ISSN:1044-3983    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:1044-3983    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:1044-3983    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:1044-3983    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Background.It is generally agreed that adjustment for measurement error (when feasible) can substantially increase the validity of epidemiologic analyses. Although a broad variety of methods for measurement error correction has been developed, application in practice is rare. One reason may be that little is known about the robustness of these methods against violations of their restrictive assumptions.Methods.We carried out a simulation study to assess the performance of two error correction methods (a regression calibration method and a semiparametric approach) as compared with standard analyses without measurement error correction in case-control studies with internal validation data. Performance was assessed over a wide range of model parameters including varying degrees of violations of assumptions.Results.In nearly all the settings assessed, the semiparametric estimate performed better than all alternatives under investigation. The regression calibration method is sensitive to violations of the assumptions of nondifferential error and small error variance.Conclusions.The semiparametric method is a very robust method to correct for measurement error in case-control studies, but lack of functional software hinders widespread use. If the assumptions for the regression calibration method are fulfilled, application of this method, originally developed for cohort studies, in case-control studies may be a useful alternative that is easy to implement.

ISSN:1044-3983    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Background.In the United States, more people kill themselves with firearms than with all other methods combined. A central question regarding the relation between firearms and suicide is whether the ready availability of firearms increases the suicide rate, rather than merely increasing the proportion of suicides from guns.Methods.We used publicly available data for the nine regions and 50 states in the United States over a 10-year period (1988–1997) to examine the association between levels of household firearm ownership and rates of suicide, firearm suicide, and non-firearm suicide by age groups and gender.Results.In both regional and state-level analyses, for the U.S. population as a whole, for both males and females, and for virtually every age group, a robust association exists between levels of household firearm ownership and suicide rates.Conclusions.Where firearm ownership levels are higher, a disproportionately large number of people die from suicide.

ISSN:1044-3983    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Background.Some children have been killed by air bags, leading to advice that young children should not sit in front of an active air bag.Methods.We conducted a case-control study to estimate the association of passenger air bag presence with death, according to passenger age and seat belt use. We used data from crashes on U.S. public roads in 1992 through 1998. Cases (N = 20,987) were front seat passengers who died, and controls (N = 69,277) were a sample of survivors.Results.Among restrained passengers, the adjusted relative risk of death for those with a passenger air bag was 0.79 (95% confidence interval [CI] = 0.66–0.94); for children 12 years or younger the adjusted relative risk was 1.05 (0.69–1.59), and for adults 20 years or older it was 0.75 (0.63–0.91). Among unrestrained passengers, the adjusted relative risk was 1.03 (CI = 0.81–1.30); for children 12 years or younger the adjusted relative risk was 1.37 (0.90–2.10), and for adults 20 years or older it was 0.97 (0.75–1.24).Conclusions.Passenger air bags may be a hazard to unrestrained children and of little benefit to unrestrained adults. Our results support the advice that children younger than 13 years should not sit in front of an active air bag.

ISSN:1044-3983    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Background.Group BStreptococcuscauses morbidity and mortality among newborns, pregnant women, and nonpregnant adults. Among adults, sexual and fecal-oral routes of transmission are hypothesized; this study addresses whether sexual transmission occurs.Methods.Our outcome of interest was group BStreptococcus. From our investigation of the heterosexual transmission of urinary tract infections among college students at the University of Michigan, conducted in 1996–1999, we identified 120 couples in which one or both partners carried group BStreptococcus. Each partner completed a questionnaire regarding potential risk factors for colonization.Results.Co-colonization with the identical group BStreptococcusstrain (as determined by pulsed-field gel electrophoresis) occurred in 86% of the 57 co-colonized couples. When the male sex partner carried group BStreptococcus, 64% of female partners also were colonized; conversely, 49% of male partners of colonized females were colonized with identical strains. Among behaviors predicting co-colonization within the partnership, male-to-female oral sex was a risk factor among both women (odds ratio [OR] = 2.9; 95% confidence interval [CI] = 1.2–6.9) and men (OR = 2.5; CI = 1.1–5.6). First sex at age 20 years or older was associated with an increased risk among women (OR = 2.1; CI = 0.7–6.4) and among men (OR = 3.0; CI = 1.0–9.3), and four or more lifetime sex partners was associated with a decreased risk of co-colonization among women (OR = 0.6; CI = 0.2–1.5) and among men (OR = 0.4; CI = 0.2–1.0).Conclusions.Among heterosexual college couples, sexual activity, particularly male-to-female oral sex, increases the risk of co-colonization with an identical group BStreptococcusstrain. Future studies should evaluate the role of the pharynx and examine the effects of both bacterial characteristics and host response on transmission.

ISSN:1044-3983    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Background.To evaluate associations between exposure to disinfection byproducts in drinking water and adverse birth outcomes, personal exposure to disinfection byproducts must take into consideration multiple routes of exposure.Methods.We assessed the reproducibility and validity of a questionnaire measuring water consumption, showering and bathing habits, use of chlorine-based products, and swimming pool attendance in 237 pregnant Italian women enrolled between June and December 1999. The questionnaire was completed during the last trimester of pregnancy (preQ) and again a few days after delivery (postQ). Data from postQ were compared with a 7-day diary completed during the last trimester.Results.According to postQ, total water intake was 2.6 liters per day, whereas tap water intake was 0.6 liters per day. Intraclass correlation coefficients of postQ compared with preQ were 0.85 for tap water daily intake and 0.77 for duration of showering and bathing. Pearson's correlation coefficients were 0.84 for tap water daily intake, 0.81 for frequency of showering, and 0.94 for bathing. The kappa statistics were 0.76 (95% confidence limits = 0.68, 0.85) for use of domestic chlorine-based products and 0.82 (0.70, 0.94) for indoor swimming. Pearson's coefficients for postQ compared with the diary were 0.78 for tap water daily intake, 0.62 for frequency of showering, and 0.64 for bathing. Compared with the diary, the sensitivity and specificity of postQ in assessing indoor swimming were 75% and 90%, respectively.Conclusions.The questionnaire appears to be a valid and reliable method for assessing exposure to disinfection byproducts in the last trimester of pregnancy.

ISSN:1044-3983    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

The future of genetic studies of complex human diseases will rely more and more on the epidemiologic association paradigm, in particular the use of the transmission/disequilibrium test to detect linkage disequilibrium in a case-parents study. With the rapid progress in genomic studies, many single nucleotide polymorphisms will be identified and genotyped within a very short physical distance. Analyzing multiple single nucleotide polymorphisms within a candidate gene/region with Bonferroni correction for multiple transmission/disequilibrium tests will lead to a conservative test, and hence a power loss. I propose a new method, the “Adaptive PRIncipal COmponent Test” (APRICOT). The method has the following properties: (1) it does not need haplotype information; (2) it is nonparametric—it does not make specific assumptions about the population history or population structure; and (3) the calculation of the test statistic and the determination of its significance level are simple and straightforward. Monte-Carlo simulation reveals that adaptive principal component test maintains the nominal significance level under the null hypothesis of no linkage disequilibrium, even under complex situations of multiple ancestral haplotypes and structured populations. It provides a substantial power advantage over the conventional Bonferroni approach. The adaptive principal component test is a promising method for candidate gene testing using single nucleotide polymorphisms.

ISSN:1044-3983    

出版商:OVID    

年代:2002

数据来源: OVID