Personal Continuity and Appropriate Prescribing in Primary Care.

PURPOSE: Personal continuity between patient and physician is a core value of primary care. Although previous studies suggest that personal continuity is associated with fewer potentially inappropriate prescriptions, evidence on continuity and prescribing in primary care is scarce. We aimed to determine the association between personal continuity and potentially inappropriate prescriptions, which encompasses potentially inappropriate medications (PIMs) and potential prescribing omissions (PPOs), by family physicians among older patients. METHODS: We conducted an observational cohort study using routine care data from patients enlisted in 48 Dutch family practices from 2013 to 2018. All 25,854 patients aged 65 years and older having at least 5 contacts with their practice in 6 years were included. We calculated personal continuity using 3 established measures: the usual provider of care measure, the Bice-Boxerman Index, and the Herfindahl Index. We used the Screening Tool of Older Person's Prescriptions (STOPP) and the Screening Tool to Alert doctors to Right Treatment (START) specific to the Netherlands version 2 criteria to calculate the prevalence of potentially inappropriate prescriptions. To assess associations, we conducted multilevel negative binomial regression analyses, with and without adjustment for number of chronic conditions, age, and sex. RESULTS: The patients' mean (SD) values for the usual provider of care measure, the Bice-Boxerman Continuity of Care Index, and the Herfindahl Index were 0.70 (0.19), 0.55 (0.24), and 0.59 (0.22), respectively. In our population, 72.2% and 74.3% of patients had at least 1 PIM and PPO, respectively; 30.9% and 34.2% had at least 3 PIMs and PPOs, respectively. All 3 measures of personal continuity were positively and significantly associated with fewer potentially inappropriate prescriptions. CONCLUSIONS: A higher level of personal continuity is associated with more appropriate prescribing. Increasing personal continuity may improve the quality of prescriptions and reduce harmful consequences.

Off-label low dose amitriptyline for insomnia disorder: Patient-reported outcomes.

PURPOSE: Low dose amitriptyline is prescribed off-label to improve sleep maintenance in patients with insomnia disorder. Data on treatment outcomes are limited. We aimed to assess patient-reported treatment effect and side effects of low dose amitriptyline for insomnia in routine care data. METHODS: Cross-sectional study: Seven hundred fifty-two consecutive patients with insomnia disorder having sleep maintenance problems were treated in an outpatient sleep clinic with low dose amitriptyline (10-20 mg based on self-titration). Treatment was intended to improve sleep maintenance. Before the planned follow-up consultation (approximately 6 weeks after start treatment) patients completed an online treatment evaluation questionnaire. Treatment (dose, adherence), sleep, fatigue, satisfaction and side effects were assessed by multiple-choice questions with room for free-text elaboration. RESULTS: 53.7% of the patients reported to use amitriptyline up to 10 mg/day, 42.9% used a self-increased dose of mostly 20 mg/day, while 3.5% had discontinued treatment. 73.9% of the total study population reported improvement of sleep maintenance, 31.3% improved sleep onset, 35.2% improved daytime fatigue, and 45.8% reported to be (very) satisfied with treatment results. 66.1% reported at least one side effect. The reported side effects were generally the already known side effects of amitriptyline. CONCLUSION: These patient-reported outcomes support the clinical observations that low dose amitriptyline improves sleep maintenance on the short term and that it is generally well tolerated. This further justifies randomized controlled trials in patients with insomnia disorder and sleep maintenance problems to assess the effectiveness and safety of low dose amitriptyline on the short and long term.

Insomnia management in Dutch general practice: a routine care database study.

OBJECTIVE: To explore insomnia management in general practice, with a focus on sleep medication prescription. DESIGN: Descriptive analysis of anonymized routine general practice care data extracted from electronic medical records (EMRs), including demographics, free text annotations from sleep consultations and sleep medication prescriptions covering one year before up to two years after the registration of the International Classification for Primary Care (ICPC) code P06 'Sleep disturbance'. SETTING: Twenty-one general practices in an urban area of the Netherlands. PATIENTS: Adults (18-85 year) with a first sleep consultation with their GP. OUTCOMES: Documented non-pharmacological and sleep medication treatment. RESULTS: Of the 1,089 patients who consulted their general practitioner (GP) for sleep disturbance for the first time, about 50% had one more sleep consultation during the two years follow-up. Over two years including the first consultation, GPs documented a non-pharmacological intervention for 48.4% of the patients and prescribed sleep medication to 77.0%. 64.6% of the patients received a sleep medication prescription in the first consultation. Among patients receiving medication (N = 838); 59.6% received more than one prescription; 76.8% received one or more short-acting benzodiazepine receptor agonist (BZRA), 39.5% one or more unrecommended drugs and 14.7% >180 pills of BZRAs in two years. CONCLUSION: Although the guidelines advocate non-pharmacological treatment and warn against unwarranted sleep medication, it is still very common in Dutch general practice to prescribe medication, even at the first sleep consultation. Prescriptions frequently include unrecommended and off-label drugs or repeated BZRA prescriptions.

Short statementThere are concerns about the prescription rate and nature of sleep medication prescribed for patients with sleep disturbance. Analysis of routine care data can provide insights in general practitioners (GPs) management of insomnia.3 main statements GPs prescribed sleep medication in the first consultation to 64.6% of the patients who consulted them for sleep disturbance for the first time.Over two years including the first consultation, 48.4% of the patients received a (documented) non-pharmacological intervention, 77.0% a sleep medication prescription.Among patients receiving medication, the majority received short-acting benzodiazepine receptor agonists (BZRAs), but 39.5% (also) received an unrecommended drug.

Testing for coeliac disease rarely leads to a diagnosis: a population-based study.

BACKGROUND: Coeliac disease (CD) has an estimated prevalence of ∼1% in Europe with a significant gap between undiagnosed and diagnosed CD. Active case finding may help to bridge this gap yet the diagnostic yield of such active case finding in general practice by serological testing is unknown. OBJECTIVE: The aim of this study was to determine (1) the frequency of diagnosed CD in the general population, and (2) to investigate the yield of active case finding by general practitioners. METHODS: Electronic medical records of 207.200 patients registered in 49 general practices in The Netherlands in 2016 were analysed. An extensive search strategy, based on International Classification of Primary Care codes, free text and diagnostic test codes was performed to search CD- or gluten-related contacts. RESULTS: The incidence of CD diagnosis in general practice in 2016 was 0.01%. The prevalence of diagnosed CD reported in the general practice in the Netherlands was 0.19%, and considerably higher than previously reported in the general population. During the one year course of the study 0.95% of the population had a gluten-related contact with their GP; most of them (72%) were prompted by gastrointestinal complaints. Serological testing was performed in 66% (n = 1296) of these patients and positive in only 1.6% (n = 21). CONCLUSION: The number of diagnosed CD patients in the Netherlands is substantially higher than previously reported. This suggests that the gap between diagnosed and undiagnosed patients is lower than generally assumed. This may explain that despite a high frequency of gluten-related consultations in general practice the diagnostic yield of case finding by serological testing is low.Key pointsThe diagnostic approach of GPs regarding CD and the diagnostic yield is largely unknownCase finding in a primary health care practice has a low yield of 1.6%CD testing was mostly prompted by consultation for gastrointestinal symptomsThere is a heterogeneity in types of serological test performed in primary care.

Nurse-Guided Internet-Delivered Cognitive Behavioral Therapy for Insomnia in General Practice: Results from a Pragmatic Randomized Clinical Trial.

INTRODUCTION: Guidelines recommend cognitive behavioral therapy for insomnia (CBT-I) as the first line of treatment for insomnia in general practice, but CBT-I is rarely available. Nurse-guided Internet-delivered CBT-I might be a solution to improve access to care. OBJECTIVE: We aimed to determine the effectiveness of nurse-guided Internet-delivered CBT-I (I-CBT-I) on insomnia severity experienced by patients in general practice. METHODS: Nurse-guided I-CBT-I ("i-Sleep") was compared to care-as-usual (and I-CBT-I after 6 months) in 15 participating general practices among 134 patients (≥18 years old) with clinical insomnia symptoms. Assessments took place at 8, 26 and 52 weeks. Primary outcome was self-reported insomnia severity (Insomnia Severity Index) at 8 weeks. Secondary outcomes were sleep diary indices, depression and anxiety symptoms (Hospital Anxiety and Depression Scale), fatigue, daytime consequences of insomnia, sleep medication and adverse events. RESULTS: Two thirds of the 69 intervention patients (n = 47; 68%) completed the whole intervention. At the posttest examination, there were large significant effects for insomnia severity (Cohen's d =1.66), several sleep diary variables (wake after sleep onset, number of awakenings, terminal wakefulness, sleep efficiency, sleep quality) and depression. At 26 weeks there were still significant effects on insomnia severity (d = 1.02) and on total sleep time and sleep efficiency. No significant effects were observed for anxiety, fatigue, daily functioning or sleep medication. No adverse events were reported. CONCLUSIONS: Nurse-guided I-CBT-I effectively reduces insomnia severity among general practice patients. I-CBT-I enables general practitioners to offer effective insomnia care in accordance with the clinical guidelines.

Pressure in dealing with requests for euthanasia or assisted suicide. Experiences of general practitioners.

The majority of Dutch physicians feel pressure when dealing with a request for euthanasia or physician-assisted suicide (EAS). This study aimed to explore the content of this pressure as experienced by general practitioners (GP). We conducted semistructured in-depth interviews with 15 Dutch GPs, focusing on actual cases. The interviews were transcribed and analysed with use of the framework method. Six categories of pressure GPs experienced in dealing with EAS requests were revealed: (1) emotional blackmail, (2) control and direction by others, (3) doubts about fulfilling the criteria, (4) counterpressure by patient's relatives, (5) time pressure around referred patients and (6) organisational pressure. We conclude that the pressure can be attributable to the patient-physician relationship and/or the relationship between the physician and the patient's relative(s), the inherent complexity of the decision itself and the circumstances under which the decision has to be made. To prevent physicians to cross their personal boundaries in dealing with EAS request all these different sources of pressure will have to be taken into account.

Development of hypertension after long-term exposure to static magnetic fields among workers from a magnetic resonance imaging device manufacturing facility.

OBJECTIVE: To assess the association between long-term exposure to static magnetic fields (SMF) in a magnetic resonance imaging (MRI)-manufacturing environment and hypertension. METHODS: In an occupational cohort of male workers (n = 538) of an MRI-manufacturing facility, the first and last available blood pressure measurements from the facility's medical surveillance scheme were associated with modeled cumulative exposure to SMF. Exposure modeling was based on linkage of individual job histories from the facility's personnel records with a facility specific historical job exposure matrix. Hypertension was defined as a systolic pressure of above 140 mm Hg and/or a diastolic blood pressure above 90 mm Hg. Logistic regression models were used to associate cumulative SMF exposure to hypertension while adjusting for age, body mass index and blood pressure at time of first blood pressure measurement. Stratified analysis by exposure duration was performed similarly. RESULTS: High cumulative exposure to SMF (≥ 7.4 K Tesla minutes) was positively associated with development of hypertension (Odds Ratio [OR] 2.32, 95% confidence interval [CI] 1.27 - 4.25, P = 0.006). Stratified analysis showed a stronger association for those with high cumulative SMF exposure within a period up to 10 years (OR 3.96, 95% CI 1.62 - 9.69, P = 0.003), but no significant association was found for (high) cumulative exposure accumulated in a period of 10 or more years. Our findings suggest SMF exposure intensity to be more important than exposure duration for the risk of developing hypertension. CONCLUSIONS: Our data revealed that exposure to high levels of MRI-related SMF during MRI-manufacturing might be associated with developing hypertension.

Effectiveness of a multifaceted implementation strategy compared to usual care on low back pain guideline adherence among general practitioners.

BACKGROUND: To improve patient care, and to reduce unnecessary referrals for diagnostic imaging and medical specialist care for low back pain, an evidence-based guideline for low back pain was developed in the Netherlands in 2010. The current study evaluated the effect of a multifaceted implementation strategy on guideline adherence among Dutch general practitioners. METHODS: The implementation strategy included a multidisciplinary training, provision of educational material and an interactive website for healthcare professionals, supported by a multimedia eHealth intervention for patients with low back pain. Adherence was measured using performance indicators based on 3 months data extracted from the contacts with patients with low back pain recorded in the electronic medical records of participating general practitioners. Performance indicators were compared between two groups: a usual care group and an implementation group. Performance indicators were referrals to consultations with medical specialists, to diagnostic imaging, and to psychosocial and/or occupational physician consultations, and inquiries about psychosocial and occupational risk factors. RESULTS: The electronic medical records of 5130 patient contacts for LBP were analysed; 2453 patient contacts in the usual care group and 2677 patient contacts in the implementation group. Overall, rates of referral and of recorded inquiries regarding psychosocial and occupational risk factors remained low in both groups over time. The only statistically significant difference found was a reduction in the number of referrals to neurologists in the implementation group (from 100 (7%) to 50 (4%)) compared to the usual care group (from 48 (4%) to 50 (4%), (p < 0.01)). There were no other between-group differences in referrals. CONCLUSION: In the short term, the strategy did not result in improved guideline adherence among general practitioners, and it is not recommended for widespread use. However, baseline referral rates in participating practices were already low, possibly leaving only little room for improvement. Inquiries for psychosocial and occupational risk factors remained low and this leaves room for improvement. TRIAL REGISTRATION: This trial is registered in the Netherlands Trial Register (NTR): NTR4329 . Registration date: December 20th, 2013.

Diagnostic behaviour of general practitioners when suspecting Lyme disease: a database study from 2010-2015.

BACKGROUND: Due to the raised public awareness of Lyme Borreliosis (LB), its increased incidence and the increased availability of serological tests, the demand for diagnostic testing on LB has increased. This may affect the diagnostic behaviour of general practitioners (GPs). Aim of our study was to describe GPs' diagnostic behaviour when suspecting LB. METHODS: In this descriptive study from January 2010 to June 2015, we used the anonymized electronic medical records of 56,996 patients registered in 12 general practices in Amsterdam, The Netherlands. The target population was identified by means of an extensive search strategy, based on International Classification of Primary Care (ICPC-1) codes, free text and diagnostic test codes. All contacts related to LB were included in the analysis. RESULTS: 2311 patients were included, accounting for 3861 LB contacts and 2619 LB episodes. The distribution of LB contacts showed annual peaks during spring and summer. Serological testing was performed in 36.4% of LB episodes and was mostly requested in patients presenting with general symptoms (71.4%). Unnecessary testing often occurred and only 5.9% of the tests turned out to be positive by immunoblot. From January 2010 to June 2015, no significant differences were found in the number of requested serological tests. The level of serological testing during LB episodes differed significantly between the general practices (19.2% to 75.8%). CONCLUSIONS: Contrary to clinical guidelines, GPs regularly requested serology even when there was a low suspicion of LB. The development of an easy-to-use diagnostic algorithm may decrease overuse of diagnostic tests and thereby reduce overtreatment of LB.

Modeled and Perceived Exposure to Radiofrequency Electromagnetic Fields From Mobile-Phone Base Stations and the Development of Symptoms Over Time in a General Population Cohort.

We assessed associations between modeled and perceived exposure to radiofrequency electromagnetic fields (RF-EMF) from mobile-phone base stations and the development of nonspecific symptoms and sleep disturbances over time. A population-based Dutch cohort study, the Occupational and Environmental Health Cohort Study (AMIGO) (n = 14,829; ages 31-65 years), was established in 2011/2012 (T0), with follow-up of a subgroup (n = 3,992 invited) in 2013 (T1; n = 2,228) and 2014 (T2; n = 1,740). We modeled far-field RF-EMF exposure from mobile-phone base stations at the home addresses of the participants using a 3-dimensional geospatial model (NISMap). Perceived exposure (0 = not at all; 6 = very much), nonspecific symptoms, and sleep disturbances were assessed by questionnaire. We performed cross-sectional and longitudinal analyses, including fixed-effects regression. We found small correlations between modeled and perceived exposure in AMIGO participants at baseline (n = 14,309; rSpearman = 0.10). For 222 follow-up participants, modeled exposure increased substantially (>0.030 mW/m2) between T0 and T1. This increase in modeled exposure was associated with an increase in perceived exposure during the same time period. In contrast to modeled RF-EMF exposure from mobile-phone base stations, perceived exposure was associated with higher symptom reporting scores in both cross-sectional and longitudinal analyses, as well as with sleep disturbances in cross-sectional analyses.

Hearing loss associated with repeated MRI acquisition procedure-related acoustic noise exposure: an occupational cohort study.

OBJECTIVE: To study the effects of repeated exposure to MRI-related acoustic noise during image acquisition procedures (scans) on hearing. METHODS: A retrospective occupational cohort study was performed among workers of an MRI manufacturing facility (n=474). Longitudinal audiometry data from the facility's medical surveillance scheme collected from 1973 to 2010 were analysed by studying the association of cumulative exposure to MRI-related acoustic noise from voluntary (multiple) MRI scans and the hearing threshold of the volunteer. RESULTS: Repeated acoustic noise exposure during volunteer MRI scans was found to be associated with a small exposure-dependent increased rate change of hearing threshold level (dB/year), but the association was only found related to the number of voluntary MRI scans and not to modelled cumulative noise exposure (dB*hour) based on MRI-system type. The increased rate change of hearing threshold level was found to be statistically significant for the frequencies 500, 1000, 2000, 3000 and 4000 Hz in the right ear. CONCLUSIONS: From our longitudinal cohort study, it appeared that exposure to noise from voluntarily MRI scans may have resulted in a slight amount of hearing loss. Mandatory use of hearing protection might have prevented more severe hearing loss. Lack of consistency in findings between the left and right ears and between the two exposure measures prohibits definitive conclusions. Further research that addresses the study's methodological limitations is warranted to corroborate our findings.

Occupational exposure and amyotrophic lateral sclerosis in a prospective cohort.

OBJECTIVE: To prospectively study suspected occupational risk factors for amyotrophic lateral sclerosis (ALS). METHODS: For this case-cohort analysis within the prospective Netherlands Cohort Study, 58 279 men and 62 573 women aged 55-69 years at enrolment in 1986 were followed up for 17.3 years on ALS mortality. Information on occupational history and potential confounders were collected at baseline through a self-administered questionnaire and entered for a random subcohort (2092 men and 2074 women) and ALS deaths (76 men and 60 women). Occupational exposure to solvents, pesticides, metals, extremely low frequency magnetic fields (ELF-MFs) and electrical shocks was estimated by means of job exposure matrices (JEMs). Associations between ever/never occupationally exposed and cumulative exposure and ALS mortality were analysed by gender using Cox regression. RESULTS: Occupational exposure to ELF-MF showed a possible association with ALS mortality among men: HR for ever holding a job with high exposure versus background 2.19 (95% (CI): 1.02 to 4.73) and HR for the highest tertile of cumulative exposure versus background 1.93 (95% CI 1.05 to 3.55). INTERPRETATION: These results strengthen the evidence suggesting a positive association between ELF-MF exposure and ALS. We did not replicate earlier positive findings for other occupational exposures.

Exposure to static magnetic fields and risk of accidents among a cohort of workers from a medical imaging device manufacturing facility.

PURPOSE: To study the association between occupational MRI-related static magnetic fields (SMF) exposure and the occurrence of accidents. METHODS: Recent and career SMF exposure was assessed by linking a retrospective job exposure matrix to payroll based job histories, for a cohort of (former) workers of an imaging device manufacturing facility in the Netherlands. Occurrence of accidents was collected through an online questionnaire. Self-reported injuries due to accidents in the past 12 months, and the first (near) traffic accident while commuting to work and from work were analyzed with logistic regression and discrete-time survival analyses, respectively. RESULTS: High recent SMF exposure was associated with an increased risk of accidents leading to injuries [odds ratio (OR) 4.16]. For high recent and career SMF exposure, an increased risk was observed for accidents resulting in physician-treated injuries (OR 5.78 and 2.79, respectively) and an increased lifetime risk of (near) accidents during commute to work (hazard ratios 2.49 and 2.45, respectively), but not from work. CONCLUSION: We found an association between MRI-related occupational SMF exposure and an increased risk of accidents leading to injury, and for commute-related (near) accidents during the commute from home to work. Further research into health effects of (long-term) SMF exposure is warranted to corroborate our findings.

Cost-effectiveness of i-Sleep, a guided online CBT intervention, for patients with insomnia in general practice: protocol of a pragmatic randomized controlled trial.

BACKGROUND: Insomnia is a highly prevalent disorder causing clinically significant distress and impairment. Furthermore, insomnia is associated with high societal and individual costs. Although cognitive behavioural treatment for insomnia (CBT-I) is the preferred treatment, it is not used often. Offering CBT-I in an online format may increase access. Many studies have shown that online CBT for insomnia is effective. However, these studies have all been performed in general population samples recruited through media. This protocol article presents the design of a study aimed at establishing feasibility, effectiveness and cost-effectiveness of a guided online intervention (i-Sleep) for patients suffering from insomnia that seek help from their general practitioner as compared to care-as-usual. METHODS/DESIGN: In a pragmatic randomized controlled trial, adult patients with insomnia disorder recruited through general practices are randomized to a 5-session guided online treatment, which is called "i-Sleep", or to care-as-usual. Patients in the care-as-usual condition will be offered i-Sleep 6 months after inclusion. An ancillary clinician, known as the psychological well-being practitioner who works in the GP practice (PWP; in Dutch: POH-GGZ), will offer online support after every session. Our aim is to recruit one hundred and sixty patients. Questionnaires, a sleep diary and wrist actigraphy will be administered at baseline, post intervention (at 8 weeks), and at 6 months and 12 months follow-up. Effectiveness will be established using insomnia severity as the main outcome. Cost-effectiveness and cost-utility (using costs per quality adjusted life year (QALY) as outcome) will be conducted from a societal perspective. Secondary measures are: sleep diary, daytime consequences, fatigue, work and social adjustment, anxiety, alcohol use, depression and quality of life. DISCUSSION: The results of this trial will help establish whether online CBT-I is (cost-) effective and feasible in general practice as compared to care-as-usual. If it is, then quality of care might be increased because implementation of i-Sleep makes it easier to adhere to insomnia guidelines. Strengths and limitations are discussed. TRIAL REGISTRATION: Netherlands Trial register NTR 5202 (registered April 17(st) 2015).

Novel exposure units for at-home personalized testing of electromagnetic sensibility.

Previous experimental studies on electromagnetic hypersensitivity have been criticized regarding inflexibility of choice of exposure and of study locations. We developed and tested novel portable exposure units that can generate different output levels of various extremely low frequency magnetic fields (ELF-MF; 50 Hz field plus harmonics) and radiofrequency electromagnetic fields (RF-EMF). Testing was done with a group of healthy volunteers (n = 25 for 5 ELF-MF and n = 25 for 5 RF-EMF signals) to assess if units were indeed able to produce double-blind exposure conditions. Results substantiated that double-blind conditions were met; on average participants scored 50.6% of conditions correct on the ELF-MF, and 50.0% on the RF-EMF unit, which corresponds to guessing probability. No cues as to exposure conditions were reported. We aim to use these units in a future experiment with subjects who wish to test their personal hypothesis of being able to sense or experience when being exposed to EMF. The new units allow for a high degree of flexibility regarding choice of applied electromagnetic signal, output power level and location (at home or another environment of subjects' choosing).

Occupational exposure to extremely low-frequency magnetic fields and electrical shocks and acute myeloid leukemia in four Nordic countries.

OBJECTIVE: We studied the association between occupational exposure to extremely low-frequency magnetic fields (ELF-MF) and electrical shocks and acute myeloid leukemia (AML) in the Nordic Occupational Cancer cohort (NOCCA). METHODS: We included 5,409 adult AML cases diagnosed between 1961 and 2005 in Finland, Iceland, Norway, and Sweden and 27,045 controls matched by age, sex, and country. Lifetime occupational ELF-MF exposure and risk of electrical shocks were assigned to jobs reported in the censuses using job-exposure matrices. We estimated hazard ratios (HRs) and 95 % confidence intervals (95 % CIs) using conditional logistic regression adjusted for concurrent occupational exposures relevant for AML risk (e.g., benzene, ionizing radiation). We conducted sensitivity analyses with different assumptions to assess the robustness of our results. RESULTS: Approximately 40 % of the subjects were ever occupationally exposed to low levels and 7 % to high levels of ELF-MF, whereas 18 % were ever at low risk and 15 % at high risk of electrical shocks. We did not observe an association between occupational exposure to neither ELF-MF nor electrical shocks and AML. The HR was 0.88 (95 % CI 0.77-1.01) for subjects with high levels of ELF-MF exposure and 0.94 (95 % CI 0.85-1.05) for subjects with high risk of electrical shocks as compared to those with background-level exposure. Results remained materially unchanged in sensitivity analyses with different assumptions. CONCLUSION: Our results do not support an association between occupational ELF-MF or electric shock exposure and AML.

Simultaneous exposure to MRI-related static and low-frequency movement-induced time-varying magnetic fields affects neurocognitive performance: A double-blind randomized crossover study.

PURPOSE: This experimental study aims to separate neurocognitive effects resulting from exposure to static magnetic stray fields (SMF) alone and the combination of SMF and low-frequency movement-induced time-varying magnetic fields (TVMF) using a 7 Tesla (T) MRI scanner in stand-by mode. METHODS: In a double-blind randomized crossover experiment, 36 healthy volunteers underwent four sessions, two exposed conditions, and two corresponding sham conditions. The exposure conditions were in front of the scanner bore and consisted of 1.0 T SMF with or without 2.4 T/s TVMF, induced by standardized head movements before each of the five neurocognitive tasks. These specific tasks were selected because previous experiments showed negative effects of SMF + TVMF exposure on test performance. RESULTS: Exposure to SMF in combination with TVMF decreased verbal memory performance significantly and changed visual acuity. Similarly, attention and concentration were negatively affected with borderline significance. Exposure to SMF only did not have significant effects on the performance on any of the tasks. CONCLUSION: Neurocognitive effects were only observed when simultaneously exposed to SMF and TVMF from a 7 T MRI scanner. Therefore, exposure to TVMF seems essential in eliciting the neurocognitive effects in our present study and, presumably, previous experiments.

Does assessment of personal exposure matter during experimental neurocognitive testing in MRI-related magnetic fields?

PURPOSE: To determine whether the use of quantitative personal exposure measurements in experimental research would result in better estimates of the associations between static and time-varying magnetic field exposure and neurocognitive test performance than when exposure categories were based solely on distance to the magnetic field source. METHODS: In our original analysis, based on distance to the magnet of a 7 T MRI scanner, an effect of exposure to static magnetic fields was observed. We performed a sensitivity analysis of test performance on a reaction task and line bisection task with different exposure measures that were derived from personal real-time measurements. RESULTS: The exposure measures were highly comparable, and almost all models resulted in significant associations between exposure to time-varying magnetic fields within a static magnetic field and performance on a reaction and line bisection task. CONCLUSION: In a controlled experimental setup, distance to the bore is a good proxy for personal exposure when placing subjects at fixed positions with standardized head movements in the magnetic stray fields of a 7 T MRI. Use of a magnetic field dosimeter is, however, important for estimating quantitative exposure response associations.

Occupational exposures and risk of dementia-related mortality in the prospective Netherlands Cohort Study.

BACKGROUND: Occupational exposures may be associated with non-vascular dementia. METHODS: We analyzed the effects of occupational exposures to solvents, pesticides, metals, extremely low frequency magnetic fields (ELF-MF), electrical shocks, and diesel motor exhaust on non-vascular dementia related mortality in the Netherlands Cohort Study (NLCS). Exposures were assigned using job-exposure matrices. After 17.3 years of follow-up, 682 male and 870 female cases were available. Analyses were performed using Cox regression. RESULTS: Occupational exposure to metals, chlorinated solvents and ELF-MF showed positive associations with non-vascular dementia among men, which seemed driven by metals (hazard ratio ever high vs. background exposure: 1.35 [0.98-1.86]). Pesticide exposure showed statistically significant, inverse associations with non-vascular dementia among men. We found no associations for shocks, aromatic solvents, and diesel motor exhaust. CONCLUSIONS: Consistent positive associations were found between occupational exposure to metals and non-vascular dementia. The finding on pesticides is not supported in the overall literature.

Occupational extremely low-frequency magnetic field exposure and selected cancer outcomes in a prospective Dutch cohort.

PURPOSE: To investigate the association between exposure to occupational extremely low-frequency magnetic fields (ELF-MF) and the risk of a priori selected cancer outcomes within the prospective Netherlands Cohort Study. METHODS: 120,852 men and women aged 55-69 years at time of enrollment in 1986 were followed up (17.3 years) for incident lung, breast and brain cancer, and hemato-lymphoproliferative malignancies. Information on occupational history and potential confounders such as sex, age, smoking, alcohol use, and attained educational level were collected at baseline through a self-administered questionnaire. Occupational ELF-MF exposure was assigned with a job-exposure matrix. Using a case-cohort approach, associations with cancer incidence were analyzed with Cox regression stratified by sex, using three exposure metrics: (1) ever had a job with low or high exposure to ELF-MF versus background, (2) duration of exposure, and (3) cumulative exposure. RESULTS: None of the exposure metrics showed an effect on incidence for lung, breast, and brain cancer, nor any of the assessed subtypes in men and women. Of the hemato-lymphoproliferative malignancies in men, ever high exposed to ELF-MF showed a significant association with acute myeloid leukemia (AML) [hazard ratio (HR) 2.15; 95 % confidence interval (CI) 1.06-4.35] and follicular lymphoma (FL) (HR 2.78; 95 % CI 1.00-5.77). Cumulative exposure to ELF-MF showed a significant, positive association with FL but not AML among men. CONCLUSIONS: In this large prospective cohort study, we found some indications of an increased risk of AML and FL among men with occupational ELF-MF exposure. These findings warrant further investigation.