Bypassing the selection rule in choosing controls for a case-control study

Objectives It has been argued that in case–control studies, controls should be drawn from the base population that gives rise to the cases. In designing a study of occupational injury and risks arising from long-term illness and prescribed medication, we lacked data on subjects' occupation, without which employed cases (typically in manual occupations) would be compared with controls from the general population, including the unemployed and a higher proportion of white-collar professions. Collecting the missing data on occupation would be costly. We estimated the potential for bias if the selection rule were ignored. Methods: We obtained published estimates of the frequencies of several exposures of interest (diabetes, mental health problems, asthma, coronary heart disease) in the general population, and of the relative risks of these diseases in unemployed versus employed individuals and in manual versus non-manual occupations. From these we computed the degree of over- or underestimation of exposure frequencies and exposure ORs if controls were selected from the general population. Results: The potential bias in the OR was estimated as likely to fall between an underestimation of 14% and an overestimation of 36.7% (95th centiles). In fewer than 6% of simulations did the error exceed 30%, and in none did it reach 50%. Conclusions: For the purposes of this study, in which we were interested only in substantial increases in risk, the potential for selection bias was judged acceptable. The rule that controls should come from the same base population as cases can justifiably be broken, at least in some circumstances. <br/

Mortality from infectious pneumonia in metal workers: a comparison with deaths from asthma in occupations exposed to respiratory sensitizers

Introduction: national analyses of mortality in England and Wales have repeatedly shown excess deaths from pneumonia in welders. During 1979-1990 the excess was attributable largely to deaths from lobar pneumonia and pneumonias other than bronchopneumonia, limited to working-aged men, and apparent in other metal fume-exposed occupations. We assessed findings for 1991-2000 and compared the mortality pattern with that from asthma in occupations exposed to known respiratory sensitizers.Methods: the Office of National Statistics supplied data on deaths by underlying cause among men aged 16-74 years in England and Wales during 1991-2000, including age and last held occupation. We abstracted data on pneumonia for occupations with exposure to metal fume and on asthma for occupations commonly reported to surveillance schemes as at risk of occupational asthma. We estimated expected numbers of deaths by applying age-specific proportions of deaths by cause in the population to the total deaths by age in each occupational group. Observed and expected numbers were compared for each cause of death.Results: among working-aged men in metal fume-exposed occupations we found excesses of mortality from pneumococcal and lobar pneumonia (54 deaths vs. 27.3 expected) and from pneumonias other than bronchopneumonia (71 vs. 52.4), but no excess from these causes at older ages, or from bronchopneumonia at any age. The attributable mortality from metal fume (45.3 excess deaths) compared with an estimated 62.6 deaths from occupational asthma.Conclusion: exposure to metal fume is a material cause of occupational mortality. The hazard deserves far more attention than it presently receive

Coronary heart disease, hypertension and use of biomass fuel among women: Comparative cross-sectional study

Objectives: To explore the associations of hypertension and coronary heart disease (CHD) with use of biomass fuel for cooking.Design: Comparative cross-sectional study.Setting: Rural villages in Sindh, Pakistan.Participants: Women aged ≥40 years who had used biomass fuel for cooking for at least the last year (n=436), and a comparison group (n=414) who had cooked only with non-biomass fuel during the last year were recruited through door-to-door visits. None of those who were invited to take part declined.Primary and secondary outcome measures: Hypertension was determined from blood pressure measurements and use of medication. CHD was assessed by three measures: history of angina (Rose angina questionnaire), previous history of \u27heart attack\u27, and definite or probable changes of CHD on ECG. Potentially confounding risk factors were ascertained by questionnaire and anthropometry. Associations of hypertension and CHD with use of biomass and other risk factors were assessed by logistic regression, and summarised by ORs with 95% CIs.Results: After adjustment for potential confounders, there was no association of hypertension (OR: 1.0, 95% CI 0.8 to 1.4) angina (OR: 1.0, 95% CI 0.8 to 1.4), heart attack (OR: 1.2, 95% 0.7 to 2.2) or ECG changes of CHD (OR: 0.8, 95% CI 0.6 to 1.2) with current use of biomass for cooking. Nor were any associations apparent when analyses were restricted to long-term (≥10 years) users and non-users of biomass fuel.Conclusions: A linked air monitoring study indicated substantially higher airborne concentrations of fine particulate matter in kitchens where biomass was used for cooking. It is possible that associations with CHD and hypertension were missed because most of the comparison group had used biomass for cooking at some time in the past, and risk remains elevated for many years after last exposure

A IMPORTÂNCIA DA ESTATÍSTICA NA PESQUISA EM SAÚDE

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Tradução, adaptação e validação do Cultural and Psychosocial Influences on Disability (CUPID) Questionnaire para uso no Brasil

The paper describes the adaptation and testing of the Cultural and Psychosocial Influences on Disability Questionnaire for use in Portuguese. The cross-cultural adaptation followed the steps of translation, back-translation, evaluation of the translations by a committee of judges, and then piloting of the pre-final version. This was performed in a sample of 40 nursing staff from the Hospital at the University of São Paulo. Adjustments were made after review of the translations by the committee of judges (CVI&#8804; 80%). The pilot study was used to test whether questions could be satisfactorily understood and completed (&#8805; 85% of subjects). The Brazilian version of the Questionnaire is an adequate instrument for the ascertainment of occupational activities, psychosocial aspects of work, musculoskeletal symptoms and associated disabilities in nursing staff.El objetivo de este estudio fue describir la adaptación y validación del cuestionario Investigación Internacional sobre las Influencias Físicas, Culturales y Psicosociales en los Síntomas Musculares Esqueléticos e Incapacidades Asociadas, para la lengua portuguesa. El proceso de adaptación transcultural siguió las etapas de traducción, retrotraducción, evaluación de las traducciones por un comité de jueces y, en seguida, la realización de una prueba de la versión prefinal. Se utilizó una muestra de 40 trabajadores de enfermería del Hospital de la Universidad de Sao Paulo. Las adaptaciones fueron hechas después de someterlo al comité de jueces (IVC&#8804;80%). La prueba piloto comprobó la comprensión de las preguntas a través del llenado (&#8805;85% de los sujetos). La versión brasileña del cuestionario mostró ser un instrumento adecuado para la verificación de las actividades profesionales, aspectos psicosociales del trabajo y síntomas osteomusculares, asociados a incapacidad entre los trabajadores de enfermería.O objetivo deste estudo foi descrever a adaptação e validação do Questionário Pesquisa Internacional sobre as Influências Físicas, Culturais e Psicossociais nos Sintomas Musculoesqueléticos e Incapacidades Associadas, para a língua portuguesa. O processo de adaptação transcultural seguiu as etapas de tradução, retrotradução, avaliação das traduções por um comitê de juízes e, em seguida, teste da versão pré-final. Utilizou-se amostra de 40 trabalhadores de enfermagem do Hospital da Universidade de São Paulo. Adaptações foram feitas após a submissão ao comitê de juízes (IVC&#8804;80%). O teste piloto testou a compreensão das questões pelo seu preenchimento (&#8805;85% dos sujeitos). A versão brasileira do Questionário mostrou ser instrumento adequado para a verificação das atividades profissionais, aspectos psicossociais do trabalho e sintomas osteomusculares, associados à incapacidade entre os trabalhadores de enfermagem

The History, Development and Impact of Computed Imaging in Neurological Diagnosis and Neurosurgery: CT, MRI, and DTI

A steady series of advances in physics, mathematics, computers and clinical imaging science have progressively transformed diagnosis and treatment of neurological and neurosurgical disorders in the 115 years between the discovery of the X-ray and the advent of high resolution diffusion based functional MRI. The story of the progress in human terms, with its battles for priorities, forgotten advances, competing claims, public battles for Nobel Prizes, and patent priority litigations bring alive the human drama of this remarkable collective achievement in computed medical imaging

Low back pain among office workers in three Spanish-speaking countries: Findings from the CUPID study

Artículo científicoObjectives—To assess differences in the prevalence and incidence of low back pain (LBP) and associated disability among office workers in Costa Rica, Nicaragua and Spain. Methods—Data were collected at baseline (n=947, 93% response) in November 2007 and at follow-up after 12 months (n=853, 90% response). Six outcome measures were examined: baseline prevalence of (1) LBP in past 12 months, (2) LBP in past month, and (3) disabling LBP in past month; and at follow-up: (4) incidence of new LBP in the past month, (5) new disabling LBP, and (6) persistent LBP. Differences in prevalence by country were characterized by odd ratios (ORs) with 95% confidence intervals (95%CIs), before and after adjustment for covariates. Results—Prevalence of LBP in the past month among office employees in Costa Rica (46.0%) and Nicaragua (44.2%) was higher than in Spain (33.6%). Incidence of new LBP was 37.0% in Nicaragua (OR=2.49; 95% CI: 1.57-3.95), 14.9% in Costa Rica (OR=0.74; 95% CI: 0.41-1.34), and 19.0% in Spain (reference). Incidence of new disabling LBP was higher in Nicaragua, 17.2%(OR=2.49; 95% CI: 1.43-4.34) and Costa Rica, 13.6% (OR=1.89; 95% CI: 1.03-3.48) than Spain (7.7%), while persistence of LBP was higher only in Nicaragua. Conclusions—Prevalence of LBP and disabling LBP was higher in Costa Rican and Nicaraguan office workers than in Spain, but incidence was higher mainly in Nicaragua. Measured sociodemographic, job-related and health-related variables only partly explained the differences between countries, and further research is needed to explore reasons for the remaining differences

MultiTex RCT - A multifaceted intervention package for protection against cotton dust exposure among textile workers - A cluster randomized controlled trial in Pakistan: Study protocol

Background: In the Pakistani textile industry the prevalence of workplace respiratory illnesses, including byssinosis, is high. The MultiTex RCT study aims to determine the effectiveness of a multifaceted intervention package in reducing dust levels in cotton mills, decreasing the frequency of respiratory symptoms among cotton textile workers, and improving their lung function.Methods/design: We will conduct a cluster-randomized controlled trial at 28 textile mills in Karachi. The intervention will comprise: training in occupational health for all workers and managers reinforced by regular refresher sessions; the formation of workplace committees to draw up, agree and promote a health and safety plan that includes wet mopping, safe disposal of cotton dust, and the use of simple face-masks, as well as further publicity about the risks from cotton dust; and provision of adequate supplies of face-masks to support the health and safety plan. Participating mills will be randomized to intervention and control arms following a baseline survey. The impact of the intervention will be determined through follow-up surveys conducted at 3, 12 and 18 months. Data collection in the surveys will include spirometry, questionnaire-based interviews and cotton-dust measurements.Discussion: If successful, the study may pave the way for simple, low-cost interventions that can help reduce cotton-dust levels in textile mills, and improve the respiratory health of textile workers in developing countries such as Pakistan

Marine Boundary Layer Clouds Associated with Coastally Trapped Disturbances: Observations and Model Simulations

This work has been accepted to Journal of Atmospheric Sciences. The AMS does not guarantee that the copy provided here is an accurate copy of the final published work.Modeling marine low clouds and fog in coastal environments remains an outstanding challenge due to the inherently complex ocean–land–atmosphere system. This is especially important in the context of global circulation models due to the profound radiative impact of these clouds. This study utilizes aircraft and satellite measurements, in addition to numerical simulations using the Weather Research and Forecasting (WRF) Model, to examine three well-observed coastally trapped disturbance (CTD) events from June 2006, July 2011, and July 2015. Cloud water-soluble ionic and elemental composition analyses conducted for two of the CTD cases indicate that anthropogenic aerosol sources may impact CTD cloud decks due to synoptic-scale patterns associated with CTD initiation. In general, the dynamics and thermodynamics of the CTD systems are well represented and are relatively insensitive to the choice of physics parameterizations; however, a set of WRF simulations suggests that the treatment of model physics strongly influences CTD cloud field evolution. Specifically, cloud liquid water path (LWP) is highly sensitive to the choice of the planetary boundary layer (PBL) scheme; in many instances, the PBL scheme affects cloud extent and LWP values as much as or more than the microphysics scheme. Results suggest that differences in the treatment of entrainment and vertical mixing in the Yonsei University (nonlocal) and Mellor–Yamada–Janjić (local) PBL schemes may play a significant role. The impact of using different driving models—namely, the North American Mesoscale Forecast System (NAM) 12-km analysis and the NCEP North American Regional Reanalysis (NARR) 32-km products—is also investigated