应用广义估计方程评估儿童肥胖综合干预效果

目的 评估儿童肥胖综合干预项目在控制儿童超重/肥胖及改善儿童肥胖相关知识-态度-行为的效果, 为制定儿童肥胖干预措施提供依据。方法 通过整群随机对照实验设计并采用广义估计方程模型对儿童肥胖相关重复测量数据进行统计分析。结果 实验组965 人, 对照组895 人。实验组的学生从正常体重发展为超重/肥胖的风险是对照组学生的0.824 倍, 即干预措施降低了17.6%成为超重/肥胖的风险（P＝0.031）。此外, 实验组学生肥胖相关知识正确率的均值提高一个单位的可能性是对照组学生的1.044 倍（P＝0.001）;实验组学生肥胖相关正确态度率的均值提高一个单位的可能性是对照组学生的1.023 倍（P＝0.001）;实验组学生肥胖相关行为的均值提高一个单位的可能性是对照组学生的1.522 倍（P＝0.046）。结论 基于知识-态度-行为模式建立的针对儿童肥胖的干预措施可有效降低正常体重儿童发展为超重/肥胖的风险, 并在改善儿童肥胖相关知识-态度-行为方面呈现一定的效果。     

应用广义估计方程评估"农村义务教育学生营养改善计划"地区营养宣教实施效果

目的运用广义估计方程(generalized estimating equation,GEE)评价湖北省"农村义务教育学生营养改善计划"(简称"计划")地区营养宣教干预效果,为在"计划"地区大规模开展营养宣教提供理论和实践依据。方法采取随机整群抽样法在湖北省恩施市"计划"地区4所中小学分别设立对照组和干预组。干预前对所有选择对象进行问卷调查;干预组营养宣教干预5个月后,对两组学生进行第2次调查。采用GEE分析结果得出统计学结论。结果干预组233人,对照组209人。控制其他协变量,干预组干预后营养知识、日常健康饮食行为相对于基线分别提高了0.82分(χ~2=24.31,P0.001)、3.29分(χ~2=14.07,P0.001);干预组干预后日常不良饮食行为(χ~2=0.12,P=0.773)、"计划"营养餐满意度及依从性(χ~2=2.44,P=0.118)得分改变相对于基线均无显著性。结论营养宣教能显著性提高"计划"地区中小学生营养知识知晓率并促进日常健康饮食行为水平,但未能有效改善其日常不良饮食行为、"计划"营养餐满意度和依从性水平。GEE方法处理营养干预纵向资料具有极大的实用性和灵活性。     

捕获再捕获法估计吸毒人群基数的数据模型研究

目的建立捕获-再捕获法估计吸毒人群基数的分析数据模型.方法收集和分析戒毒所登记资料,确定捕获期和捕获间隔期,建立捕获-再捕获法使用的分析数据模型,以估计当地吸毒人群基数.结果获得建立捕获-再捕获法使用的分析数据模型的方法.结论按照统一的方法建立数据分析模型是运用捕获-再捕获法对吸毒人群基数进行估计的关键.     

Estimating the Prevalence of Injection Drug Users in the U.S. and in Large U.S. Metropolitan Areas from 1992 to 2002

This paper estimates the prevalence of current injection drug users (IDUs) in 96 large U.S. metropolitan statistical areas (MSAs) annually from 1992 to 2002. Multiplier/allocation methods were used to estimate the prevalence of injectors because confidentiality restrictions precluded the use of other commonly used estimation methods, such as capture-recapture. We first estimated the number of IDUs in the U.S. each year from 1992 to 2002 and then apportioned these estimates to MSAs using multiplier methods. Four different types of data indicating drug injection were used to allocate national annual totals to MSAs, creating four distinct series of estimates of the number of injectors in each MSA. Each series was smoothed over time; and the mean value of the four component estimates was taken as the best estimate of IDUs for that MSA and year (with the range of component estimates indicating the degree of uncertainty in the estimates). Annual cross-sectional correlations of the MSA-level IDU estimates with measures of unemployment, hepatitis C mortality prevalence, and poisoning mortality prevalence were used to validate our estimates. MSA-level IDU estimates correlated moderately well with validators, demonstrating adequate convergence validity. Overall, the number of IDUs per 10,000 persons aged 15-64 years varied from 30 to 348 across MSAs (mean 126.9, standard deviation 65.3, median 106.6, interquartile range 78-162) in 1992 and from 37 to 336 across MSAs (mean 110.6, standard deviation 57.7, median 96.1, interquartile range 67-134) in 2002. A multilevel model showed that overall, across the 96 MSAs, the number of injectors declined each year until 2000, after which the IDU prevalence began to increase. Despite the variation in component estimates and methodological and component data set limitations, these local IDU prevalence estimates may be used to assess: (1) predictors of change in IDU prevalence; (2) differing IDU trends between localities; (3) the adequacy of service delivery to IDUs; and (4) infectious disease dynamics among IDUs across time.     

A physiologically based pharmacokinetic/pharmacodynamic model for carbofuran in Sprague-Dawley rats using the exposure-related dose estimating model.

Carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl-N-methylcarbamate), a broad spectrum N-methyl carbamate insecticide, and its metabolite, 3-hydroxycarbofuran, exert their toxicity by reversibly inhibiting acetylcholinesterase (AChE). To characterize AChE inhibition from carbofuran exposure, a physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) model was developed in the Exposure-Related Dose Estimating Model (ERDEM) platform for the Sprague-Dawley (SD) rat. Experimental estimates of physiological, biochemical, and physicochemical model parameters were obtained or based on data from the open literature. The PBPK/PD model structure included carbofuran metabolism in the liver to 16 known metabolites, enterohepatic circulation of glucuronic acid conjugates, and excretion in urine and feces. Bolus doses by ingestion of 50 microg/kg and 0.5 mg/kg carbofuran were simulated for the blood and brain AChE activity. The carbofuran ERDEM simulated a half-life of 5.2 h for urinary clearance, and the experimental AChE activity data were reproduced for the blood and brain. Thirty model parameters were found influential to the model outputs and were chosen for perturbation in Monte Carlo simulations to evaluate the impact of their variability on the model predictions. Results of the simulation runs indicated that the minimum AChE activity in the blood ranged from 29.3 to 79.0% (as 5th and 95th percentiles) of the control level with a mean of 55.9% (standard deviation = 15.1%) compared to an experimental value of 63%. The constructed PBPK/PD model for carbofuran in the SD rat provides a foundation for extrapolating to a human model that can be used for future risk assessment.     

Investigation of validity of model for estimating shear force applied to buttocks in elderly people with kyphosis while sitting comfortably on a chair

Purpose.?The purpose of the present study was to investigate the validity of a model for estimating shear force on the buttocks of elderly people with kyphosis.

Method.?The subjects with kyphosis were 10 elderly people in a facility providing health care services for the elderly. The shear force was measured using a force plate and, simultaneously, the position of the resultant centre of mass of the upper body and the inclination angle of the trunk were measured. The estimated shear force was calculated by substituting these values in the model.

Results.?The average value of the measured shear force was 8.4 SD 1.4 [%BW], and the average value of the estimated shear force was 5.8 SD 1.0 [%BW]. Although there was a significant difference between these two values (p?<?0.01), there was a strong positive correlation between them (r?=?0.786, p?<?0.01). The regression line between the two values was y?=?1.097x + 1.96, where x?=?estimated value, y?=?measured value.

Conclusions.?These results suggest that the estimated shear force was close to the measured shear force and thus is approximately known by substituting the calculated values for the linear regression.     

Assessment of Relative Improvement Due to Weights Within Generalized Estimating Equations Framework for Incomplete Clinical Trials Data

Abstract

The generalized estimating equations (GEE) approach has been popular for analyzing longitudinal clinical trials data with missing values. The GEE methodology allows one to obtain unbiased estimates only when the data are missing completely at random. The use of weights into the estimating equations has been proposed as an adjustment for differential probabilities of nonresponse to accomodate more realistic missingness mechanisms. This article addresses the problem of assessing the relative improvement due to weights using simulated data generated around an alcoholic hepatitis trial. We argue that weights yield improved results in terms of bias, coverage rate, and efficiency only when the underlying missingness mechanism is correctly specified.     

脑-机接口中神经元放电信号的解码算法

基于神经元放电信号的脑-机接口(BCI)的核心问题是获得神经元锋电位的放电率,然后利用神经元群体解码算法解码运动轨迹。综述了当前及经典的放电率估计方法的理论依据,并对各种算法的优缺点进行了比较;同时介绍了BCI中利用放电率解码运动轨迹的主要算法：群矢量算法、线性滤波及卡尔曼滤波;最后介绍了将放电率估计算法应用于BCI中...