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Crane PK, Gibbons LE, Jolley L, van Belle G. Differential item functioning analysis with ordinal logistic regression techniques. DIFdetect and difwithpar. Med Care 2007; 44:S115-23. [PMID: 17060818 DOI: 10.1097/01.mlr.0000245183.28384.ed] [Citation(s) in RCA: 213] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
INTRODUCTION We present an ordinal logistic regression model for identification of items with differential item functioning (DIF) and apply this model to a Mini-Mental State Examination (MMSE) dataset. We employ item response theory ability estimation in our models. Three nested ordinal logistic regression models are applied to each item. Model testing begins with examination of the statistical significance of the interaction term between ability and the group indicator, consistent with nonuniform DIF. Then we turn our attention to the coefficient of the ability term in models with and without the group term. If including the group term has a marked effect on that coefficient, we declare that it has uniform DIF. We examined DIF related to language of test administration in addition to self-reported race, Hispanic ethnicity, age, years of education, and sex. METHODS We used PARSCALE for IRT analyses and STATA for ordinal logistic regression approaches. We used an iterative technique for adjusting IRT ability estimates on the basis of DIF findings. RESULTS Five items were found to have DIF related to language. These same items also had DIF related to other covariates. DISCUSSION The ordinal logistic regression approach to DIF detection, when combined with IRT ability estimates, provides a reasonable alternative for DIF detection. There appear to be several items with significant DIF related to language of test administration in the MMSE. More attention needs to be paid to the specific criteria used to determine whether an item has DIF, not just the technique used to identify DIF.
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Chattopadhyay S, Feldgarden M, Weissman SJ, Dykhuizen DE, van Belle G, Sokurenko EV. Haplotype diversity in "source-sink" dynamics of Escherichia coli urovirulence. J Mol Evol 2006; 64:204-14. [PMID: 17177088 DOI: 10.1007/s00239-006-0063-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2006] [Accepted: 10/03/2006] [Indexed: 10/23/2022]
Abstract
FimH, the mannose-specific, type 1 fimbrial adhesin of Escherichia coli, acquires amino acid replacements adaptive in extraintestinal niches (the genitourinary tract) but detrimental in the main habitat (the large intestine). This microevolutionary dynamics is reminiscent of an ecological "source-sink" model of continuous species spread from a stable primary habitat (source) into transient secondary niches (sink), with eventual extinction of the sink-evolved populations. Here, we have adapted two ecological analytical tools-diversity indexes DS and alpha--to compare size and frequency distributions of fimH haplotypes between evolutionarily conserved FimH variants ("source" haplotypes) and FimH variants with adaptive mutations (putative "sink" haplotypes). Both indexes show two- to threefold increased diversity of the sink fimH haplotypes relative to the source haplotypes, a pattern that ran opposite to those seen with nonstructural fimbrial genes (fimC and fimI) and housekeeping loci (adk and fumC) but similar to that seen with another fimbrial adhesin of E. coli, papG-II, also implicated in extraintestinal infections. The increased diversity of the sink pool of adhesin genes is due to the increased richness of the haplotypes (the number of unique haplotypes), rather than their evenness (the extent of similarity in relative abundances). Taken together, this pattern supports a continuous emergence and extinction of the gene alleles adaptive to virulence sink habitats of E. coli, rather than a one-time change in the habitat conditions. Thus, ecological methods of species diversity analysis can be successfully adapted to characterize the emergence of microbial virulence in bacterial pathogens subject to source-sink dynamics.
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Xiong C, van Belle G, Miller JP, Morris JC. Measuring and estimating diagnostic accuracy when there are three ordinal diagnostic groups. Stat Med 2006; 25:1251-73. [PMID: 16345029 DOI: 10.1002/sim.2433] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
This article studies the problem of measuring and estimating the diagnostic accuracy when there are three ordinal diagnostic groups. We use a receiver operating characteristic (ROC) surface to describe the probabilities of correct classifications into three diagnostic groups based on various sets of diagnostic thresholds of a test and propose to use the entire and the partial volume under the surface to measure the diagnostic accuracy. Mathematical properties and probabilistic interpretations of the proposed measure of diagnostic accuracy are discussed. Under the assumption of normal distributions of the diagnostic test from three diagnostic groups, we present the maximum likelihood estimate to the volume under the ROC surface and give the asymptotic variance to the estimate. We further propose several asymptotic confidence interval estimates to the volume under the ROC surface. The performance of these confidence interval estimates is evaluated in terms of attaining the nominal coverage probability based on a simulation study. In addition, we develop a method of sample size determination to achieve an adequate accuracy of the confidence interval estimate. Finally, we demonstrate the proposed methodology by applying it to the clinical diagnosis of early stage Alzheimer's disease based on the neuropsychological database of the Washington University Alzheimer's Disease Research Center.
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Crane PK, Gibbons LE, Jolley L, van Belle G, Selleri R, Dalmonte E, De Ronchi D. Differential item functioning related to education and age in the Italian version of the Mini-mental State Examination. Int Psychogeriatr 2006; 18:505-15. [PMID: 16478571 DOI: 10.1017/s1041610205002978] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2005] [Accepted: 10/06/2005] [Indexed: 11/07/2022]
Abstract
BACKGROUND Differential item functioning (DIF) exists when test item responses by members of different demographic groups are statistically different when controlling for ability. DIF may indicate item bias. Our objective was to determine whether items from the Italian Mini-mental State Examination (MMSE) had DIF related to educational attainment, age, gender and occupation. We were also interested in exploring the significance of DIF in screening tests. METHODS In a two-stage study from Granarolo, Italy, residents over age 61 (n = 495) were evaluated with the Italian MMSE. Those with MMSE scores of 28 or lower were further evaluated for dementia. MMSE results were coded in 10 item bundles. We used ordinal logistic regression to determine whether item bundles had DIF. RESULTS Six of the 10 MMSE item bundles had DIF in educational attainment subgroups. Four of these six bundles also had DIF related to age. Items that required literacy were much harder for those with lower educational attainment. CONCLUSIONS DIF related to education appeared at as few as 3 years of formal schooling. These findings suggest cautious interpretation of data from studies using the Italian MMSE in populations with heterogeneous educational backgrounds. DIF is especially troublesome for two-stage studies that use screening tests.
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Simon GE, Von Korff M, Saunders K, Miglioretti DL, Crane PK, van Belle G, Kessler RC. Association between obesity and psychiatric disorders in the US adult population. ACTA ACUST UNITED AC 2006; 63:824-30. [PMID: 16818872 PMCID: PMC1913935 DOI: 10.1001/archpsyc.63.7.824] [Citation(s) in RCA: 850] [Impact Index Per Article: 47.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
BACKGROUND Epidemiologic data suggest an association between obesity and depression, but findings vary across studies and suggest a stronger relationship in women than men. OBJECTIVE To evaluate the relationship between obesity and a range of mood, anxiety, and substance use disorders in the US general population. DESIGN Cross-sectional epidemiologic survey. SETTING Nationally representative sample of US adults. PARTICIPANTS A total of 9125 respondents who provided complete data on psychiatric disorder, height, and weight. Response rate was 70.9%. MAIN OUTCOME MEASURES Participants completed an in-person interview, including assessment of a range of mental disorders (assessed using the World Health Organization Composite International Diagnostic Interview) and height and weight (by self-report). RESULTS Obesity (defined as body mass index [calculated as weight in kilograms divided by the square of height in meters] of > or =30) was associated with significant increases in lifetime diagnosis of major depression (odds ratio [OR], 1.21; 95% confidence interval [CI], 1.09-1.35), bipolar disorder (OR, 1.47; 95% CI, 1.12-1.93), and panic disorder or agoraphobia (OR, 1.27; 95% CI, 1.01-1.60). Obesity was associated with significantly lower lifetime risk of substance use disorder (OR, 0.78; 95% CI, 0.65-0.93). Subgroup analyses found no difference in these associations between men and women, but the association between obesity and mood disorder was strongest in non-Hispanic whites (OR, 1.38; 95% CI, 1.20-1.59) and college graduates (OR, 1.44; 95% CI, 1.14-1.81). CONCLUSIONS Obesity is associated with an approximately 25% increase in odds of mood and anxiety disorders and an approximately 25% decrease in odds of substance use disorders. Variation across demographic groups suggests that social or cultural factors may moderate or mediate the association between obesity and mood disorder.
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Wang L, Larson EB, Bowen JD, van Belle G. Performance-based physical function and future dementia in older people. ARCHIVES OF INTERNAL MEDICINE 2006; 166:1115-20. [PMID: 16717174 DOI: 10.1001/archinte.166.10.1115] [Citation(s) in RCA: 207] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
BACKGROUND The association of physical function with progression to dementia has not been well investigated. We aimed to determine whether physical function is associated with incident dementia and Alzheimer disease (AD). METHODS We performed a prospective cohort study of 2288 persons 65 years and older without dementia. Patients were enrolled from 1994 to 1996 and followed up through October 2003. Main outcome measures included incident dementia and AD. RESULTS During follow-up 319 participants developed dementia (221 had AD). The age-specific incidence rate of dementia was 53.1 per 1000 person-years for participants who scored lower on a performance-based physical function test at baseline (< or = 10 points) compared with 17.4 per 1000 person-years for those who scored higher (> 10 points). A 1-point lower performance-based physical function score was associated with an increased risk of dementia (hazard ratio, 1.08; 95% confidence interval, 1.03-1.13; P < .001), an increased risk of AD (hazard ratio, 1.06; 95% confidence interval, 1.01-1.12; P = .01), and an increased rate of decline in the Cognitive Ability Screening Instrument scores (0.11 point per year; 95% confidence interval, 0.08-0.14; P < .001) after adjusting for age, sex, years of education, baseline cognitive function, APOE epsilon4 allele, family history of AD, depression, coronary heart disease, and cerebrovascular disease. CONCLUSIONS Lower levels of physical performance were associated with an increased risk of dementia and AD. The study suggests that poor physical function may precede the onset of dementia and AD and higher levels of physical function may be associated with a delayed onset.
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Higdon R, Kolker N, Picone A, van Belle G, Kolker E. LIP index for peptide classification using MS/MS and SEQUEST search via logistic regression. OMICS-A JOURNAL OF INTEGRATIVE BIOLOGY 2005; 8:357-69. [PMID: 15703482 DOI: 10.1089/omi.2004.8.357] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
This study addresses the issue of peptide identification resulting from tandem mass spectrometry proteomics analysis followed by database search. This work shows that the Logistic Identification of Peptides (LIP) Index achieves high sensitivity and specificity for peptide classification relative to a manually verified "gold" standard and also accurately estimates the probability of a correct peptide match. The LIP Index is a weighted average of SEQUEST output variables based on logistic regression models and is a transparent, easy to use, inclusive, extendable, and statistically sound approach to classify correct peptide identifications. Modifications, such as normalizing cross-correlations (Xcorr) for peptide length, adjusting for charge state, and the number of tryptic termini, significantly improve the fit the logistic regression models, as well as increase sensitivity and specificity. The LIP Index also incorporates earlier developed statistical models on spectral quality assessment and peptide identification, which further improves sensitivity and specificity.
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Clark CM, DeCarli C, Mungas D, Chui HI, Higdon R, Nuñez J, Fernandez H, Negrón M, Manly J, Ferris S, Perez A, Torres M, Ewbank D, Glosser G, van Belle G. Earlier Onset of Alzheimer Disease Symptoms in Latino Individuals Compared With Anglo Individuals. ACTA ACUST UNITED AC 2005; 62:774-8. [PMID: 15883265 DOI: 10.1001/archneur.62.5.774] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
BACKGROUND Latino individuals are the largest minority group and the fastest growing population group in the United States, yet there are few studies comparing the clinical features of Alzheimer disease (AD) in this population with those found in Anglo (white non-Latino) patients. OBJECTIVE To compare the age at AD symptom onset in Latino and Anglo individuals. DESIGN Cross-sectional assessment using standardized methods to collect and compare age at AD symptom onset, demographic variables, and medical variables. SETTING Five National Institute on Aging-sponsored Alzheimer's Disease Centers with experience evaluating Spanish-speaking individuals. PATIENTS We evaluated 119 Latino and 55 Anglo patients who had a diagnosis of AD. MAIN OUTCOME MEASURE Age at symptom onset. RESULTS After adjusting for center, sex, and years of education, Latino patients had a mean age at symptom onset 6.8 years earlier (95% confidence interval, 3.5-10.3 years earlier) than Anglo patients. CONCLUSIONS An earlier age at symptom onset suggests that US mainland Latino individuals may experience an increased burden of AD compared with Anglo individuals. The basis for the younger age at symptom onset remains obscure.
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Phillips LE, Longstreth WT, Koepsell T, Custer BS, Kukull WA, van Belle G. Active and Passive Cigarette Smoking and Risk of Intracranial Meningioma. Neuroepidemiology 2005; 24:117-22. [PMID: 15637448 DOI: 10.1159/000082998] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Motivated by prior studies, we examined associations between cigarette smoking and risk of intracranial meningioma in a population-based case-control study, including 200 cases and 2 controls matched to each case on age and sex. Subjects were asked to recall their history of active and passive cigarette smoking occurring 10 or more years before the date of meningioma surgery. Ever active smoking was associated with an increased risk of meningioma in men (OR = 2.1; 95% CI 1.1-4.2) but not in women (OR = 0.7; 95% CI 0.5-1.1). The statistical interaction by gender was significant (p = 0.01). In men, risk increased with increasing number of cigarettes smoked daily (p for trend = 0.04). In women, the trend was opposite (p for trend = 0.08). Among never active smokers, passive smoking from a spouse was associated with increased risk in both sexes (OR 2.0; 95% CI 1.1-3.5), and risk increased with increasing duration of exposure (p for trend = 0.02). Uncertain is whether these findings reflect a true biological phenomenon or result from chance or uncontrolled confounding.
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Shadlen MF, Larson EB, Wang L, Phelan EA, McCormick WC, Jolley L, Teri L, van Belle G. Education modifies the effect of apolipoprotein epsilon 4 on cognitive decline. Neurobiol Aging 2005; 26:17-24. [PMID: 15585342 DOI: 10.1016/j.neurobiolaging.2004.03.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2003] [Revised: 02/26/2004] [Accepted: 03/01/2004] [Indexed: 11/26/2022]
Abstract
OBJECTIVES To assess the influence of education on the association between apolipoprotein E and cognitive change. DESIGN Prospective cohort. PARTICIPANTS HMO-based sample of 2168 non-demented community-dwelling elderly followed over 6 years. MEASUREMENTS Generalized estimating equations were used with the difference between baseline and follow-up cognitive abilities screening instrument (CASI) as the outcome variable. RESULTS At follow-up, 6% of the sample had a decline of 1.5 S.D. or greater on the CASI. Compared to individuals without an APOE4 allele, individuals with a single APOE4 allele did not have greater CASI decline. By contrast, individuals with two APOE4 alleles experienced greater decline in cognitive performance and the magnitude of that decline decreased as years of educational attainment increased. These relationships held after adjusting for age, gender, ethnicity, depression, diabetes, and history of vascular disease. CONCLUSION Lower education was associated with steep 4-year cognitive decline for APOE4 homozygotes but not for APOE4 heterozygotes. Potentially modifiable host factors such as education could influence the association of high-risk genotypes and cognitive decline.
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Wang L, van Belle G, Crane PK, Kukull WA, Bowen JD, McCormick WC, Larson EB. Subjective Memory Deterioration and Future Dementia in People Aged 65 and Older. J Am Geriatr Soc 2004; 52:2045-51. [PMID: 15571540 DOI: 10.1111/j.1532-5415.2004.52568.x] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVES To study whether subjective memory deterioration is associated with future dementia in older people. DESIGN A population-based prospective cohort study begun in 1994 with biennial follow-up interviews. SETTING Community-based members of Group Health Cooperative, a large health maintenance organization in the Seattle area. PARTICIPANTS A sample of 1,883 subjects, dementia free, aged 65 and older, who scored 91 or higher on the 100-point Cognitive Ability Screening Instrument (CASI) at study entry. MEASUREMENTS Subjective memory was assessed by asking whether memory had changed on 5-point Likert scales (e.g., 1=definitely improved, 3=no change, 5=definitely deteriorated) with regard to five items: remembering names, faces, friends, and appointments and judging the time. The items were summed for a possible total score ranging from 5 to 25. Subjective memory deterioration was defined as present if the total score was 20 or above. Cognitive performance was measured using the CASI. Incident dementia cases were identified using Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria. RESULTS Of 1,883 subjects, 126 developed dementia during 5 years of follow-up. Subjective memory deterioration was associated with cognitive decline and incident dementia. Age modified the association between subjective memory deterioration and future dementia. For persons reporting subjective memory deterioration at the ages of 70, 75, and 80, the hazard ratios of developing dementia were 6.0 (95% confidence interval (CI)=2.1-18), 3.2 (95% CI=1.6-6.2) and 1.6 (95% CI=0.86-3.1), respectively. CONCLUSION Subjective memory deterioration was found to precede the development of dementia in older people with normal cognitive screening results. These findings suggest that a high level of subjective memory deterioration in persons with normal objective cognitive function may identify a subset of individuals at greater risk for developing dementia.
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Beekly DL, Ramos EM, van Belle G, Deitrich W, Clark AD, Jacka ME, Kukull WA. The National Alzheimer's Coordinating Center (NACC) Database: an Alzheimer disease database. Alzheimer Dis Assoc Disord 2004; 18:270-7. [PMID: 15592144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/01/2023]
Abstract
The National Alzheimer's Coordinating Center (NACC) is responsible for developing and maintaining a database of patient information collected from the 29 Alzheimer disease centers (ADCs) funded by the National Institute on Aging. Each of the centers collects center-determined data elements on patients enrolled into its center and transmits a minimum dataset to NACC. Data are managed differently at each center depending on that center's research needs. The centers' data systems vary from a single personal computer running spreadsheet software to a network of servers running an advanced data management system such as Oracle. The challenge for NACC is to expand and adjust previously collected data elements into an integrated database that could be used for administrative as well as research purposes. In addition, NACC sought to allow the centers to have the flexibility they needed for data submission. To accomplish this task, NACC designed a database that contained separate specific datasets each with individual data elements. NACC also designed a data management system to easily collect and manage these data. The NACC web site (www.alz.washington.edu) was created to allow access to the data.
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Koepsell TD, Kukull WA, Beekly D, van Belle G, Higdon R, Fitzpatrick A, Kurland B. P3-110 Public-use data from NACC. Neurobiol Aging 2004. [DOI: 10.1016/s0197-4580(04)81262-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Crane P, van Belle G, Higdon R, Kurland B, Larson E. P2-244 The implications of differential item functioning on epidemiological studies of Alzheimer disease: the case of the act study. Neurobiol Aging 2004. [DOI: 10.1016/s0197-4580(04)80990-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Crane PK, van Belle G, Larson EB. Test bias in a cognitive test: differential item functioning in the CASI. Stat Med 2004; 23:241-56. [PMID: 14716726 DOI: 10.1002/sim.1713] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Assessment of test bias is important to establish the construct validity of tests. Assessment of differential item functioning (DIF) is an important first step in this process. DIF is present when examinees from different groups have differing probabilities of success on an item, after controlling for overall ability level. Here, we present analysis of DIF in the Cognitive Assessment Screening Instrument (CASI) using data from a large cohort study of elderly adults. We developed an ordinal logistic regression modelling technique to assess test items for DIF. Estimates of cognitive ability were obtained in two ways based on responses to CASI items: using traditional CASI scoring according to the original test instructions as well as using item response theory (IRT) scoring. Several demographic characteristics were examined for potential DIF, including ethnicity and gender (entered into the model as dichotomous variables), and years of education and age (entered as continuous variables). We found that a disappointingly large number of items had DIF with respect to at least one of these demographic variables. More items were found to have DIF with traditional CASI scoring than with IRT scoring. This study demonstrates a powerful technique for the evaluation of DIF in psychometric tests. The finding that so many CASI items had DIF suggests that previous findings of differences between groups in cognitive functioning as measured by the CASI may be due to biased test items rather than true differences between groups. The finding that IRT scoring diminished the impact of DIF is discussed. Some preliminary suggestions for how to deal with items found to have DIF in cognitive tests are made. The advantages of the DIF detection techniques we developed are discussed in relation to other techniques for the evaluation of DIF.
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Longstreth WT, Phillips LE, Drangsholt M, Koepsell TD, Custer BS, Gehrels JA, van Belle G. Dental X-rays and the risk of intracranial meningioma: a population-based case-control study. Cancer 2004; 100:1026-34. [PMID: 14983499 DOI: 10.1002/cncr.20036] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
BACKGROUND Ionizing radiation is a likely cause of intracranial meningioma. The authors determined whether the risk of intracranial meningioma was associated with past dental X-rays-specifically, posterior bitewings, full-mouth series, and lateral cephalometric and panoramic radiographs. METHODS The authors conducted a population-based case-control study of residents of King, Pierce, and Snohomish counties in western Washington State. Case patients (n = 200) had an incident intracranial meningioma that was confirmed histologically during life between January 1995 and June 1998. The authors used random-digit dialing and Medicare eligibility lists to identify two control subjects to be matched to each case patient based on age and gender. Exposures were determined during an in-person interview. The authors compared self-report and dental records in a subset of study participants. RESULTS Of the 4 dental X-ray procedures evaluated, only the full-mouth series (specifically, > or = 6 over a lifetime) was associated with a significantly increased risk of meningioma (odds ratio, 2.06; 95% confidence limits, 1.03-4.17). However, evidence for a dose-response relation was lacking (P for trend = 0.33). The risk was elevated with the aggregate number of full-mouth series in 10-year periods from approximately 15-40 years before diagnosis, with significant elevations in the 10-year periods beginning 22-30 years before diagnosis. The risks in these analyses were even greater when only women were considered. CONCLUSIONS Dental X-rays involving full-mouth series performed 15-40 years ago, when radiation exposure from full-mouth series was much greater than it is now, were associated with an increased risk of meningioma. The authors did not observe an increased risk with bitewings, lateral cephalometric, and panoramic radiographs.
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Olsen GW, Church TR, Larson EB, van Belle G, Lundberg JK, Hansen KJ, Burris JM, Mandel JH, Zobel LR. Serum concentrations of perfluorooctanesulfonate and other fluorochemicals in an elderly population from Seattle, Washington. CHEMOSPHERE 2004; 54:1599-1611. [PMID: 14675839 DOI: 10.1016/j.chemosphere.2003.09.025] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Perfluorooctanesulfonyl fluoride (POSF, C8F17SO2F) related-materials have been used as surfactants, paper and packaging treatments, and surface (e.g., carpet, textile, upholstery) protectants. A metabolite, perfluorooctanesulfonate (PFOS, C8F17SO3-), has been identified in the serum and liver of non-occupationally exposed humans and wildlife. Because of its persistence, an important question was whether elderly humans might have higher PFOS concentrations. From a prospective study designed to examine cognitive function in the Seattle (WA) metropolitan area, blood samples were collected from 238 dementia-free subjects (ages 65-96). High-pressure liquid chromatography-electrospray tandem mass spectrometry determined seven fluorochemicals: PFOS; N-ethyl perfluorooctanesulfonamidoacetate; N-methyl perfluorooctanesulfonamidoacetate; perfluorooctanesulfonamidoacetate; perfluorooctanesulfonamide; perfluorooctanoate; and perfluorohexanesulfonate. Serum PFOS concentrations ranged from less than the lower limit of quantitation (3.4 ppb) to 175.0 ppb (geometric mean 31.0 ppb; 95% CI 28.8-33.4). An estimate of the 95% tolerance limit was 84.1 ppb (upper 95% confidence limit 104.0 ppb). Serum PFOS concentrations were slightly lower among the most elderly. There were no significant differences by sex or years residence in Seattle. The distributions of the other fluorochemicals were approximately an order of magnitude lower. Similar to other reported findings of younger adults, the geometric mean serum PFOS concentration in non-occupational adult populations likely approximates 30-40 ppb with 95% of the population's serum PFOS concentrations below 100 ppb.
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Kukull WA, Higdon R, Bowen JD, McCormick WC, Teri L, Schellenberg GD, van Belle G, Jolley L, Larson EB. Dementia and Alzheimer disease incidence: a prospective cohort study. ARCHIVES OF NEUROLOGY 2002; 59:1737-46. [PMID: 12433261 DOI: 10.1001/archneur.59.11.1737] [Citation(s) in RCA: 545] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
CONTEXT Age-specific incidence rates for dementia and Alzheimer disease (AD) are important for research and clinical practice. Incidence estimates for the United States are few and vary with the population sampled and study design; we present data that will contribute to a consensus of these rates. OBJECTIVES To provide age-specific incidence estimates for dementia and AD and to estimate the association of sex, educational level, and apolipoprotein E genotype with onset. DESIGN Prospective cohort study; begun in 1994 with follow-up interviews every 2 years. SETTING Members of community-based, large health maintenance organization with demographics consistent with the surrounding base population; diagnostic evaluation by university-based study clinicians. SUBJECTS Random sample of subjects aged 65 years or older from the base population; dementia free, nonnursing home residents. Of 5422 who were eligible, 2581 were enrolled, and 2356 had at least 1 follow-up evaluation (10 591 person-years of observation). MAIN OUTCOME MEASURE Dementia and Alzheimer disease diagnoses were based on standard criteria. Age-specific incidence rates were calculated using a person-years approach with Poisson distribution confidence intervals. Cox proportional hazards model analysis was used to examine other factors. RESULTS Two hundred fifteen cases of dementia and 151 cases of AD were diagnosed. Incidence rates for dementia and AD increase across the 5-year age groups; AD rates rise from 2.8 per 1000 person-years (age group, 65-69 years) to 56.1 per 1000 person-years in the older than 90-year age group. The rates nearly triple from the 75-to-79-year and 80-to-84-year age groups, but the relative increase is much less thereafter. Sex was not associated with AD onset. Educational level (>15 years vs <12 years) was associated with a decreased risk of AD; however, the association was also dependent on the baseline cognitive screening test score. CONCLUSIONS Our dementia and AD incidence rates are consistent with recent US and European cohort studies, providing clinicians and researchers new information concerning the reproducibility of incidence estimates across settings. Increased risk was associated with age and the apolipoprotein E genotype; also with a low baseline cognitive screening test score. Educational level was inversely associated with the risk of dementia and positively associated with the baseline cognitive test score; thus, detection of AD by the screening test could also be influenced by educational level.
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Wang L, van Belle G, Kukull WB, Larson EB. Predictors of functional change: a longitudinal study of nondemented people aged 65 and older. J Am Geriatr Soc 2002; 50:1525-34. [PMID: 12383150 DOI: 10.1046/j.1532-5415.2002.50408.x] [Citation(s) in RCA: 227] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVES To identify factors associated with functional change in an older population and investigate interactions among selected potential risk factors. DESIGN A population-based prospective cohort study. SETTING A random sample was selected from the Group Health Cooperative members in the Seattle area from 1994 to 1996 and followed biennially. PARTICIPANTS Two thousand five hundred eighty-one people aged 65 and older, cognitively intact at baseline. MEASUREMENTS Functional status was measured by activities of daily living, instrumental activities of daily living, and performance-based physical function testing. RESULTS The cohort status at the time of these analyses was: deceased, 391; withdrawn, 179; dementia, 152; and on study, 1,873. The mean follow-up time was 3.4 years. Using linear regressions with Generalized Estimating Equation, selected medical conditions (diabetes mellitus, hypertension, coronary heart disease, cerebrovascular disease (CVD), osteoporosis, arthritis, and cancer), low cognitive function, depression, and smoking were associated with worse functional outcomes. Exercise and moderate alcohol use were associated with better functional outcomes. Over the follow-up period, coronary heart disease, CVD, and depression were associated with increased rates of functional decline. Exercise and moderate alcohol consumption were associated with decreased rates of functional decline. Significant interactions were observed between exercise and coronary heart disease, moderate alcohol use and CVD, and cognition and CVD. CONCLUSIONS Our study has identified not only risk factors associated with functional decline but also the interactions among these factors. These observations, along with other published research, add to the growing understanding of the underlying process of functional change and could provide a basis to design effective strategies to delay functional decline.
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Gibbons LE, van Belle G, Yang M, Gill C, Brayne C, Huppert FA, Paykel E, Larson E. Cross-cultural comparison of the Mini-Mental State examination in United Kingdom and United States participants with Alzheimer's disease. Int J Geriatr Psychiatry 2002; 17:723-8. [PMID: 12211121 DOI: 10.1002/gps.683] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
OBJECTIVES the relative difficulties of items on the Mini-Mental State Examination (MMSE) were compared in English-speaking Alzheimer's disease (AD) patients in the United States (US) and United Kingdom (UK). METHODS participants were aged 75 and over, with a clinical diagnosis of AD according to standardized methods. Initial MMSE scores from an AD patient registry in the US (n = 401), and a field survey in the UK (n = 139) were compared. Item Characteristic Curve analysis (ICC) was used to calculate the relative difficulty of individual MMSE items, adjusted for the remaining MMSE items. Age, gender, education, and severity of disease were evaluated as possible confounders. RESULTS UK participants found it relatively more difficult to name their county than US participants did to name their state. The relative difficulties of registration and recall, repeating a phrase, and following verbal directions also were significantly higher for the UK participants, even after adjustment for other factors. CONCLUSIONS differences between the cohorts could be explained by translation artifacts in the test items or by cultural differences in the manifestation of AD. In this study, most, if not all differences can be explained by the former. ICC analysis can be used to develop tests that are functionally equivalent, a prerequisite for comparing dementia in different populations.
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Guffey SE, Flanagan ME, van Belle G. Air Sampling at the Chest and Ear as Representative of the Breathing Zone. ACTA ACUST UNITED AC 2001. [DOI: 10.1202/0002-8894(2001)062<0416:asatca>2.0.co;2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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D'Agostino RB, Fisher LD, van Belle G. Biostatistics: A Methodology for the Health Sciences. J Am Stat Assoc 1995. [DOI: 10.2307/2291095] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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van Belle G, Martin DC. Sample Size as a Function of Coefficient of Variation and Ratio of Means. AM STAT 1993. [DOI: 10.2307/2684968] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Haggitt RC, van Belle G, Reid BJ. Reply. Hum Pathol 1988. [DOI: 10.1016/s0046-8177(88)80246-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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