山西省某既往有偿献血地区人免疫缺陷病毒感染的横断面研究

目的了解山西省某既往有偿献血地区人免疫缺陷病毒（HIV）感染率,并探索HIV感染的危险因素。方法选择山西省某县4个村所有18～64岁村民开展以社区为基础的横断面研究,采用标准化问卷收集研究对象的人口学、医疗史、危险行为等信息,采集静脉血用于检测HIV抗体。基于广义估计方程的logistic回归模型被用于分析HIV感染的危险因素。人群归因分值被用于测量危险因素在当地HIV感染发生中的公共卫生学意义。结果4个村中82．5％（3062／3711）的18～64岁村民参加本次调查,共发现40例HIV感染者,该地区HIV总的感染率为1．3％（40／3062）,献血人群和非献血人群HIV感染率分别为4．1％（37／904）和0．1％（3／2158）。多因素分析发现,献全血（调整OR=13．25,95％CI：3．02～58．25）和献血浆（调整OR=87．85,95％CI：22．22～347．27）与该地村民感染HIV有关,二者累计的人群归因分值（PAF）为89．8％。03号村村民感染HIV的危险性高于04号村村民（调整OR=12．26,95％CI：1．46～103．00）。结论该地区HIV感染流行水平相对较低,引起村民HIV感染流行的主要因素是既往有偿献血（浆）,未出现HIV从献血人群向非献血人群的明显蔓延。     

IL-10基因多态性与江苏地区高危人群丙型肝炎病毒感染转归的关联研究

目的 探讨江苏地区高危人群IL-10基因多态性与丙型肝炎病毒(HCV)感染转归的关系.方法 运用Taqman-MGB技术检测264例HCV自限感染者、371例HCV持续感染者和920例对照者的IL-10-819T/C、-592A/C、- 1082A/G位点基因多态性.结果 调整性别、年龄和高危人群种类混杂因素后,logistic回归分析显示3个位点的基因多态性分别与HCV感染转归无显著关联(P值均＞0.05).进一步分层分析显示,-819T/C位点中,TC基因型使中年人、女性和有偿献血人群HCV自限感染的机会增加[调整OR值及其95％CI分别为2.160( 1.163 ～ 4.011)、1.693( 1.066～ 2.688)和4.084( 1.743～9.570)],在有偿献血人群中使个体进展为持续感染的风险降低(调整OR=0.312,95％CI:0.130 ～ 0.747);CC基因型使血液透析人群HCV自限感染的机会增加(调整OR=2.120,95％CI:1071～4.197),同时在有偿献血人群中使个体进展为持续感染的风险降低(调整OR=0.156,95％CI:0.043 ～ 0.566).-592A/C位点中,AC基因型使中年人、女性和有偿献血人群HCV自限感染的机会显著增加[调整OR值及其95％CI分别为2.176(1.173 ～4.037)、1.659( 1.055 ～ 2.607)和3.704( 1.625 ～ 8.443)],在女性中增加了HCV持续感染的风险(调整OR=1.525,95％CI:1.017～ 2.286),在吸毒人群中使个体进展为持续感染的风险增加(调整OR=1.845和95％CI:1.122～3.034),而在有偿献血人群中使个体进展为持续感染的风险降低(调整OR=0.361,95％CI:0.155 ～ 0.841).CC基因型增加了有偿献血人群HCV自限感染的机会,同时也使个体进展为持续感染的风险降低[调整OR值及其95％CI分别为3.125(1.016 ～ 9.605)和0.218( 0.063～0.748)].-1082A/G位点中,突变基因型AG/GG能增加有偿献血人群HCV自限感染的机会(调整OR=3.780,95％CI:1.620 ～ 8.82 0).结论 IL-10-819T/C、-592A/C、-1082A/G三个位点的基因多态性在不同高危人群中与HCV感染转归可能有一定关联.     

有偿献血者HIV-1、HCV、HBV合并感染调查

目的调查山西省农村某既往有偿献血地区人类免疫缺陷病毒（HIV）、丙型肝炎病毒（HCV）和乙型肝炎病毒（HBV）合并感染状况。方法对4个村年龄18～59岁的村民进行问卷调查和血样采集，检测项目包括HIV-1抗体、HCV抗体和HBV表面抗原（HBsAg）。结果人群HIV、HCV、HBV感染率分别为1．3％（40／3062），12．7％（389／3062），3．5％（103／2982）；40名HIV感染者中，85．0％伴HCV感染，2．5％伴HBV感染。多因素Logistic回归分析提示，既往有偿献血（浆）史是HIV、HCV及HIV／HCV合并感染的危险因素，而与HBsAg阳性呈负相关，过去5年外出打工史与HIV、HBsAg、HIV／HCV感染差异有统计学意义；未发现吸毒、终生性伴数、婚外性行为、商业性行为和各种性行为中安全套的使用与HIV、HCV、HBV感染及合并感染有关联。结论应重点关注HIV、HCV和HBV感染者的治疗、健康教育和行为干预。     

河南信阳农村献血人员HIV、HCV、HBV感染情况分析

目的了解信阳市献血浆人群HIV、HCV、HBV感染率及其流行因素。方法对信阳市某县9个乡有偿献血浆人群聚集地村民进行HIV、HCV、HBV感染的流行病学调查。结果调查村民987人，发现HIV、HCV、HBV感染率分别为5．57％、26．14％、13．07％。其中有偿献血员604人，HIV、HCV感染率分别为8．94％、40．89％，显著高于非献血员的HIV、HCV感染率。结论豫南局部地区有偿献血浆人群中HIV、HCV感染率较高，在HIV阳性有偿献血浆人群中，HCV感染率很高，而HBV感染率则无此种现象。     

血站类型和献血方式对献血员感染HIV的影响

目的 研究血站经营类型和献血方式等因素对有偿献血员感染HIV的影响。方法 根据WHO／UN-AIDS推荐的HIV检测策略Ⅱ，从2002年10月至2003年3月对中国中部某贫困县行政村全部有偿献血员进行HIV筛查和问卷调查。结果 参加筛查的有偿献血员共462人，其中HIV筛查抗体阳性91人，阳性率为19．70％(95％CI16．17％～23．62％)；献血员曾献过血的血站总共75家，献全血和单采血浆次数在个体经营、本县、外县、地区以及部队经营血站间有显著性差异；单因素分析显示，在各种类型血站只献全血的献血员HIV阳性率为0，去个体私营血站献血浆感染HIV的风险显著高于本县血站，本县血站显著高于外县血站；多因素Logistic分析显示，只有到个体私营血站和本县血站献血浆是感染艾滋病病毒的危险因素，调整OR值分别为2．72(95％C11．95～3．79)和1．12(95％C11．06-1．18)；曾经到个体经营血站和本县血站的有偿献血员HIV筛查阳性率分别为72．73％和20．66％。结论 该村有偿献血员感染HIV的主要原因是去个体经营血站和本县血站献血浆；卫生部门应确定“问题血站”并根据献血员在其献血情况来估计感染人数和确定重点干预地区。     

某县注射吸毒人群HIV感染率和危险因素研究

目的 评估某县注射吸毒人群HIV感染率，探讨HIV感染相关的危险因素。方法 在某县戒毒所和社区征集满足条件的吸毒者，由经统一培训的调查员在单独的房间内进行访谈，同时采集血样进行HIV抗体检测。结果 调查注射吸毒人群269人，HIV感染率为26．0％（70／269）。在多因素非条件Logistic回归模型中，注射吸毒人群HIV感染有统计学意义。危险因素包括家庭所在地为县城（相对于其他乡镇）（OR=4．08，95％CI：1．65～10．08）、注射总次数≥1000次组（OR=7．45，95％CI：2．62～21．16）或注射总次数100～999次（OR=3．03，95％CI：1．04～8．86），在戒毒所内有共用针具行为（OR=8．32，95％CI：2．77～24．98）或仅有戒毒所外共用针具行为（OR=5．54，95％CI：1．97～15．60）。结论 目前该县注射吸毒人群HIV流行处于较高水平，需加强共用针具危险性的宣传教育，加强打击毒品隐蔽进入戒毒所的力度。     

云南省某市锡矿工人性病与艾滋病的流行病学调查

目的 估计云南省某市矿区锡矿工人性病、艾滋病感染状况及相关知识,并分析可能的危险因素。方法 2006年3-6月在云南省某市的5个矿区开展以矿区为基础的横断面研究,共纳入1796名矿工。采用标准化问卷匿名收集研究对象的性病与艾滋病知识、性行为等信息,并采集7ml静脉血和15ml尿检测4种性病和艾滋病感染情况。结果 调查矿工中共检出12例人类免疫缺陷病毒（human immunodeficiency virus,HIV）抗体阳性者,阳性率为0．7％（12／1760）,其他性病阳性率分别为梅毒1．8％（31／1760）,2型单纯疱疹（herpes simplex virustype-2,HSV-2）9．6％（169／1760）,淋球菌0．8％（14／1773）,沙眼衣原体4．8％（85／1773）,除HIV外的其他性病总患病率为14．9％（264／1776）。HIV感染和吸毒（调整OR=17．8;95％CI：4．0—78．8）、12个月内嫖娼次数（调整OR=8．7,95％CI：1．9—39．0）、文身（调整OR=6．6;95％CI：1．8—24．0）、手术（调整OR：6．0;95％CI：1．6—22．5）、共用牙刷（调整OR=5．6;95％CI：1．0—31．3）等因素的联系有统计学意义。性病感染和民族（调整OR=2．0;95％CI：1．5—2．7）、年龄（调整OR=1．7;95％CI．1．0—2．9）、吸毒（调整OR=2．3;95％CI：1．0～5．2）、和配偶住一起（调整OR=1．4;95％CI：1．1—1．9）及嫖娼（调整OR=1．9;95％CI：1．4—2．6）等因素的联系有统计学意义。艾滋病相关知识全部回答正确率为4．1％（49／1201）,有性经历的矿工中自我报告嫖娼的比例为21．6％（339／1569）。结论 该地区矿工性病、艾滋病感染率较高,性病、艾滋病知识匮乏,不安全性行为比较普遍,安全套使用率低,自我保护意识差,存在多种性病、艾滋病的传播途径,应加强该人群教育干预工作。     

我国不同地区吸毒人群梅毒感染状况分析

目的了解我国不同地区吸毒者梅毒感染状况,为艾滋病、性病综合防治提供依据。方法采取简单抽样或滚雪球法,在广西南宁、新疆喀什和广东东莞抽取995名吸毒者进行问卷调查并抽血,收集人口学及性行为特征,采用快速血浆反应素试验法检测梅毒抗体。结果广西南宁、新疆喀什和广东东莞吸毒者的梅毒感染率分别为17．5％、10．4％和9．6％。Logistic回归分析结果显示广西南宁吸毒者梅毒感染的主要危险因素为女性（OR8．50;95％CI：2．51～28．78;P=0．001）;新疆喀什吸毒者梅毒感染的主要危险因素为女性（OR7．44;95％CI：1．40～39．57;P〈0．05）、有配偶（OR2．51;95％CI：1．05～6．00;P〈0．05）、低教育程度（OR3．06;95％CI：1．12～8．39;P〈0．05）;广东东莞吸毒者梅毒感染的主要危险因素为女性（OR4．52;95％CI：1．81～11．28;P=0．001）、有配偶（OR3．96;95％CJ：1．71～9．17;P=0．001）、低收入（OR3．12;95％CI：1．41～6．89;P〈0．01）、注射吸毒（OR2．81;95％CI：1．09～7．24;P〈0．05）。结论目前我国艾滋病传播以性传播为主,吸毒人群高危性行为是艾滋病由高危人群向一般人群传播的重要途径。因此,对高危人群实施预防干预措施应具有针对性。     

慢性阻塞性肺疾病危险因素病例对照研究

目的探讨慢性阻塞性肺疾病（COPD）发病的相关危险因素，为开展COPD的一级预防提供依据。方法采用按年龄±3岁进行1：1配比的病例一对照研究方法，对435例来源于2003年1月-2006年4月某市级医院的COPD患者及其对照者应用条件Logistic回归进行危险因素分析。结果单因素分析结果显示，性别（OR=1．802，95％CI：1．385--2．346）、药物过敏史（OR=4．346，95％CI：2．838～6．657）、吸烟（OR=2．857，95％CI：2．145～3．807）、吸烟年限〉10a（OR=2．719。95％CI：2．041～3．621）、日吸烟量〉10支（OR=2．250，95％CI：1．601～3．161）、开始吸烟年龄≤20岁（0R=1．909，95％CI：1．140。3．198）、吸烟指数大于300年支（OR=2．241，95％CI：1．645-3．054）和高血糖（OR=2．469，95％CI：1．772～3．441）为COPD的危险因素。多因素分析结果显示，性别（OR=1．595，95％CI：1．124～2．264）、药物过敏史（OR=4．029，95％（CI：2．411～6．735）、吸烟（OR：2．635，95％CI：1．844～3．764）和高血糖（OR=2．390，95％CI：1．632-3．502）为COPD的危险因素。结论男性、药物过敏史、吸烟和高血糖为COPD的主要危险因素。     

北京和南京两地代谢综合征危险因素分析

目的分析北京和南京两地人群代谢综合征的危险因素。方法采用整群抽样对北京和南京的6123人进行流行病学调查,应用IDF（2005）定义。采用多因素Logistic回归分析可能存在的危险因素。结果男性和女性的年龄标化患病率分别为19．5％和33．6％。多因素条件Logis—tic回归结果,女性（OR=1．49;95％CI（1．40,1．59））、年龄增长（OR=1．23;95％CI（1．16,1．31））、低体力活动（OR=1．76;95％a（1．13,2．76））、糖尿病家族史（OR：1．33;95％CI（1．11,1．60））、高血压家族史（OR=1．46;95％CI（1．29,1．65））、年龄性别交互作用（OR=1．29;95％a（1．21,1．40））、居住在城市（OR=1．09;95％CI（1．02,1．18））均是代谢综合征的危险因素。居住在南京（OR=0．76;95％CI（0．71,0．81））是代谢综合征的保护因素。结论代谢综合征是多重危险因素共同作用的结果,其中女性、慢病家族史、低体力活动是其重要的危险因素。     

Risk Factors for Hepatitis C Virus Infection among Blood Donors in Georgia

BACKGROUND: Growing awareness about the importance of blood safety for controlling the transmission of hepatitis C virus (HCV) has helped to decrease the spread of this virus in many settings. This study was conducted in order to evaluate potential risk factors for HCV infection among blood donors in Georgia. METHODS: The study population consisted of 553 blood donors in three major Georgian cities: Tbilisi, the capital city and Batumi and Poti, naval port cities. Risk factors were examined using a behavior questionnaire. All blood samples were initially tested using 3rd generation anti-HCV enzyme-linked immunosorbent assays and confirmed using recombinant immunoblot assays and nucleic acid testing. RESULTS: Forty-three blood donors, 7.8%, were confirmed HCV positive. Significant risk factors included: drug injection ever (OR: 42; 95% CI: 3.2-550.7); history of hepatitis (OR: 25.9; 95% CI: 4.6-145.5); history of a previous surgical procedure (OR: 148.4; 95% CI: 26.9-817.4); blood transfusion (OR: 25.9; 95% CI: 3.2-210.9). CONCLUSIONS: This study found a very high prevalence of HCV among blood donors in Georgia. The main risk factor for HCV infection in this population of blood donors was previous contact with contaminated blood or blood products. Reliable screening of donors and their blood is critical for controlling the further spread of HCV in Georgia.     

江苏某地区既往有偿献血人群HCV感染状况及相关因素研究

目的 探索江苏某地区既往有偿献血人群HCV感染的流行状况,分析与HCV感染转归及HCV RNA载量相关的因素。方法 对该地区50岁以上人群开展横断面研究,采用问卷方式收集研究对象信息,并对其进行肝脏B超检查及相关指标检查。应用EpiData和Stata软件对数据进行录入及统计学分析。结果 该地区1601名50岁以上人群中HCV感染率为22.55%,516名既往有偿献血人群HCV感染率为61.05%。多元逐步回归显示, ALT及AST与HCV感染转归之间存在相关性,OR值分别为1.38(95%CI:1.18~1.62)及1.30(95%CI:1.10~1.54)。FPG与HCV RNA病毒载量之间存在相关性(OR=1.17,95%CI:1.01~1.35)。结论 该地区HCV感染率较高,临床上ALT、AST以及FPG的检测结果与HCV的感染转归风险及病毒活动能力之间存在关联。     

HLA-DQ基因遗传变异与丙型肝炎病毒感染转归的相关性研究

目的 探讨遗人类白细胞抗原（human leukocyte antigen,HLA）DQ基因多态性与丙型肝炎感染转归的关联。方法 应用TaqMan探针方法检测339例丙型肝炎病毒（hepatitis C virus,HCV）持续感染者,262例HCV自限感染者和942例健康对照者HLA-DQ基因rs2856718和rs7453920位点的基因多态性,比较不同基因型与丙型肝炎病毒感染转归的关系。结果 采用多因素Logistic回归分析,结果显示rs2856718位点杂合基因型AG在感染组中的频率均低于对照组（调整OR=0.73,95%CI:0.56~0.94）;另外,rs7453920 AA基因型可增加个体对HCV的易感性（调整OR=1.75,95%CI:1.01~3.03）。结果显示,与AG单倍型相比,携带AA单倍型的个体可增加丙型肝炎易感性（调整OR=1.67,95%CI:1.11~2.52）。分层分析结果发现,在男性人群中,rs2856718位点的杂合基因型AG在感染组中的频率低于对照组（调整OR=0.68,95%CI:0.51~0.93）;在45~60岁人群中,rs7453920位点突变纯合基因型GG在感染组中的频率高于对照组（调整OR=2.35,95%CI:1.11~4.98）。结论 HLA-DQ基因多态性与丙型肝炎病毒感染转归存在关联。     

Risk factors for hepatitis C virus infection. A case-control study of blood donors in the Trent Region (UK).

The introduction of screening for hepatitis C virus (HCV) by the National Blood Transfusion Service identified donors who had acquired HCV infection. We undertook a case-control study amongst blood donors in the Trent Region to determine risks for HCV infection. A total of 74 blood donors confirmed positive for hepatitis C infection and 150 age, sex and donor venue matched controls were included in the study. Fifty-three percent of hepatitis C infected blood donors reported previous use of injected drugs compared to no controls; relative risk (RR) not estimatable (lower limit 95% CI = 20). Other risk factors were a history of: receipt of a blood transfusion or blood products RR = 3.6 (95% CI 1.5-8.3), having been a ''health care worker'' RR = 2.8 (95% CI 1.1-7.6), tattooing RR = 3.3 (95% CI 1.2-8.7), and an association with having been born abroad RR = 3.2 (95% CI 1.1-9.5). No risk was shown for a history of multiple sexual partners, ear piercing or acupuncture. Injecting drug use explains more than 50% of hepatitis C infections in blood donors, a group who are less likely to have injected drugs than the general population.     

An incident case-control study of modes of hepatitis C virus transmission in France

PURPOSE: Risk factors for hepatitis C virus (HCV) infection have rarely been estimated using incident case-control studies in the "general" population. We undertook a case-control study of incident HCV infection to identify persistent modes of transmission in France. METHODS: Two types of case-patients were included: (1) repeat blood donors who seroconverted between 1998 and 2001 (with a last negative third-generation test reported from 1995 or after) and (2) seroconverters referred to hepatology departments in 2000 through 2001. For each case-patient, four age- and sex-matched controls were randomly selected from the population of occurrence. Data on risk factors were recorded for each case-patient's and matched control's referent exposure period (between last negative and first positive tests). RESULTS: Sixty-four case-patients and 227 controls were included. In univariate analysis, endoscopy (matched odds ratios [mORs] = 8.0; 95% confidence intervals [CI] = 2.3-27.2), general anesthesia (mOR = 5.6; 95% CI = 2.2-14.7), tattooing or body piercing (mOR = 8.8; 95% CI = 1.7-44.1), and intravenous (IV) drug use (p < 0.0001; mOR not defined) were associated with HCV seroconversion. In multivariate analysis, risk factors associated with HCV seroconversion were drug use (adjusted OR [aOR] = 109.0; 95% CI = 11.7-1015.8), digestive endoscopy (aOR = 5.7; CI = 1.4-23.8), and invasive radiology procedures (aOR = 11.6; CI = 1.7-78.5). CONCLUSIONS: The results showed the continuing major role of IV drug use and suggested that transmission related to invasive health care remained a potential source of new HCV infection between 1995 and 2001.     

Risk factors associated with hepatitis C virus infection in Taiwanese government employees

This study evaluated the roles of multiple factors in hepatitis C virus (HCV) infection, with emphasis on the modification of various individual characteristics on the risk associated with percutaneous exposure to blood. Serum samples taken from 4869 men in Taiwan within a cohort study were tested for HCV antibody. The overall positive rate of anti-HCV was 1.6%. In a logistic regression, factors positively associated with anti-HCV positivity were previous blood transfusion (odds ratio [OR] = 7.28: 95% confidence interval [CI] = 4.26-12.45), a history of surgery (OR = 2.06: 95% CI = 1 23-3.46), and lower educational levels (OR = 1.94; 95% CI = 1.14-3.32). The anti-HCV positive rate was significantly lower in hepatitis B surface antigen (HBsAg) carriers than in non-carriers (OR = 0.60; 95% CI = 0.37-0.95). Ageing, lower educational levels, O blood group, and Taiwanese ethnicity enhanced the likelihood of HCV infection through blood transfusion/surgery, whereasHBsAg status, cigarette smoking, and habitual alcohol drinking reduced it.     

Use of exogenous hormones by women and lung cancer: evidence from the Royal College of General Practitioners' Oral Contraception Study

OBJECTIVE: The objective of this study was to assess the risk of lung cancer among women who have used oral contraception or hormone replacement therapy (HRT), especially those exposed to both classes of exogenous hormones. DESIGN: This study is a nested case-control one using prospectively collected data from the Royal College of General Practitioners' Oral Contraception Study (OCS). The 162 case patients were women with a diagnosis of lung cancer recorded on the OCS database by August 2004. Each case patient was matched with 3 control subjects who were free of the disease at the time of the case patient's diagnosis, of similar age and with similar length of follow-up in the OCS. RESULTS: Compared with never use, current use of oral contraception was associated with a statistically nonsignificant reduced risk of lung cancer, with an adjusted odds ratio (OR) of 0.47 and a 95% confidence interval (CI) of 0.08-2.95 (OR=0.86 and 95% CI=0.50-1.48 for former use; OR=0.84 and 95% CI=0.49-1.43 for ever use). Similar comparisons for HRT were current use (OR=1.21, 95% CI=0.23-6.37), former use (OR=0.62, 95% CI=0.23-1.68) and ever use (OR=0.71, 95% CI=0.28-1.78). The OR among women who had used both classes of hormones was 0.53 (95% CI=0.16-1.72), as compared with those who had used neither. CONCLUSIONS: Our results are compatible with findings from other studies that suggest that oral contraceptives may reduce the risk of lung cancer. Evidence for a beneficial effect of HRT is less convincing. Further study is needed to determine how long any benefit lasts and whether it is stronger in women exposed to both classes of exogenous hormones. The small number of events occurring in this very large cohort, however, shows that any public health benefit is likely to be marginal.     

重庆市主城区居民无偿献血KAP状况调查及影响因素研究

目的 了解重庆市主城区居民无偿献血相关知识、态度和行为（KAP）现状,分析其影响因素,为提高居民无偿献血积极性提供针对性建议。方法 根据知信行理论自行设计调查问卷,采用方便抽样方法对重庆市主城9区居民进行抽样调查。结果 年龄、学历、职业、献血史是居民无偿献血知识认知情况的影响因素,≤19岁（OR = 3.804,95% CI:1.739～8.325）、20～29岁（OR = 2.725,95% CI:1.532～4.846）、本科/大专（OR = 2.356,95% CI:1.469～3.779）、硕士及以上学历（OR = 3.597,95% CI:1.771～7.305）、有献血史（OR = 4.272,95% CI:2.898～6.298）居民对无偿献血知识认知程度更高,个体工商户（OR = 0.500,95% CI:0.305～0.820）、农民/农民工（OR = 0.300,95% CI:0.143～0.628）、离/退休（OR = 0.286,95% CI:0.087～0.934）居民认知程度较低;学历、献血史是居民无偿献血态度的影响因素,居民献血意愿随学历呈现逐渐增高的趋势,有献血史居民（OR = 1.443,95% CI:1.028～2.025）献血意愿更强;职业是居民无偿献血行为的影响因素,农民/农民工（OR = 0.352,95% CI:0.147～0.847）献血率较低。结论 重庆市居民无偿献血知识认知较高,献血意愿较强,但献血行为有待改善。     

A population-based case-control study of risk factors for neural tube defects in four high-prevalence areas of Shanxi province, China

Shanxi province in Northern China has one of the highest reported prevalence rates of neural tube defects (NTD) in the world. To explore the risk factors for NTDs in Shanxi province, we carried out a population-based case-control study in four selected counties with prevalence rates >10 per 1000 births during 2003. Using a multi-logistic regression model analysis (alpha = 0.10), 158 NTD cases were compared with 226 control mothers. Maternal factors significantly associated with increased risk for an NTD were a primary school education or lower (adjusted odds ratio [OR] 2.32, 95% confidence interval [CI] 1.09, 4.97); a history of a previous birth defect-affected pregnancy (adjusted OR 5.27, 95% CI 0.98, 28.37); history of a fever or 'cold' (adjusted OR 3.36, 95% CI 1.68, 6.72); use of analgesic and antipyretic drugs (adjusted OR 4.89, 95% CI 0.92, 25.97); daily passive exposure to cigarette smoke (adjusted OR 1.60, 95% CI 0.94, 2.73); poor ventilation during heating (adjusted OR 3.91, 95% CI 0.75, 20.81); and consumption of >or= six meals per week containing pickled vegetables (adjusted OR 3.86, 95% CI 1.11, 13.47) during pregnancy. Factors which appeared to be protective were meat consumption one to three times per week (adjusted OR 0.62, 95% CI 0.37, 1.06), or >or= four times per week (adjusted OR 0.28, 95% CI 0.11, 0.77); and legume consumption >or= six times per week (adjusted OR 0.39, 95% CI 0.17, 0.89). Differences in risk were found between the two most common phenotypes, anencephaly and spina bifida. Most of the environmental factors had stronger positive and negative associations with risk for anencephaly rather than spina bifida, whereas history of a previous birth defect-associated pregnancy, as well as legume consumption, were more strongly associated with the risk for spina bifida than for anencephaly. The findings suggest that aetiological heterogeneity may exist between anencephaly and spina bifida.