It is now twenty years since Wertheimer and Leeper (1979) published the first study suggesting an association between residential exposure to extremely low frequency magnetic fields (EMF) and childhood cancer. Ever since, this has been a controversial issue with the findings from several, but not all, subsequent epidemiological studies being consistent with an association, particularly with respect to residential exposure and childhood leukaemia (Portier and Wolfe, 1998). However, many of the reports have been based on small numbers of exposed cases, and despite intense experimental research no known biophysical mechanism to explain an effect has been established.We conducted a pooled analysis based on primary data from nine studies on EMF and childhood leukaemia, addressing three specific questions:1. Do the combined results of these studies indicate that there is an association between EMF exposure and childhood leukaemia risk, which is larger than one would expect from random variability?2. Does adjustment for confounding from socioeconomic class, mobility, level of urbanization, detached/not detached dwelling, and level of traffic exhaust change the results? 3. Do the combined data support the existence of the so-called wire code paradox, that is, a stronger association between proxy measures of EMF and cancer than between direct measurements and cancer? METHODSThe original plan for this project was to include all European studies that addressed the question of an association between EMF and childhood leukaemia and were based on either 24 or 48 hour magnetic field measurements or calculated fields. At the time five such studies were reported (Feychting and Ahlbom, 1993; Olsen et al, 1993;Verkasalo et al, 1993;Tynes and Haldorsen, 1997;Michaelis et al, 1998). In addition, a nationwide childhood cancer study was in progress and near completion in the UK (UKCCS, 1999). Since we were not aware of any other European study to be published in the near future, the inclusion of the UK study would give us a complete set of European studies. We felt that if we could also incorporate new studies from non-European countries this pooled analysis would be up to date and presumably stay current for several years. We were aware of three more studies in other parts of the world with compatible information that were all nearly A pooled analysis of magnetic fields and childhood leukaemia Summary Previous studies have suggested an association between exposure to 50-60 Hz magnetic fields (EMF) and childhood leukaemia. We conducted a pooled analysis based on individual records from nine studies, including the most recent ones. Studies with 24/48-hour magnetic field measurements or calculated magnetic fields were included. We specified which data analyses we planned to do and how to do them before we commenced the work. The use of individual records allowed us to use the same exposure definitions, and the large numbers of subjects enabled more precise estimation of risks at high exposure levels. For the 3203 children with leukae...

For rehabilitation professionals engaged in the treatment of osteoarthritis (OA), it is standard practice to perform objective assessments of physical function (using both physical performance and self-report measures) to obtain a picture of patient status. These assessments also serve as a baseline value for estimating changes (treatment effects) over time. While reliability and validity of some commonly used physical performance measures have been investigated in an OA population, most require further research regarding clinical utility and responsiveness. 14 Physical performance measures have often been criticized, as detailed testing of their measurement properties has not been extensively reported. 14,22,33 Measures of responsiveness have commonly been reported as statistically significant change scores, which are useful in establishing the threshold of change needed beyond measurement error. 10 Investigation of minimal clinically important differences (MCIDs) of physical performance measures is warranted, as these have become commonly used outcome measures in the treatment of OA. 8,12,17,[35][36][37] At present, the responsiveness (in terms of MCID) of the timed up-and-go (TUG) test, 40-meter self-paced walk test (40-m SPWT), 30-second chair stand (30 CST), and 20-cm step test has not been investigated in T T STUDY DESIGN: Prospective cohort study. T T OBJECTIVES:To establish the major clinically important improvement (MCII) of the timed upand-go test (TUG), 40-meter self-paced walk test (40-m SPWT), 30-second chair stand (30 CST), and a 20-cm step test in patients with hip osteoarthritis (OA) undergoing physiotherapy treatment. As a secondary aim, a comparison of methods was employed to evaluate the effect of method on the reported MCII. T T BACKGROUND: Minimal clinically importantdifference scores are commonly used by rehabilitation professionals to determine patient response following treatment. A gold standard for calculating MCII has yet to be determined, which has resulted in problems of interpretation due to varied results. T T METHODS:As part of a randomized controlled trial, 65 patients were randomized into a physiotherapy treatment group for hip OA, in which they completed 4 physical performance measures at baseline and 9 weeks. Upon completion of physiotherapy, patients assessed their response to treatment on a 15-point global rating of change scale (GRCS). MCII was estimated using 3 variations of an anchor-based method, based on the patient's opinion. T T RESULTS:A comparison of 3 methods resulted in the following change scores being best associated with our definition of MCII: a reduction equal to or greater than 0.8, 1.4, and 1.2 seconds for the TUG; an increase equal to or greater than 0.2, 0.3, and 0.2 m/s for the 40-m SPWT; an increase equal to or greater than 2.0, 2.6, and 2.1 repetitions for the 30 CST; an increase equal to or greater than 5.0, 12.8, and 16.4 steps for the 20-cm step test. T T CONCLUSION:The variation in methods provided very different results. This illustrates the impor...

The associations between ALL and parental ages did not disappear when children with Down syndrome were excluded, suggesting an additional explanation beyond known links. The strong ALL association with parity may be because of an unknown environmental risk factor.