow-up time, and lack of vital status information. Cancer incidence in this cohort was expected to be low due to the Healthy Worker Effect and young age. Further follow-up of this cohort may be warranted since additional cancers may accrue as time from first exposure increases. Increased worker cohort information would also improve this type of study.
The analysis of an historical cohort study of mortality among individuals occupationally exposed to formaldehyde by Blair et al. (2) in 1986 failed to allow properly for the Healthy Worker Effect and to evaluate time integrated exposure and length of exposure simultaneously. In our reanalysis of the same data we find a risk for lung cancer, increasing with increasing cumulative exposure to formaldehyde.