Neurobehavioral effects among subjects exposed to high static and gradient magnetic fields from a 1.5 Tesla magnetic resonance imaging system--a case-crossover pilot study.

The interactive use of magnetic resonance imaging (MRI) techniques is increasing in operating theaters. A study was performed on 17 male company volunteers to assess the neurobehavioral effects of exposure to magnetic fields from a 1.5 Tesla MRI system. The subjects' neurobehavioral performances on a neurobehavioral test battery were compared in four 1-hr sessions with and without exposure to magnetic fields, and with and without additional movements. Adverse effects were found for hand coordination (-4%, P < 0.05; Pursuit Aiming II) and near visual contrast sensitivity (-16% and -15%, P < 0.10; Vistech 6000). The results from the remaining tests were inconclusive due to a strong learning effect. No additional effect from gradient fields was detected. The results indicate that working near a 1.5 Tesla MRI system may lead to neurobehavioral effects. Further research is recommended, especially in members of operating teams using interactive MRI systems.     

Predictive value of repeated systolic blood pressure measurements for stroke risk. The Zutphen Study.

BACKGROUND AND PURPOSE: The strength of the association between blood pressure and stroke incidence is dependent on the number of blood pressure measurements. Different summary variables of repeated blood pressure measurements taken during 10 years were evaluated in relation to the long-term risk of stroke in the Zutphen Study. METHODS: During the period 1960-1970 repeated blood pressure measures were taken yearly in 603 men aged 50-69 years in 1970 in the town of Zutphen, The Netherlands. The individual average systolic blood pressure between 1960 and 1970, the predicted systolic blood pressure for 1970 (based on regression of blood pressure readings on time), and the single observed systolic blood pressure in 1970 were used as systolic blood pressure estimates. Their strength in predicting the 15-year stroke incidence was assessed using Cox proportional hazards models. Adjustment was made for the confounding effects of age, cigarette smoking, and serum total cholesterol. RESULTS: The average systolic blood pressure between 1960 and 1970 was the strongest predictor of 15-year stroke incidence. The strength of the association was underestimated by 55% when a casual systolic blood pressure measurement was used instead of 11 yearly measurements. CONCLUSIONS: It can be concluded that a casual blood pressure measurement leads to a substantial underestimation of the long-term stroke risk of an individual.     

Inter-cohort differences in coronary heart disease mortality in the 25-year follow-up of the seven countries study

Sixteen cohorts of men aged 40–59 years at entry were examined with the measurement of some risk factors and then followed-up for mortality and causes of death for 25 years. These cohorts were located in the USA (1 cohort), Finland (2), the Netherlands (1), Italy (3), the former Yugoslavia (5), Greece (2), and Japan (2), and included a total of 12,763 subjects.Large differences in age-adjusted coronary heart disease (CHD) death rates were found, with extremes of 45 per 1000 in 25 years in Tanushimaru, Japan, to 288 per 1000 in 25 years in East Finland. In general, higher rates were found in the US and Northern European cohorts as compared to the Southern European and Japanese cohorts. However, during the last 10 years of follow-up large increases of CHD death rates were found in some Yugoslavian areas. Out of 5 measured entry characteristics treated as age-adjusted levels (serum cholesterol, systolic blood pressure, cigarette smoking, body mass index and physical activity at work), only serum cholesterol was significant in explaining cohort differences in CHD death rates.Over 50% of the variance in CHD death rates in 25 years was accounted for by the difference in mean serum cholesterol. This association tended to decline with increasing length of follow-up, but this was due to the great changes in mean serum cholesterol in the two Jugoslavian cohorts of Velika Krsna and Zrenjanin. When these two cohorts were excluded the association increased with time.Changes in mean serum cholesterol between year 0 and 10 helped in explaining differences in CHD death rates from year 10 onward.It can be concluded that this study suggests that mean serum cholesterol is the major risk factor in explaining cross-cultural differences in CHD.     

Urothelial cell DNA adducts in rubber workers

Workers employed in the rubber industry appear to have a significant excess cancer risk in a variety of sites, including cancer of the urinary bladder. In this cross-sectional study, we investigated the occurrence of DNA adducts in exfoliated bladder cells of currently exposed, nonsmoking rubber workers (n = 52) and their relationship with occupational exposure estimates and acetylation phenotype (NAT2). Four DNA adducts were identified, with the proportion of positive samples (e.g., DNA samples with quantifiable levels of a specific DNA adduct) ranging from 3.8 to 79%. The highest proportion of positive samples and the highest relative adduct labeling levels were in workers involved in the production functions "mixing" and "curing," areas with potential for substantial exposure to a wide range of chemical compounds used in rubber manufacturing (P < 0.05 for adducts 2 and/or 3, compared to all other departments). No statistically significant relationships were found between identified DNA adducts and urinary mutagenicity or personal inhalable and dermal exposure estimates. Interestingly, subjects with a fast NAT2 acetylation phenotype tended to have higher levels of DNA adducts. This study suggests that rubber workers engaged in mixing and curing may be exposed to compounds that can form DNA adducts in urothelial cells. Larger studies among rubber workers should be conducted to study in more detail the potential carcinogenicity of exposures encountered in these work areas.     

"John Henryism" and blood pressure in a Dutch population

In a stratified, random sample of 100 men and 100 women, aged 20-59 years, residing in Zutphen, the Netherlands, the hypothesis was tested that high scores on "John Henryism," a strong behavioral predisposition to cope actively with psychosocial environmental stressors, would be associated with higher blood pressure, especially among persons of lower education. In univariate analyses higher scores on John Henryism were strongly associated with higher blood pressures in men. Among women there was only an association of John Henryism and systolic blood pressure, but this association was no longer statistically significant after adjustment for potential confounders such as age, alcohol consumption, physical activity, Quetelet Index, and education. Among men, however, the association between John Henryism and systolic blood pressure remained statistically significant after adjustment for potential confounders. The association between John Henryism and blood pressure was more pronounced for men of low educational background.     

Dietary flavonoids and cancer risk in the Zutphen Elderly Study

Flavonoids are polyphenolic antioxidants naturally present in vegetable foods. Some flavonoids, such as quercetin, inhibit carcinogenesis in rodents, but their effect in humans is unknown. We measured the flavonoids quercetin, kaempferol, myricetin, apigenin, and luteolin in foods and assessed flavonoid intake in 1985 by dietary history in 738 men aged 65-84 years without a history of cancer, who were then followed for five years. Mean flavonoid intake was 25.9 mg/day. The major sources of flavonoid intake were tea at 61% and vegetables and fruits (mainly onions, kale, endive, and apples) at 38%. Between 1985 and 1990, 75 men developed cancer (all sites) and 34 men died from cancer. Flavonoid intake in 1985 was not associated with incidence of all-cause cancer (p for trend = 0.54) or with mortality from all-cause cancer (p for trend = 0.51). Flavonoid intake was also not associated with risk of cancers of the alimentary and respiratory tract (p for trend = 0.92). Adjustment for age, body mass index, smoking, physical activity, and vitamin C, vitamin E, beta-carotene, and dietary fiber intake did not change the relative risks. A high intake of flavonoids from vegetables and fruits only was inversely associated with risk of cancer of the alimentary and respiratory tract (relative risk of highest vs. lowest tertile = 0.51, 95% confidence interval 0.25-1.05); these results suggest the presence of other nonvitamin components with anticarcinogenic potential in these foods. We conclude that intake of flavonoids, mainly from tea, apples, and onions, does not predict a reduced risk of all-cause cancer or of cancer of the alimentary and respiratory tract in elderly men. The effect of flavonoids on risk of cancer at specific sites needs further investigation in prospective cohort studies.     

Within-day variability of magnetic fields among electric utility workers: consequences for measurement strategies

Occupational exposure to 50-Hz magnetic fields was surveyed among electric utility workers to investigate (1) components of exposure variability, (2) patterns of autocorrelation between short-term measurements, and (3) imprecision and misclassification due to short-term measurements. Spot measurements every 10 seconds during 81 working days were analyzed for 42 electric utility workers from 10 occupational subgroups and during 8 working days for 4 office workers from the same company. For the 8-hour time-weighted average (TWA) magnetic fields, the variability was partitioned into its components: within workers, between workers, and between groups. For spot measurements of magnetic fields, the within-day variance component also was examined. Autocorrelation functions were determined and numbers of short-term measurements necessary for reliable estimates of 8-hour TWA magnetic fields were assessed. Spot measurements of magnetic fields, as well as 8-hour TWA magnetic fields, were approximately log normally distributed among workers. The mean exposure to magnetic fields was 0.47 microT (n = 81 days) in electric utility workers and 0.12 microT (n = 8 days) in office workers. A large fraction, 76% of the spot measurements total variance, could be attributed to variability within days. For the 8-hour TWA magnetic fields, between-group variability was small and of the same magnitude as between-worker variability. Significant autocorrelations between short-term averages of 7.5, 15, and 30 minutes were present, when taken within periods of 30 minutes. One-hour averages showed no autocorrelation. Simulations showed that, due to high within-day variability and autocorrelation, a limited number of short-term measurements of magnetic fields in electric utility workers are likely to result in imprecise estimates of 8-hour TWA magnetic fields. Measurement strategies relying on short-term (spot) measurements are therefore likely to result in misclassification of exposure and consequently absent or spurious exposure-response relations.     

Plasma concentrations of the antioxidants beta-carotene and alpha-tocopherol in relation to lung function

OBJECTIVE: To study the association between plasma antioxidants (beta-carotene and alpha-tocopherol) and lung function in Dutch adults aged 20-59 y. DESIGN: Cross-sectional. SETTING: Population-based study. Subjects: A random sample (n=367) was drawn from all participants (men and women) aged 20-59 y with reproducible lung function measurements in 1995. INTERVENTION: Completion of general questionnaire and physical examination. MAIN OUTCOME MEASUREMENTS: Forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and plasma levels of beta-carotene and alpha-tocopherol. RESULTS: Subjects with a high plasma beta-carotene level (90th percentile, that is 0.57 micromol/L) tended to have a higher FEV1 (73 ml, s.e.m. 60 ml; P=0.22) and a higher FVC (147 ml, s.e.m. 76 ml; P=0.05) than subjects with a low plasma beta-carotene level (10th percentile, that is 0.11 micromol/L) after adjustment for age, height, gender, smoking status, pack-years of smoking and alcohol consumption. There was no difference in lung function between subjects with high and low plasma alpha-tocopherol concentrations. CONCLUSIONS: The results suggest that subjects with a high plasma beta-carotene tended to have a higher FVC than subjects with a low plasma beta-carotene concentration which was borderline statistically significant. The difference for FEV1 between high and low levels of plasma beta-carotene tended to be in the same positive direction as that of FVC but did not reach the pre-set statistical significance level. There is no relation between plasma alpha-tocopherol and lung function. SPONSORSHIP: Ministry of Public Health, Welfare and Sports of the Netherlands and the National Institute of Public Health and the Environment.     

Use of qualitative and quantitative fluorescence techniques to assess dermal exposure

Fluorescent tracers provide a way of simultaneously assessing the mass of a contaminant hazardous substance on the surface of the skin of a worker and the area of skin exposed. These parameters, along with the duration of exposure and the estimated contaminant concentration in the skin contamination layer, can be used to calculate the likely uptake through the skin. Repeated assessment of the mass of tracer on a surface within a room or on the surface of the skin can also allow the net transfer of contaminant to that compartment to be estimated. Qualitative evaluation of transfer processes using fluorescent tracers can help identify important secondary sources of exposure.     

Leisure time physical activity and health-related quality of life: Cross-sectional and longitudinal associations

Studies that relate change in physical activity to change in health-related quality of life in the general population are needed to confirm associations suggested by cross-sectional studies. In the present study, cross-sectional as well as longitudinal associations between leisure time physical activity and health-related quality of life were studied in an apparently healthy population. The present study showed cross-sectional associations between at least moderately intense leisure time physical activity and general health perceptions, vitality, physical functioning and role limitations due to physical health problems. No associations were present for total leisure time physical activity. Change in leisure time physical activity was associated with change in social functioning in men as well as in women, irrespective of the intensity of physical activity. Only in men, change in total leisure time physical activity was associated with change in vitality and general mental health. In our study, cross-sectional associations were not confirmed by longitudinal analyses. Cross-sectional associations were mainly found for physical components of health-related quality of life, whereas longitudinal associations were predominantly observed for mental components of health-related quality of life. Confirmation of our results by those of other studies is needed in order to quantify health promotion messages.