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1.
Am J Public Health ; 112(8): 1151-1160, 2022 08.
Artigo em Inglês | MEDLINE | ID: mdl-35830672

RESUMO

Life expectancy figures for countries and population segments are increasingly being reported to more decimal places and used as indicators of the strengths or failings of countries' health and social systems. Reports seldom quantify their intrinsic statistical imprecision or the age-specific numbers of deaths that determine them. The SE formulas available to compute imprecision are all model based. This note adds a more intuitive data-based SE method and extends the jackknife to the analysis of event rates more generally. It also describes the relationships between the magnitude of the SE and the numbers of person-years and deaths on which it is based. These relationships can help quantify the statistical noise present in published year-to-year differences in life expectancies, as well as in same-year differences between or within countries. Agencies and investigators are encouraged to use one of these SEs to report the imprecision of life expectancy numbers and to tailor the number of decimal places accordingly. (Am J Public Health. 2022;112(8):1151-1160. https://doi.org/10.2105/AJPH.2022.306805).


Assuntos
Expectativa de Vida , Bases de Dados Factuais , Humanos
2.
Am J Epidemiol ; 190(12): 2664-2670, 2021 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-34151374

RESUMO

Epidemiologists commonly use an adjusted hazard ratio or incidence density ratio, or a standardized mortality ratio, to measure a difference in all-cause mortality rates. They seldom translate it into an age-, time-, or probability-based measure that would be easier to communicate and to relate to. Several articles have shown how to translate from a standardized mortality ratio or hazard ratio to a longevity difference, a difference in actuarial ages, or a probability of being outlived. In this paper, we describe the settings where these translations are and are not appropriate and provide some of the heuristics behind the formulae. The tools that yield differences in "effective age" and in longevity are applicable when both 1) the mortality rate ratio (hazard ratio) is constant over age and 2) the rates themselves are log-linear in age. The "probability/odds of being outlived" metric is applicable whenever the first condition holds, and thus it provides no direct information on the magnitude of the effective age/longevity difference.


Assuntos
Expectativa de Vida/tendências , Longevidade , Modelos Estatísticos , Mortalidade/tendências , Adulto , Fatores Etários , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Probabilidade , Modelos de Riscos Proporcionais , Fatores Sexuais , Fatores de Tempo
4.
BMC Med Res Methodol ; 21(1): 83, 2021 04 24.
Artigo em Inglês | MEDLINE | ID: mdl-33894761

RESUMO

BACKGROUND: Generalized linear mixed models (GLMMs), typically used for analyzing correlated data, can also be used for smoothing by considering the knot coefficients from a regression spline as random effects. The resulting models are called semiparametric mixed models (SPMMs). Allowing the random knot coefficients to follow a normal distribution with mean zero and a constant variance is equivalent to using a penalized spline with a ridge regression type penalty. We introduce the least absolute shrinkage and selection operator (LASSO) type penalty in the SPMM setting by considering the coefficients at the knots to follow a Laplace double exponential distribution with mean zero. METHODS: We adopt a Bayesian approach and use the Markov Chain Monte Carlo (MCMC) algorithm for model fitting. Through simulations, we compare the performance of curve fitting in a SPMM using a LASSO type penalty to that of using ridge penalty for binary data. We apply the proposed method to obtain smooth curves from data on the relationship between the amount of pack years of smoking and the risk of developing chronic obstructive pulmonary disease (COPD). RESULTS: The LASSO penalty performs as well as ridge penalty for simple shapes of association and outperforms the ridge penalty when the shape of association is complex or linear. CONCLUSION: We demonstrated that LASSO penalty captured complex dose-response association better than the Ridge penalty in a SPMM.


Assuntos
Teorema de Bayes , Simulação por Computador , Humanos , Modelos Lineares , Cadeias de Markov , Método de Monte Carlo
5.
Nephrol Dial Transplant ; 34(11): 1941-1949, 2019 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-31329952

RESUMO

BACKGROUND: High discontinuation rates remain a challenge for home hemodialysis (HHD) and peritoneal dialysis (PD). We compared technique failure risks among Canadian patients receiving HHD and PD. METHODS: Using the Canadian Organ Replacement Register, we studied adult patients who initiated HHD or PD within 1 year of beginning dialysis between 2000 and 2012, with follow-up until 31 December 2013. Technique failure was defined as a transfer to any alternative modality for a period of ≥60 days. Technique survival between HHD and PD was compared using a Fine and Gray competing risk model. We also examined the time dependence of technique survival, the association of patient characteristics with technique failure and causes of technique failure. RESULTS: Between 2000 and 2012, 15 314 patients were treated with a home dialysis modality within 1 year of dialysis initiation: 14 461 on PD and 853 on HHD. Crude technique failure rates were highest during the first year of therapy for both home modalities. During the entire period of follow-up, technique failure was lower with HHD compared with PD (adjusted hazard ratio = 0.79; 95% confidence interval 0.69-0.90). However, the relative technique failure risk was not proportional over time and the beneficial association with HHD was only apparent after the first year of dialysis. Comparisons also varied among subgroups and the superior technique survival associated with HHD relative to PD was less pronounced in more recent years and among older patients. Predictors of technique failure also differed between modalities. While obesity, smoking and small facility size were associated with higher technique failure in both PD and HHD, the association with age and gender differed. Furthermore, the majority of discontinuation occurred for medical reasons in PD (38%), while the majority of HHD patients experienced technique failure due to social reasons or inadequate resources (50%). CONCLUSIONS: In this Canadian study of home dialysis patients, HHD was associated with better technique survival compared with PD. However, patterns of technique failure differed significantly among these modalities. Strategies to improve patient retention across all home dialysis modalities are needed.


Assuntos
Hemodiálise no Domicílio/mortalidade , Hemodiálise no Domicílio/métodos , Falência Renal Crônica/mortalidade , Falência Renal Crônica/terapia , Diálise Peritoneal/mortalidade , Diálise Peritoneal/métodos , Adulto , Idoso , Canadá , Estudos de Coortes , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Fatores de Risco , Falha de Tratamento
6.
Stat Med ; 38(26): 5113-5119, 2019 11 20.
Artigo em Inglês | MEDLINE | ID: mdl-31452226

RESUMO

Small-sample confidence intervals for the mean of a Poisson distribution have been used since the 1930s. They can be computed by trial and error, or using a computation-saving link that few are aware of and that, even if they are, is neither intuitive nor easy to remember. I trace how and why this link has been used, even if the basis for it has been lost or ignored. I promote a direct and more meaningful link that can be easily used today without having to resort to tables or approximations suited to hand calculators. More importantly, this (time-based) link is instructive and intuitive, and thus more easily derived and understood.


Assuntos
Estudos Epidemiológicos , Distribuição de Poisson , Tamanho da Amostra , Algoritmos , Intervalos de Confiança , Modelos Estatísticos , Software , Fatores de Tempo
7.
BMC Med Res Methodol ; 19(1): 209, 2019 11 15.
Artigo em Inglês | MEDLINE | ID: mdl-31730446

RESUMO

BACKGROUND: The analysis of twin data presents a unique challenge. Second-born twins on average weigh less than first-born twins and have an elevated risk of perinatal mortality. It is not clear whether the risk difference depends on birth order or their relative birth weight. This study evaluates the association between birth order and perinatal mortality by birth order-specific weight difference in twin pregnancies. METHODS: We adopt generalized additive mixed models (GAMMs) which are a flexible version of generalized linear mixed models (GLMMs), to model the association. Estimation of such models for correlated binary data is challenging. We compare both Bayesian and likelihood-based approaches for estimating GAMMs via simulation. We apply the methods to the US matched multiple birth data to evaluate the association between twins' birth order and perinatal mortality. RESULTS: Perinatal mortality depends on both birth order and relative birthweight. Simulation results suggest that the Bayesian method with half-Cauchy priors for variance components performs well in estimating all components of the GAMM. The Bayesian results were sensitive to prior specifications. CONCLUSION: We adopted a flexible statistical model, GAMM, to precisely estimate the perinatal mortality risk differences between first- and second-born twins whereby birthweight and gestational age are nonparametrically modelled to explicitly adjust for their effects. The risk of perinatal mortality in twins was found to depend on both birth order and relative birthweight. We demonstrated that the Bayesian method estimated the GAMM model components more reliably than the frequentist approaches.


Assuntos
Ordem de Nascimento , Peso ao Nascer , Mortalidade Perinatal , Gêmeos/estatística & dados numéricos , Teorema de Bayes , Feminino , Idade Gestacional , Humanos , Recém-Nascido , Funções Verossimilhança , Modelos Lineares , Masculino
8.
J Natl Compr Canc Netw ; 16(9): 1065-1073, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-30181418

RESUMO

Objectives: The primary objective of this study was to identify the predictors of new-onset psychological distress available in routinely collected administrative health databases for women diagnosed with breast cancer. The secondary objective was to explore whether the predictors vary based on the period of cancer care. Methods: A population-based cohort study followed 16,495 female patients with newly diagnosed breast cancer who did not experience psychological distress during the 14 months before breast cancer surgery. The incidence of psychological distress was reported overall and by type of mental health problem. Time-varying Cox proportional hazards models were developed to identify predictors of new-onset psychological distress during 2 key periods of cancer care: (1) hospital-based treatment during which women undergo treatment with breast surgery, chemotherapy, and/or radiation, and (2) 1-year transitional survivorship when women begin follow-up care. Results: The incidence of psychological distress was 16% within each period. Anxiety was present in 85.1% and 65.5% of new cases during hospital-based treatment and transitional survivorship, respectively. Predictors during both periods were younger age, receipt of axillary lymph node dissection, rheumatologic disease, and baseline menopausal symptoms, as well as new opioid dispensations, emergency department visits, and hospital contacts that occurred during follow-up. Other predictors varied based on the period of cancer care. More advanced breast cancer and type of treatment were associated with onset of psychological distress during hospital-based treatment. Psychological distress during transitional survivorship was predicted by diagnosis of localized breast disease, shorter duration of hospital-based treatment, receipt of additional hospital-based treatment in survivorship, and newly diagnosed comorbidities or symptoms. Conclusions: This study identified the predictors of new-onset psychological distress available in routinely collected administrative health databases, and showed how predictors change between hospital-based treatment and transitional survivorship periods. The results highlight the importance of developing predictive models tailored to the period of cancer care.


Assuntos
Adaptação Psicológica , Neoplasias da Mama/psicologia , Sobreviventes de Câncer/psicologia , Estresse Psicológico/diagnóstico , Sobrevivência , Demandas Administrativas em Assistência à Saúde/estatística & dados numéricos , Adulto , Idoso , Idoso de 80 Anos ou mais , Neoplasias da Mama/complicações , Neoplasias da Mama/diagnóstico , Neoplasias da Mama/terapia , Sobreviventes de Câncer/estatística & dados numéricos , Quimiorradioterapia Adjuvante/métodos , Quimiorradioterapia Adjuvante/psicologia , Estudos de Coortes , Bases de Dados Factuais/estatística & dados numéricos , Feminino , Seguimentos , Humanos , Incidência , Mastectomia/psicologia , Pessoa de Meia-Idade , Modelos Psicológicos , Prognóstico , Medição de Risco/métodos , Estresse Psicológico/epidemiologia , Estresse Psicológico/psicologia , Adulto Jovem
9.
Eur J Epidemiol ; 33(10): 897-907, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30143948

RESUMO

With greater access to regression-based methods for confounder control, the etiologic study with individual matching, analyzed by classical (calculator) methods, lost favor in recent decades. This design was costly, and the data sometimes mis-analyzed. Now, with Big Data, individual matching becomes an economical option. To many, however, conditional logistic regression, commonly used to estimate the incidence density ratio parameter, is somewhat of a black box whose output is not easily checked. An epidemiologist-statistician pair recently proposed a new estimator that is easily applied to data from individually-matched series with a 2:1 ratio (and no other confounding variables) using just a hand calculator or spreadsheet. Surprisingly-or possibly not-they overlooked classical estimators developed in earlier decades. This prompts me to re-introduce some of these, to highlight their considerable flexibility and ease of use, and to update them. Nowadays, for any matching ratio (M:1), the Maximum Likelihood result can be easily computed from data gathered under the matched design in two different ways, each using just the summary data. One is via any binomial regression program that allows offsets, applied to just M 'rows' of data. The other is by hand! The aim of this note is not to save on computation; instead, it is to make connections between classical and regression-based methods, to promote terminology that reflects the concepts and structure of the etiologic study, and to focus attention on what parameter is being estimated.


Assuntos
Modelos Estatísticos , Probabilidade , Fatores de Confusão Epidemiológicos , Humanos , Modelos Logísticos , Análise de Regressão
10.
Am J Epidemiol ; 185(6): 409-411, 2017 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-28399572

RESUMO

In previous articles in the American Journal of Epidemiology (Am J Epidemiol. 2013;177(5):431-442) and American Journal of Public Health (Am J Public Health. 2013;103(10):1895-1901), Masters et al. reported age-specific hazard ratios for the contrasts in mortality rates between obesity categories. They corrected the observed hazard ratios for selection bias caused by what they postulated was the nonrepresentativeness of the participants in the National Health Interview Study that increased with age, obesity, and ill health. However, it is possible that their regression approach to remove the alleged bias has not produced, and in general cannot produce, sensible hazard ratio estimates. First, one must consider how many nonparticipants there might have been in each category of obesity and of age at entry and how much higher the mortality rates would have to be in nonparticipants than in participants in these same categories. What plausible set of numerical values would convert the ("biased") decreasing-with-age hazard ratios seen in the data into the ("unbiased") increasing-with-age ratios that they computed? Can these values be encapsulated in (and can sensible values be recovered from) 1 additional internal variable in a regression model? Second, one must examine the age pattern of the hazard ratios that have been adjusted for selection. Without the correction, the hazard ratios are attenuated with increasing age. With it, the hazard ratios at older ages are considerably higher, but those at younger ages are well below 1. Third, one must test whether the regression approach suggested by Masters et al. would correct the nonrepresentativeness that increased with age and ill health that I introduced into real and hypothetical data sets. I found that the approach did not recover the hazard ratio patterns present in the unselected data sets: The corrections overshot the target at older ages and undershot it at lower ages.


Assuntos
Modelos de Riscos Proporcionais , Viés de Seleção , Viés , Humanos , Obesidade/epidemiologia , Inquéritos e Questionários
11.
Breast Cancer Res Treat ; 165(2): 229-245, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28553684

RESUMO

PURPOSE: Unmanaged distress has been shown to adversely affect survival and quality of life in breast cancer survivors. Fortunately, distress can be managed and even prevented with appropriate evidence-based interventions. Therefore, the objective of this systematic review was to synthesize the published literature around predictors of distress in female breast cancer survivors to help guide targeted intervention to prevent distress. METHODS: Relevant studies were located by searching MEDLINE, Embase, PsycINFO, and CINAHL databases. Significance and directionality of associations for commonly assessed candidate predictors (n ≥ 5) and predictors shown to be significant (p ≤ 0.05) by at least two studies were summarized descriptively. Predictors were evaluated based on the proportion of studies that showed a significant and positive association with the presence of distress. RESULTS: Forty-two studies met the target criteria and were included in the review. Breast cancer and treatment-related predictors were more advanced cancer at diagnosis, treatment with chemotherapy, longer primary treatment duration, more recent transition into survivorship, and breast cancer recurrence. Manageable treatment-related symptoms associated with distress included menopausal/vasomotor symptoms, pain, fatigue, and sleep disturbance. Sociodemographic characteristics that increased the risk of distress were younger age, non-Caucasian ethnicity, being unmarried, and lower socioeconomic status. Comorbidities, history of mental health problems, and perceived functioning limitations were also associated. Modifiable predictors of distress were lower physical activity, lower social support, and cigarette smoking. CONCLUSIONS: This review established a set of evidence-based predictors that can be used to help identify women at higher risk of experiencing distress following completion of primary breast cancer treatment.


Assuntos
Neoplasias da Mama/epidemiologia , Neoplasias da Mama/psicologia , Sobreviventes de Câncer , Estresse Psicológico , Feminino , Humanos , Qualidade de Vida , Fatores de Risco , Fatores Socioeconômicos
12.
Epidemiology ; 28(6): 817-826, 2017 11.
Artigo em Inglês | MEDLINE | ID: mdl-28957035

RESUMO

Panel study designs are common in environmental epidemiology, whereby repeated measurements are collected from a panel of subjects to evaluate short-term within-subject changes in response variables over time. In planning such studies, questions of how many subjects to include and how many different exposure conditions to measure are commonly asked at the design stage. In practice, these choices are constrained by budget, logistics, and participant burden and must be carefully balanced against statistical considerations of precision and power. In this article, we provide intuitive sample size formulae for the precision of regression coefficients derived from panel studies and show how they can be applied in planning such studies. We show that there are five determinants of the precision with which regression coefficients can be estimated: (1) the residual variance of the responses; (2) the variance of the slopes; (3) the number of subjects; (4) the number of measurements/subject; and (5) the within-subject range of the exposure values "X" at which the responses are measured. The planning of such studies would be greatly improved if investigators regularly reported all of the variance components in fitted random-effects models: currently, literature values for the relevant variance parameters are often not readily available and must be estimated through pilot studies or subjective estimates of "reasonable values."


Assuntos
Exposição Ambiental/estatística & dados numéricos , Modelos Estatísticos , Tamanho da Amostra , Humanos , Projetos de Pesquisa , Estatística como Assunto
13.
Am J Public Health ; 107(4): 503-505, 2017 04.
Artigo em Inglês | MEDLINE | ID: mdl-28272961

RESUMO

In previous articles in the American Journal of Epidemiology (Am J Epidemiol. 2013;177(5):431-442) and American Journal of Public Health (Am J Public Health. 2013;103(10):1895-1901), Masters et al. reported age-specific hazard ratios for the contrasts in mortality rates between obesity categories. They corrected the observed hazard ratios for selection bias caused by what they postulated was the nonrepresentativeness of the participants in the National Health Interview Study that increased with age, obesity, and ill health. However, it is possible that their regression approach to remove the alleged bias has not produced, and in general cannot produce, sensible hazard ratio estimates. First, we must consider how many nonparticipants there might have been in each category of obesity and of age at entry and how much higher the mortality rates would have to be in nonparticipants than in participants in these same categories. What plausible set of numerical values would convert the ("biased") decreasing-with-age hazard ratios seen in the data into the ("unbiased") increasing-with-age ratios that they computed? Can these values be encapsulated in (and can sensible values be recovered from) one additional internal variable in a regression model? Second, one must examine the age pattern of the hazard ratios that have been adjusted for selection. Without the correction, the hazard ratios are attenuated with increasing age. With it, the hazard ratios at older ages are considerably higher, but those at younger ages are well below one. Third, one must test whether the regression approach suggested by Masters et al. would correct the nonrepresentativeness that increased with age and ill health that I introduced into real and hypothetical data sets. I found that the approach did not recover the hazard ratio patterns present in the unselected data sets: the corrections overshot the target at older ages and undershot it at lower ages.


Assuntos
Modelos de Riscos Proporcionais , Viés de Seleção , Viés , Humanos , Obesidade/epidemiologia , Inquéritos e Questionários
14.
Biometrics ; 71(1): 42-52, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25223544

RESUMO

Pooling of controls under nested-case control settings can produce substantial efficiency gains compared to standard time-matched analysis using the Mantel-Haenszel method or conditional logistic regression. In the context of possible adverse effects of early childhood vaccinations, we propose pooling of the information from the controls to estimate the population exposure prevalence as a parametric or nonparametric function of time, and possibly other factors. This function in turn may be used as a plug-in estimate to control for confounding in the subsequent estimation of rate ratios. We derive standard errors for the resulting two-step estimators, demonstrate through simulations the efficiency gains compared to standard matched analysis, and propose a novel graphical presentation of the vaccination and adverse event time data. We formulate the methods in the general framework of case-base sampling, which subsumes the different case-control and case-only methods.


Assuntos
Estudos de Casos e Controles , Efeitos Colaterais e Reações Adversas Relacionados a Medicamentos/epidemiologia , Modelos Estatísticos , Vacinação/estatística & dados numéricos , Viroses/epidemiologia , Viroses/prevenção & controle , Simulação por Computador , Interpretação Estatística de Dados , Métodos Epidemiológicos , Humanos , Incidência , Medição de Risco/métodos
15.
BJU Int ; 114(6b): E99-E104, 2014 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-24684511

RESUMO

OBJECTIVE: To evaluate the clinical and pathological factors influencing the risk of disease progression in a cohort of patients with low-intermediate risk prostate cancer under active surveillance (AS). PATIENTS AND METHODS: We studied 300 patients diagnosed between 1992 and 2012 with prostate adenocarcinoma with favourable parameters or who refused treatment and were managed with AS. Of those, 155 patients with at least one repeat biopsy and no progression criteria at the time of the diagnosis were included for statistical analyses. Patients were followed every 3-6 months for prostate-specific antigen (PSA) measurement and physical examination. Patients were offered repeat prostatic biopsy every year. Disease progression was defined as the presence of one or more of the following criteria: ≥ 3 positive cores, >50% of cancer in at least one core, and a predominant Gleason pattern of 4. RESULTS: For the 155 patients, the mean (sd) age at diagnosis was 67(7) years; the median (interquartile range) follow-up was 5.4(3.6-9.5) years. Of these, 67, 25, six, and two patients had two, three, four, and five repeat biopsies, respectively. At baseline, 11 (7%) patients had a Gleason score of 3+4, while the remaining 144 (93%) patients had a Gleason score of ≤ 6. In all, 50 (32.3%) patients had disease progression on repeat biopsies, with a median progression-free survival time of 7 years. The rate of disease progression decreased after the second repeat biopsy. The 5-year overall survival rate was 100%. Having a PSA density (PSAD) of >0.15 ng/mL/mL, >1 positive core, and Gleason score >6 at the time of the diagnosis was associated with a significantly higher rate of disease progression on univariate analysis (P < 0.05), while a maximum percentage of cancer in any core of >10% showed a trend toward significance for a higher progression rate (P = 0.054). On multivariate analysis, only the presence of a PSAD of >0.15 ng/mL/mL remained significant for a higher progression rate (P < 0.05). Of the 155 patients, five (3.2%) subsequently received radiotherapy, 13 (8.4%) received hormonal therapy, and 13 (8.4%) underwent radical prostatectomy. CONCLUSION: AS is a suitable management option for patients with clinically low-risk prostate cancer. A PSAD of >0.15 ng/mL/mL is an important predictor for disease progression.


Assuntos
Adenocarcinoma/patologia , Neoplasias da Próstata/patologia , Conduta Expectante , Adenocarcinoma/sangue , Adenocarcinoma/mortalidade , Idoso , Progressão da Doença , Intervalo Livre de Doença , Aspiração por Agulha Fina Guiada por Ultrassom Endoscópico , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Gradação de Tumores , Antígeno Prostático Específico/sangue , Neoplasias da Próstata/sangue , Neoplasias da Próstata/mortalidade , Fatores de Risco , Taxa de Sobrevida
16.
17.
J Med Screen ; : 9691413231215963, 2023 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-37990538

RESUMO

INTRODUCTION: Screening trials and meta-analyses emphasize the ratio of cancer death rates in screening and control arms. However, this measure is diluted by the inclusion of deaths from cancers that only became detectable after the end of active screening. METHODS: We review traditional analysis of cancer screening trials and show that ratio estimates are inevitably biased to the null, because follow-up (FU) must continue beyond the end of the screening period and thus includes cases only becoming detectable after screening ends. But because such cases are expected to occur in equal numbers in the two arms, calculation of the difference between the number of cancer deaths in the screening and control arms avoids this dilutional bias. This difference can be set against the number of invitations to screening; we illustrate by reanalyzing data from all trials of tomography screening of lung cancer (LC) using this measure. RESULTS: In nine trials of LC screening from 2000 to 2013, a total of 94,441 high-risk patients were invited to be in screening or control groups, with high participation rates (average 95%). In the older trials comparing computed tomography to chest X-ray, 88,285 invitations averted 83 deaths (1068 per death averted (DA)). In the six more recent trials with no screening in the control group, 69,976 invitations averted 121 deaths (577 invitations per DA). DISCUSSION: Screens per DA is an undiluted measure of screening's effect and it is unperturbed by the arbitrary duration of FU. This estimate can be useful for program planning and informed consent.

19.
Epidemiol Rev ; 33: 36-45, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-21624962

RESUMO

Randomized trials involving large numbers of people and long follow-up have helped measure the mortality reductions achievable by screening for cancer. However, in many of these trials, the reported reductions have been modest. Part of the reason is the inappropriate way the reductions have been calculated. Analyses have largely ignored the fact that there is a time window in the first several years after screening begins in which there cannot be a sizable mortality reduction, followed by one in which the reductions become evident, and-unless screening is continued-a third window in which mortality rates in the screened group revert to those in the unscreened group. This review uses time-specific mortality ratios to address the timing and extent of the reductions achieved in trials of screening for prostate, breast, and colorectal cancer. The author finds that the mortality reductions reported in the literature have substantially underestimated what might be accomplished with continued screening. The natural history of the disease, the frequency of screening, and the duration of follow-up determine the time patterns in the reductions observed in trials. Without appropriate analyses, results from cancer screening trials will be distorted.


Assuntos
Ensaios Clínicos como Assunto/normas , Programas de Rastreamento/mortalidade , Neoplasias/mortalidade , Ensaios Clínicos como Assunto/métodos , Neoplasias Colorretais/diagnóstico , Neoplasias Colorretais/mortalidade , Neoplasias Colorretais/prevenção & controle , Diagnóstico Precoce , Humanos , Masculino , Neoplasias/diagnóstico , Neoplasias/prevenção & controle , Neoplasias da Próstata/diagnóstico , Neoplasias da Próstata/mortalidade , Neoplasias da Próstata/prevenção & controle
20.
J Antimicrob Chemother ; 66(2): 424-33, 2011 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21172784

RESUMO

BACKGROUND: Resistance to antibacterial drugs can be contained by judicious prescribing. In particular, the use of these drugs in children requires ongoing surveillance. While there was a decline in antibacterial prescribing in the UK during the 1990s, recent trends are less well known. OBJECTIVES: To describe antibiotic prescribing patterns and time trends in children in the UK over the last two decades. METHODS: We identified all children ages 0-19 years from 1993 to 2007 and their antibiotic prescriptions from the General Practice Research Database. We used Poisson regression to estimate prescription rates considering the children's age and gender, calendar year and practice. RESULTS: The cohort included 1 751 645 children with 5 835 891 antibacterial prescriptions. The average prescription rate was 511 prescriptions per 1000 person-years [95% confidence interval (CI) 509-513]. As of 1995, the rate decreased to 419/1000 person-years (95% CI 411-426) in 2000, then increased to 568/1000 person-years (95% CI 559-577) in 2007. Between 2000 and 2007, rates increased on average by 4.3% (95% CI 3.7-5.0%) annually, amounting to an increase of 40.7% (95% CI 34.5-47.2%) for all children. Rates were generally higher in girls, except for boys <5 years. Broad-spectrum penicillins were most frequently prescribed; their rate increased on average by 4.6% annually (95% CI 4.0-5.3%) after 2000. This trend was similar in most classes of antibacterials. CONCLUSIONS: Antibacterial prescribing to outpatient children in the UK has been steadily increasing since 2000, consistently for boys and girls, across all ages and antibacterial classes.


Assuntos
Antibacterianos/uso terapêutico , Penicilinas/uso terapêutico , Padrões de Prática Médica/tendências , Atenção Primária à Saúde/tendências , Adolescente , Criança , Pré-Escolar , Farmacorresistência Bacteriana , Uso de Medicamentos/tendências , Feminino , Humanos , Lactente , Recém-Nascido , Masculino , Pediatria/tendências , Reino Unido
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