摘要：流行病学是对一定数量的人群进行特征描述和比较,并在此基础上进行因果推断。研究人群的形成是其第一步。本研究以观察性研究为例,首先定义个体截面和人群截面,并阐明其测量需满足的3个假设:属性真实值随时间保持不变,属性变量间互不干扰,个体间互不干扰;接着指出因果推断研究应以待定因(或暴露)的发生或状态开始的时间为标准进行统一;最后,基于人群截面的双重角色,提出人群的因果推断研究可分为2类:历史重建研究和探索未来研究,并初步梳理了研究设计框架、估计的效应及设计间的关系。从因果思维角度探讨研究人群的形成过程,可为明确因果推断研究设计类型奠定基础,选取合适的效应估计进行因果推断,值得深入研究。

摘要：动脉粥样硬化性肾动脉狭窄的血管成形治疗(包括球囊成形术、支架置人和外科成形术)获得广泛关注,但这些技术与其它方法或与标准的药物治疗的前瞻性随机对照试验(RCT)很少.为使这种技术标准化和解答血管成形规范应用的有关问题,需要设计严谨、严格控制的目标明确、样本设计和完成的数量足够大,结果经得起进一步评估的试验,作者编译了美国医学会(AHA)肾动脉血管成形的临床试验指南,以使国内同行初步了解肾动脉血管成形的RCT试验的设计、执行、评价和报告,并能对这一重要领域的研究人员提供帮助.

摘要：随着我国经济建设与卫生事业的发展,人民的平均期望寿命亦大大延长,疾病谱也随之发生改变,慢性病已成为当前威胁人们的健康与生命的主要问题之一。慢性病由于常是多种致病因子协同作用引起,潜伏期长,缺乏明确的暴露日期与发病的具体时间等情况,对病因研究带来一定困难。流行病学是从群体角度,在现场(社区)进行病因研究为慢性病的病因研究与防制作出自己的贡献。流行病学是研究人群中疾病的频率与决定因素来探索病因的。

摘要：Objective: To examine temporal trends in the rates of severe bronchopulmonary dysplasia (BPD) between 1994 and 2002. Study design: In a retrospective cohort study, all infants with a gestational age (GA) < 33 weeks in a large managed car e organization were identified. Annual rates of BPD (defined as an oxygen requir ement at 36 weeks corrected GA), severe BPD (defined as respiratory support at 3 6 weeks corrected GA), and death before 36 weeks corrected GA were examined. Res ults: Of the 5115 infants in the study cohort, 603 (12% ) had BPD, including 24 6 (4.9% ) who had severe BPD. There were 481 (9.5% ) deaths before 36 weeks co rrected GA. Although the decline in BPD in this period was not significant, the rates of severe BPD declined from 9.7% in 1994 to 3.7% in 2002. Controlling for gestational age, the odds ratio (95% CI) for annual rate of decline in severe BPD was 0.890 (0.841- 0.941). Controlling for gestational ag e, deaths before 36 weeks corrected GA also declined, with the odds ratio (CI) f or the annual decline being 0.944 (0.896- 0.996). Conclusions: In this study po pulation, the odds of having of BPD remained constant after controlling for GA. However, the odds of having severe BPD declined on average 11% per year betwee n 1994 and 2002.

摘要：Objective: The purpose of this study was to assess the association between previous maternal Toxoplasma gondii (T gondii) infection and risk of fetal death. Study design: This was a population-based prospective cohort of 29,912 pregnant women without acute T gondii infection in Norway. Results: In the study population, 2937 (9.8% ) women had evidence of previous maternal T gondii infection, and 299 (1.0% ) had fetal deaths. We found no association between previous T gondii infection and risk of fetal death at ≥ 20 weeks of gestation. We did find a trend for an increased risk of fetal death at ≥ 16 and < 20 weeks of gestation. However, we noted no association between previous T gondii infection and risk of fetal death at all birth weight categories (≥ 1000, ≥ 500 and <1000, and < 500 g). Conclusion: These data do not indicate an increased risk of fetal death at ≥ 20 weeks of gestation in women with previous maternal T gondii infection.

摘要：近年来HLA等位基因与HBV相关性研究,相继有所报道[1],但因被研究人群种族、检测方法、实验设计方面的差异,研究结论也有所不同,因而HLA与乙型肝炎的相关性,目前尚无定论.我们随机选取HBV感染后不同临床类型患者,采用序列特异性引物-多聚酶链式反应(SSP-PCR)方法,进行了HLA-Ⅰ,Ⅱ类基因与HBV感染预后相关性研究,现将结果报道如下。

摘要：目的：最近发现升高或降低的血压与主体的活动有关,这也代表一个方便的预防工具。然而,客观的纵向的研究数据对于提供量身定制的建议是必要的。本研究的目的是基于连接设备大样本用户,来评估步行和血压之间关系。设计和方法：应用横截面研究和纵向多元线性回归,分析了来自19000例携带Withings脉冲活动追踪器和无线血压计的成年人数据。

摘要：Background: Dead Sea (DS) salt solution soaks are used in combination with narrowband ultraviolet B (NB- UVB) to treat psoriasis in many centres, particularly in continental Europe. No previously published controlled study has assessed DS salt + NB- UVB balneophototherapy. Objectives: To compareDS salt balneophototherapy with NB- UVB monotherapy for chronic plaque psoriasis. Methods: Sixty patients with chronic plaque psoriasis participated in this paired, controlled study, with pretreatment DS salt soaks randomly allocated to each participant’ s right or left study limb. Psoriasis severity was assessed with a Scaling, Erythema and Induration score by a blinded observer. Assessments were weekly during the therapy course, and thereafter 8- weekly until relapse or for up to 1 year after clearance. Results: The mean area under the psoriasis severity- time curves during treatment was not detectably lower with DS salt balneophototherapy than with NB- UVB monotherapy (P=0.099). The psoriasis severity score fell slightly more from beginning to end of courses with DS salt balneophototherapy than with NB- UVB monotherapy (P=0.019). There was no detectable difference in times to relapse. Conclusions: In this population the addition of pretreatment DS salt soaks to NB- UVB did not result in a clinically important improvement in clearance of psoriasis.