Kenneth A. Mundt

Confidence intervals for measures of interaction.

&NA; Interaction, defined as departure of disease rates from an additive model, can be measured by the relative excess risk due to interaction, or the attributable proportion due to interaction. Point estimates can be obtained using multiple logistic regression. Using simulated case‐control data, we compare several confidence interval estimation techniques for these measures. These include a symmetrical interval based on the delta method estimate of the variance, and three types of bootstrap confidence intervals. One such bootstrap method has coverage closest to the nominal level and is the most evenly balanced with respect to the direction in which intervals miss the true value. The estimation methods are applied to data from an actual case‐control study, and the results are interpreted in light of the simulation study.

Video display terminal workstation improvement program: I. Baseline associations between musculoskeletal discomfort and ergonomic features of workstations.

Associations between selected sites of musculoskeletal discomfort and ergonomic characteristics of the video display terminal (VDT) workstation were assessed in analyses controlling for demographic, psychosocial stress, and VDT use factors in 273 VDT users from a large administrative department. Significant associations with wrist/hand discomfort were seen for female gender; working 7+ hours at a VDT; low job satisfaction; poor keyboard position; use of new, adjustable furniture; and layout of the workstation. Significantly increased odds ratios for neck/shoulder discomfort were observed for 7+ hours at a VDT, less than complete job control, older age (40 to 49 years), and never/infrequent breaks. Lower back discomfort was related marginally to working 7+ hours at a VDT. These results demonstrate that some characteristics of VDT workstations, after accounting for psychosocial stress, can be correlated with musculoskeletal discomfort.

Measuring Ankle Systolic Blood Pressure: Validation of the Dinamap 1846 SX

Clinical and epidemiologic situations requiring repeated measurements of blood pressure in the lower extremity are increasingly incorporating automated measurement devices; however, no device has been validated adequately for ankle blood pressure. This study evaluates the Dinamap 1846 SX against Dop pler ultrasound in determining ankle systolic blood pressure (SBP) and com pares a parallel with contour wrapping technique for applying the blood pres sure cuff. Ankle SBP was measured on 71 adult volunteers by both devices simultaneously, for each cuff wrap. Averages of three readings were compared to evaluate Dinamap versus Doppler SBP estimates and to assess any cuff wrap effect. Multiple linear regression was used to assess potential effect modifiers. Instrument differences (Dinamap minus Doppler) for the parallel wrap (95% confidence intervals in parenthesis) were —1.5 mmHg (-3.1, 0.0) and — 3.9 mmHg (-5.6, -2.2) for the contour wrap. Wrap effect differences (contour minus parallel) for the Doppler were -4.9 mmHg (-6.3, -3.5) and -7.2 mmHg ( — 8.7, — 5.8) for the Dinamap. Degree of ankle taper was a strong modi fier of cuff effect for the Dinamap but not for the Doppler: adjusted cuff effect with the Dinamap ranged from — 3 to —10 mmHg. Measurement precision (within-person reproducibility, measured by within-person standard deviation [σ 2] and reliability coefficient [R]) was higher for the Dinamap than the Doppler technique, lowest for the parallel wrap and Doppler configuration (σ2 = 5.4 mmHg, R = 0.88) and greatest for the contour wrap and Dinamap (σ2 = 4.0 mmHg, R = 0.94). In conclusion, cuff-wrapping technique can generate SBP differences of greater magnitude than instrument differences. Conditional on the use of the contour wrap, and by virtue of its high repeatability and ease of operation, the Dinamap is a useful tool for epidemiologic study and the clinical assessment of peripheral arterial disease.

Historical cohort study of 10 109 men in the North American vinyl chloride industry, 1942–72: update of cancer mortality to 31 December 1995

OBJECTIVES To update and assess mortality from neoplasms to 31 December 1995 among 10 109 men employed in a job exposed to vinyl chloride for at least 1 year between 1942 and 1972 at any of 37 North American factories. Previous analyses indicated associations between employment in vinyl production and increased mortality risk from cancers of the liver and biliary tract, due to increased mortality from angiosarcoma of the liver, and brain cancer. METHODS Standardised mortality ratio (SMR) analyses, overall and stratified by several work related variables, were conducted with United States and state reference rates. Coxs proportional hazards models and stratified log rank tests were used to further assess occupational factors. RESULTS 895 of 3191 deaths (28%) were from malignant neoplasms, 505 since the previous update to the end of 1982. Mortality from all causes showed a deficit (SMR 83, 95% confidence interval (95% CI) 80 to 86), whereas mortality from all cancers combined was similar to state referent rates. Mortality from cancers of the liver and biliary tract was clearly increased (SMR 359, 95% CI 284 to 446). Modest excesses of brain cancer (SMR 142, 95% CI 100 to 197) and cancer of connective and soft tissue (SMR 270, 95% CI 139 to 472) were found. Stratified SMR and Coxs proportional hazard analyses supported associations with age at first exposure, duration of exposure, and year of first exposure for cancers of the liver and soft tissues, but not the brain. CONCLUSIONS Excess mortality risk from cancer of the liver and biliary tract, largely due to angiosarcoma, continues. Risk of mortality from brain cancer has attenuated, but its relation with exposure to vinyl chloride remains unclear. A potentially work related excess of deaths from cancer of connective and soft tissue was found for the first time, but was based on few cancers of assorted histology.

Lung cancer mortality among chromate production workers

Aims: To assess mortality in 1997 among 493 former workers of a US chromate production plant employed for at least one year between 1940 and 1972. Methods: Cohort members were followed for mortality to 31 December 1997. Standardised mortality ratios (SMRs) were calculated for selected cause specific categories of death including lung cancer. Lung cancer mortality was investigated further by calculation of SMRs stratified by year of hire, duration of employment, time since hire, and categories of cumulative exposure to Cr(VI). Results: Including 51 deaths due to lung cancer, 303 deaths occurred. SMRs were significantly increased for all causes combined (SMR = 129), all cancers combined (SMR = 155), and lung cancer (SMR = 241). A trend test showed a strong relation between lung cancer mortality and cumulative hexavalent exposure. Lung cancer mortality was increased for the highest cumulative exposure categories (⩾1.05 to <2.70 mg/m3-years, SMR = 365; ⩾2.70 to 23 mg/m3-years, SMR = 463), but not for the first three exposure groups. Significantly increased SMRs were also found for year of hire before 1960, 20 or more years of exposed employment, and latency of 20 or more years. Conclusions: The finding of an increased risk of lung cancer mortality associated with Cr(VI) exposure is consistent with previous reports. Stratified analysis of lung cancer mortality by cumulative exposure suggests a possible threshold effect, as risk is significantly increased only at exposure levels over 1.05 mg/m3-years. Though a threshold is consistent with published toxicological evidence, this finding must be interpreted cautiously because the data are also consistent with a linear dose response.

Risk factors for psychological stress among international business travellers.

OBJECTIVES: This study investigated sources of self reported psychological stress among international business travellers at the World Bank, following up on a previous study showing that travellers submitted more insurance claims for psychological disorders. Hypotheses were that work, personal, family, and health concerns, as well as time zone travel, contribute to travel stress. METHODS: A travel survey was developed from focus groups and consisted of questions about these potential sources of travel stress. Surveys were sent to a random sample of staff, stratified by number of travel missions, age range, and sex. Canonical correlation analyses estimated the association between key survey items on sources of stress and two measures of travel stress. RESULTS: 498 staff completed the survey. More than a third reported high to very high travel stress. Correlations between predictors and travel stress showed that social and emotional concerns (such as impact of travel on family and sense of isolation) contributed the most to such stress, followed by health concerns, and workload upon return from travel. Surprisingly, time zone travel did not contribute to the self reported stress of these travellers. There were few modifiers of stress, although respondents suggested that a day of rest after travel and reduced workloads would help. CONCLUSIONS: The current study confirms clinical impressions about several correlates of travel stress. Similar research with travellers in other organisations could help to determine whether the findings from this study are valid and what measures can be taken to reduce the psychological health risks to travellers.

Cancer mortality among workers in the German rubber industry: 1981-91.

OBJECTIVES: To determine the cancer specific mortality of active and retired workers of the German rubber industry with emphasis on cancer sites which have been associated with the rubber industry in previous studies. METHODS: A cohort of 11,663 German men was followed up for mortality from 1 January 1981 to 31 December 1991. Cohort members were active (n = 7536) or retired (n = 4127) at the beginning of the study, and had been employed for at least one year in one of five study plants producing types or general rubber goods. Vital status was ascertained for 99.7% of the cohort members, and cause of death found for 96.8% of the 2719 decedents. Age and calendar year adjusted standardised mortality ratios (SMR) and 95% confidence intervals (95% CI) were calculated overall from national reference rates and stratified by year of hire and by years since hire. RESULTS: Mortalities from all causes (SMR 108; 95% CI 104-112) and all cancers (SMR 111; 95% CI 103-119) were significantly increased in the study cohort. Significant excesses in the mortalities from lung cancer (SMR 130; 95% CI 115-147) and pleural cancer (SMR 401; 95% CI 234-642) were identified. SMRs higher than 100 were found for cancers of the pharynx (SMR 144; 95% CI 76-246), oesophagus (SMR 120; 95% CI 74-183), stomach (SMR 110; 95% CI 86-139), rectum (SMR 123; 95% CI 86-170), larynx (SMR 129; 95% CI 69-221), prostate (SMR 108; 95% CI 84-136), and bladder (SMR 124; 95% CI 86-172), as well as for leukaemia (SMR 148; 95% CI 99-213). Mortalities from liver cancer, brain cancer, and lymphoma were lower than expected. CONCLUSIONS: Mortalities from cancer of several sites previously associated with the rubber industry were also increased among workers of the German rubber industry. Results of the stratified analyses are consistent with a role of occupational exposure in the aetiology of some of these cancers.

Parental occupational exposures and risk of neuroblastoma: a case–control study (United States)

AbstractBackground: A case–control study was conducted with 183 histologically confirmed neuroblastoma cases aged 0–14 years diagnosed among residents of New York State, excluding New York City, between 1976 and 1987. Three hundred seventy-two controls were selected from the New York State live birth certificate registry and were matched to cases on year of birth. Methods: Parental occupational exposures at the time of each childs birth were obtained from maternal telephone interviews, successfully completed for 85% of cases and 87% of controls. Results: Odds ratios were significantly elevated for maternal occupation in the service (OR = 2.0, 95% CI = 1.0–4.1) and retail (OR = 2.0, 95% CI = 1.1–3.7) industries and paternal occupation in materials handling (OR = 3.8, 95% CI = 1.1–14.6). Odds ratios were also significantly elevated for maternal report of occupational exposure to acetone (OR = 3.1, 95% CI = 1.7–5.6), insecticides (OR = 2.3, 95% CI = 1.4–3.7), lead (OR = 4.7, 95% CI = 1.3–18.2) and petroleum (OR = 3.0, 95% CI = 1.5–6.1) and paternal exposure to creosote (OR = 2.1, 95% CI = 1.1–4.3), dioxin (OR = 6.9, 95% CI = 1.3–68.4), lead (OR = 2.4, 95% CI = 1.2–4.8), and petroleum (OR = 1.8, 95% CI = 1.1–2.8). Conclusions: Due to the uncertainty of the biologic plausibility of these associations and the possibility of alternative explanations, these results should be interpreted cautiously.

Lung cancer mortality in the german chromate industry, 1958 to 1998

Objectives: We conducted a mortality study of two German chromate production facilities and evaluated possible dose-response relationships between hexavalent chromium exposure and lung cancer. Methods: Mortality was followed-up through 1998 and limited to those employed since each plant converted to a no-lime production process. More than 12,000 urinalysis results of chromium levels were available, as was smoking information. Results: All-cause mortality indicated a healthy worker effect (standardized mortality ratio [SMR] = 0.80, 95% confidence interval [CI] = 0.67–0.96); however, lung cancers appeared to be increased (SMR = 1.48, 95% CI = 0.93–2.25). No clear dose-response was found in stratified analyses by duration of employment and time since hire. On the basis of urinary chromium data, lung cancer risk was elevated only in the highest exposure group (SMR = 2.09, 95% CI = 1.08–3.65). Conclusions: These data suggest a possible threshold effect of occupational hexavalent chromium exposure on lung cancer.

Video display terminal workstation improvement program: II. Ergonomic intervention and reduction of musculoskeletal discomfort.

The effects of an ergonomic intervention on musculoskeletal discomfort in 118 video display terminal (VDT) users were assessed 1 year after intervention. The intervention consisted of recommended changes to workstations, which were based on the evaluation of 15 ergonomic characteristics. Compliance with the intervention was at least 75% for most workstation characteristics. Reduction in discomfort was substantial and was highest for the wrist/hand (57%), lower back (43%), and neck/shoulder (41%) severity of discomfort outcomes. Neither compliance with intervention on individual workstation characteristics nor summary intervention scores were associated with reduction in discomfort. Our results demonstrate that although reduction of musculoskeletal discomfort may be observed in the context of an intervention study, it may be difficult to link these benefits to specific interventions.