Cardiovascular mortality and exposure to extremely low frequency magnetic fields: a cohort study of Swiss railway workers

<p>Abstract</p> <p>Background</p> <p>Exposure to intermittent magnetic fields of 16 Hz has been shown to reduce heart rate variability, and decreased heart rate variability predicts cardiovascular mortality. We examined mortality from cardiovascular causes in railway workers exposed to varying degrees to intermittent 16.7 Hz magnetic fields.</p> <p>Methods</p> <p>We studied a cohort of 20,141 Swiss railway employees between 1972 and 2002, including highly exposed train drivers (median lifetime exposure 120.5 μT-years), and less or little exposed shunting yard engineers (42.1 μT-years), train attendants (13.3 μT-years) and station masters (5.7 μT-years). During 464,129 person-years of follow up, 5,413 deaths were recorded and 3,594 deaths were attributed to cardio-vascular diseases. We analyzed data using Cox proportional hazards models.</p> <p>Results</p> <p>For all cardiovascular mortality the hazard ratio compared to station masters was 0.99 (95%CI: 0.91, 1.08) in train drivers, 1.13 (95%CI: 0.98, 1.30) in shunting yard engineers, and 1.09 (95%CI: 1.00, 1.19) in train attendants.Corresponding hazard ratios for arrhythmia related deaths were 1.04 (95%CI: 0.68, 1.59), 0.58 (95%CI: 0.24, 1.37) and 1.30 (95%CI: 0.87, 1.93) and for acute myocardial infarction 1.00 (95%CI: 0.73, 1.36), 1.56 (95%CI: 1.04, 2.32), and 1.14 (95%CI: 0.85, 1.53). The hazard ratio for arrhythmia related deaths per 100 μT-years of cumulative exposure was 0.94 (95%CI: 0.71, 1.24) and 0.91 (95%CI: 0.75, 1.11) for acute myocardial infarction.</p> <p>Conclusion</p> <p>This study provides evidence against an association between long-term occupational exposure to intermittent 16.7 Hz magnetic fields and cardiovascular mortality.</p

Demographic and occupational predictors of early response to a mailed invitation to enroll in a longitudinal health study

BACKGROUND: Often in survey research, subsets of the population invited to complete the survey do not respond in a timely manner and valuable resources are expended in recontact efforts. Various methods of improving response have been offered, such as reducing questionnaire length, offering incentives, and utilizing reminders; however, these methods can be costly. Utilizing characteristics of early responders (refusal or consent) in enrollment and recontact efforts may be a unique and cost-effective approach for improving the quality of epidemiologic research. METHODS: To better understand early responders of any kind, we compared the characteristics of individuals who explicitly refused, consented, or did not respond within 2 months from the start of enrollment into a large cohort study of US military personnel. A multivariate polychotomous logistic regression model was used to estimate the effect of each covariate on the odds of early refusal and on the odds of early consent versus late/non-response, while simultaneously adjusting for all other variables in the model. RESULTS: From regression analyses, we found many similarities between early refusers and early consenters. Factors associated with both early refusal and early consent included older age, higher education, White race/ethnicity, Reserve/Guard affiliation, and certain information technology and support occupations. CONCLUSION: These data suggest that early refusers may differ from late/non-responders, and that certain characteristics are associated with both early refusal and early consent to participate. Structured recruitment efforts that utilize these differences may achieve early response, thereby reducing mail costs and the use of valuable resources in subsequent contact efforts

[An Introduction To the Statistical Design of Phase-iii Cancer Clinical-trials]

A phase III clinical trial is a comparative study in which one assesses the relative efficacy of a treatment or treatments. It generally has one of the following objectives: 1. To determine the effectiveness of a new treatment relative to the natural history of the disease, for example when comparing a new treatment to not treatment or to placebo in an adjuvant setting. 2. To determine if a new treatment is more effective than the best current standard therapy (at the risk of increasing the toxicity). 3. To determine if a neu treatment is as effective as the best current standard therapy but is associated with less severe toxicity or a better quality of life (equivalence trial). Clinical trials must be properly designed in order to asnwer such questions with a high degree of certainty. The purpose of this paper is to present several concepts which must be taken into account during the process of designing a clinical trial

Reproducibility of microscopic and cultural data in repeated subgingival plaque samples.

In association studies, micro-organisms can only be recognized as suspects for playing a major rôle in the development of a pathological environment, if their destructive action goes along with a marked proportional increase of their numbers or if their first detection can be related to the clinical onset of the disease. Limitations in the reproducibility of repeated samples have to be taken into account, when changes of the microbial composition of subgingival environments are to be studied, and when local clinical changes are to be related to shifts in the composition of the pertaining microbiological compartment. To study reproducibility, a total of 109 sites was sampled repeatedly with sterile paperpoints at an interval of 7 to 10 days in 24 patients suffering from periodontal disease and 12 edentulous patients wearing successful and failing osseointegrated titanium implants. Using continuous anaerobic techniques, the samples were cultured on nonselective and selective media and were studied by darkfield microscopy. Both the intertest-agreements of frequencies of detection (kappa-statistics) as well as the discrepancies of proportions of bacterial groups and selected bacterial species were determined. The standard deviation of proportional differences between first and second samples ranged between 6.4% (fusiform organisms) and 17.2% (coccoid cells) for darkfield parameters, between 4.3% (B. melaninogenicus on ETSA/Kana.) and 14.0% (B. gingivalis on ETSA/Kana.) for selected bacterial species and between 6.9% (gram-negative anaerobic cocci) and 24.0% (gram-positive facultative cocci) for bacterial groups classified according to gram stain characteristics and atmospheric growth conditions.(ABSTRACT TRUNCATED AT 250 WORDS)link_to_subscribed_fulltex

Periodontal conditions in a randomly selected population in Switzerland.

The aim of the present study was to evaluate the periodontal conditions of a randomly selected population in the Canton of Berne, Switzerland. From a total of 350 selected persons, 206 (59%) attended the examinations. The Plaque Index (PlI), Gingival Index (GI) and Retention Index (RI), the width of the keratinized gingiva, pocket probing depth (PD) and loss of probing attachment (LA) were recorded on four surfaces per tooth in the entire dentition of the subjects. The statistical analyses were performed using the Statistical Analysis System (SAS). A total of 4253 teeth were scored. On average the patients had 20.7 teeth. The mean PlI of this population was 1.16, the mean GI was 1.34 and the mean RI was 0.81. All three indices were higher in older age groups. 72% of all measurements for pocket probing depths were less than or equal to 3 mm, 26% were between 4 and 6 mm, and only 2% were more than 6 mm. 76% of all sites had lost less than or equal to 3 mm of probing attachment, 21% of the sites had lost between 4 and 6 mm and only 3% had lost more than 6 mm. There were no statistically significant differences either between females and males or between the rural and the urban populations. These results indicate that only a relatively small percentage of the sample representative for the respective area in Switzerland suffered from advanced periodontitis, while the great majority may be treated by rather conservative approaches to periodontal therapy.link_to_subscribed_fulltex

Comparison of clinical periodontal parameters with the Community Periodontal Index for Treatment Needs (CPITN) data.

The purpose of this analysis was to assess the ability of the CPITN system to rate severity and prevalence of periodontal diseases in a population, in comparison with full mouth scorings using conventional clinical parameters (Plaque Index, Gingival Index, Retention Index, Pocket Probing Depth and Loss of Attachment). These parameters were collected in a randomly selected sample in Switzerland. The data were then transformed to fit the definitions of the CPITN. Furthermore, a comparison of the data set from Switzerland with data obtained from the Oral Global Data Bank of the WHO was made. By conversion of the Swiss data into the CPITN format, many details were lost, which were considered to be relevant to assess severity, prevalence and localization of periodontal diseases within a population. In addition, the transformed data generally overestimated the prevalence of periodontal destruction when compared with data from surveys in other industrialized countries in which the CPITN was used to evaluate the periodontal status. The comparison of the data before transformation into the CPITN, however, corroborated results from epidemiological studies in which conventional periodontal index systems were used. This indicates that data obtained to determine defined treatment needs (CPITN) may be of questionable value for the assessment of the true prevalence and severity of periodontal disease in a population.link_to_subscribed_fulltex

The periodontal status of the population of 12 cantons in Switzerland | Parodontaler Zustand der Bevölkerung in zwölf Kantonen der Schweiz.

An epidemiological survey in 12 cantons of Switzerland yielded a high percentage of all the sites examined with signs of gingivitis. Nevertheless, only 4% of all the sites showed periodontal breakdown of 7 mm or more; however, those sites were distributed in larger proportions of the population sample. Further frequency analysis revealed that more than 75% of the persons examined yielded no or only few sites with periodontal breakdown. The results of this study indicate that despite the high percentage of inflamed gingival units in the population, periodontal breakdown is less frequent than commonly estimated.link_to_subscribed_fulltex