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PubMed2006

An isotopic method for quantifying sweeteners derived from corn and sugar cane.

BACKGROUND: Consumption of high-fructose corn syrup, as well as cane sugar, has been implicated in the rise of the obesity and diabetes epidemics. To date, however, no reliable biomarker for the consumption of these sweeteners is available. OBJECTIVE: The objective of the study was to determine the natural abundance stable-carbon-isotope signature of commonly consumed foods of plant origin. DESIGN: Samples from approximately 100 plant-derived food products purchased from local grocery stores were analyzed for 13C content by using stable-isotope mass spectroscopy. RESULTS: Measurement of natural abundance ratios of 13C to 12C in approximately 100 off-the-shelf foods found a distinct range of values for corn- and sugar cane-derived foods, particularly those rich in high-fructose corn syrup. CONCLUSION: A new technique, in which consumption of these foods may be estimated in humans by measuring the natural abundance stable-carbon-isotope profile of corn- and sugar cane-sweetened or sugar-containing foods as tracked in tissue or blood, could potentially provide an objective assessment of dietary intake and offer new opportunities for the study of diet-disease relations.

Algorithms↗
PubMed2000

Survival, functional limitations, and self-rated health in the NHANES I Epidemiologic Follow-up Study, 1992. First National Health and Nutrition Examination Survey.

This study examined relative hazards for mortality and functional limitations according to poor self-ratings of health using prospective data from the NHANES I Epidemiologic Follow-up Study, a representative sample of US adults aged 25-74 years that has been followed since the First National Health and Nutrition Examination Survey (NHANES I) was conducted in 1971-1975. Follow-up data were taken from death records and from the 1982 and 1992 reinterviews. Respondents (n = 6,913) provided extensive baseline data through physician examinations, laboratory testing, and self-reports of conditions, symptoms, and risk behaviors. Functional limitations were assessed among survivors in 1982 and 1992. Cox regression models accounting for sample design indicated that baseline self-rated health was associated with a significantly reduced hazard of mortality for males but not for females through 1992; adjusted hazards ratios for excellent health as compared with poor health were 0.52 for males (95% confidence interval: 0.36, 0.73) and 0.80 for females (95% confidence interval: 0.51, 1.23). Self-rated health also predicted 1982 and 1992 functional limitation for both men and women and 1992 function net of 1982 function for men only. Self-rated health contributes unique information to epidemiologic studies that is not captured by standard clinical assessments or self-reported histories, but evidence suggests that the effect may be stronger for men than for women.

Activities of Daily Living↗
PubMed2003

Influences of asthma and household environment on lung function in children and adolescents: the third national health and nutrition examination survey.

The authors examined influences of asthma and household environment (passive smoking, use of a gas stove, and having a dog or cat) on five measures of spirometric lung function among 8- to 16-year-old subjects, as measured cross-sectionally in the Third National Health and Nutrition Examination Survey (NHANES III) (1988-1994). In regression models, independent variables included asthma status, household environmental factors, age, and anthropometric measurements. Regression analyses were weighted by the NHANES III examination sample weighting factor, and results were adjusted for clustering in the sampling design. There were distinct sex differences in the results. In girls, lung function was lowest among active asthmatics taking prescription respiratory medicine, whereas lung function in other active and inactive asthmatics did not differ greatly from that in nonasthmatics. In boys, however, all groups of asthmatics had substantially lower lung function than nonasthmatics. Differences in lung function between active asthmatics and nonasthmatics were stable with increasing age. However, the lung function of inactive asthmatic girls and boys returned to and diverged from nonasthmatics' levels, respectively. In asthmatic girls, passive smoking was associated with reduced lung function; having a dog or cat was associated with increased lung function; and gas stove use was associated with reduced lung function among subjects not taking prescription respiratory medicine.

Adolescent↗
PubMed2006

Optimizing occupational exposure measurement strategies when estimating the log-scale arithmetic mean value--an example from the reinforced plastics industry.

When assessing occupational exposures, repeated measurements are in most cases required. Repeated measurements are more resource intensive than a single measurement, so careful planning of the measurement strategy is necessary to assure that resources are spent wisely. The optimal strategy depends on the objectives of the measurements. Here, two different models of random effects analysis of variance (ANOVA) are proposed for the optimization of measurement strategies by the minimization of the variance of the estimated log-transformed arithmetic mean value of a worker group, i.e. the strategies are optimized for precise estimation of that value. The first model is a one-way random effects ANOVA model. For that model it is shown that the best precision in the estimated mean value is always obtained by including as many workers as possible in the sample while restricting the number of replicates to two or at most three regardless of the size of the variance components. The second model introduces the 'shared temporal variation' which accounts for those random temporal fluctuations of the exposure that the workers have in common. It is shown for that model that the optimal sample allocation depends on the relative sizes of the between-worker component and the shared temporal component, so that if the between-worker component is larger than the shared temporal component more workers should be included in the sample and vice versa. The results are illustrated graphically with an example from the reinforced plastics industry. If there exists a shared temporal variation at a workplace, that variability needs to be accounted for in the sampling design and the more complex model is recommended.

Air Pollutants, Occupational↗
PubMed2004

BAPS 2: enhanced possibilities for the analysis of genetic population structure.

UNLABELLED: Bayesian statistical methods based on simulation techniques have recently been shown to provide powerful tools for the analysis of genetic population structure. We have previously developed a Markov chain Monte Carlo (MCMC) algorithm for characterizing genetically divergent groups based on molecular markers and geographical sampling design of the dataset. However, for large-scale datasets such algorithms may get stuck to local maxima in the parameter space. Therefore, we have modified our earlier algorithm to support multiple parallel MCMC chains, with enhanced features that enable considerably faster and more reliable estimation compared to the earlier version of the algorithm. We consider also a hierarchical tree representation, from which a Bayesian model-averaged structure estimate can be extracted. The algorithm is implemented in a computer program that features a user-friendly interface and built-in graphics. The enhanced features are illustrated by analyses of simulated data and an extensive human molecular dataset. AVAILABILITY: Freely available at http://www.rni.helsinki.fi/~jic/bapspage.html.

Algorithms↗
PubMed2005

A brief case-finding questionnaire for common mental disorders: the CMDQ.

OBJECTIVES: The aim of the study was to validate a new case-finding instrument for common mental disorders (CMDQ). METHODS: A cross-sectional, stratified, two-phase study was carried out in 28 general practices in Aarhus County, Denmark. 1785 consecutive patients, 18-65 years old, consulting 38 GPs with a new health problem participated. Patients were screened before consultation using a one-page screening questionnaire including subscales for somatisation (SCL-SOM and Whiteley-7), anxiety (SCL-ANX4), depression (SCL-DEP6) and alcohol abuse (CAGE). A stratified subsample of 701 patients was interviewed using the Schedules for Clinical Assessment in Neuropsychiatry (SCAN) interview. We tested the external validity of the scales using the SCAN interview as gold standard. All data were analysed using appropriate weighted procedures to control for the two-phase sampling design and non-response bias. RESULTS: Estimates of sensitivity and specificity for relevant ICD-10 diagnoses at theoretical optimal cut-off points on subscales: Depressive disorder: 78/86 (SCL-DEP6); Alcohol abuse or dependence: 78/97 (CAGE); Severe anxiety disorder: 77/85 (SCL-ANX4); Somatisation disorder: 83/56 (SCL-SOM); and 75/52 (Whiteley-7); any mental disorder: 72/72 (SCL-8). At the theoretical optimal cut-off points the CMDQ demonstrated higher diagnostic accuracy than GPs on any diagnosis evaluated. CONCLUSION: The study results suggest that the CMDQ has excellent external validity for use as a diagnostic aid in primary care settings.

Adolescent↗
PubMed1995

Separating population structure from population history: a cladistic analysis of the geographical distribution of mitochondrial DNA haplotypes in the tiger salamander, Ambystoma tigrinum.

Nonrandom associations of alleles or haplotypes with geographical location can arise from restricted gene flow, historical events (fragmentation, range expansion, colonization), or any mixture of these factors. In this paper, we show how a nested cladistic analysis of geographical distances can be used to test the null hypothesis of no geographical association of haplotypes, test the hypothesis that significant associations are due to restricted gene flow, and identify patterns of significant association that are due to historical events. In this last case, criteria are given to discriminate among contiguous range expansion, long-distance colonization, and population fragmentation. The ability to make these discriminations depends critically upon an adequate geographical sampling design. These points are illustrated with a worked example: mitochondrial DNA haplotypes in the salamander Ambystoma tigrinum. For this example, prior information exists about restricted gene flow and likely historical events, and the nested cladistic analyses were completely concordant with this prior information. This concordance establishes the plausibility of this nested cladistic approach, but much future work will be necessary to demonstrate robustness and to explore the power and accuracy of this procedure.

Ambystoma↗
PubMed1996

Microsatellites and the genetics of highly selfing populations in the freshwater snail Bulinus truncatus.

Hermaphrodite tropical freshwater snails provide a good opportunity to study the effects of mating system and genetic drift on population genetic structure because they are self-fertile and they occupy transient patchily distributed habitats (ponds). Up to now the lack of detectable allozyme polymorphism prevented any intrapopulation studies. In this paper, we examine the consequences of selfing and bottlenecks on genetic polymorphism using microsatellite markers in 14 natural populations (under a hierarchical sampling design) of the hermaphrodite freshwater snail Bulinus truncatus. These population genetics data allowed us to discuss the currently available mutation models for microsatellite sequences. Microsatellite markers revealed an unexpectedly high levels of genetic variation with < or = 41 alleles for one locus and gene diversity of 0.20-0.75 among populations. The values of any estimator of Fis indicate high selfing rates in all populations. Linkage disequilibria observed at all loci for some populations may also indicate high levels of inbreeding. The large extent of genetic differentiation measured by Fst, Rst or by a test for homogeneity between genic distributions is explained by both selfing and bottlenecks. Despite a limited gene flow, migration events could be detected when comparing different populations within ponds.

Animals↗
PubMed2003

Bayesian analysis of genetic differentiation between populations.

We introduce a Bayesian method for estimating hidden population substructure using multilocus molecular markers and geographical information provided by the sampling design. The joint posterior distribution of the substructure and allele frequencies of the respective populations is available in an analytical form when the number of populations is small, whereas an approximation based on a Markov chain Monte Carlo simulation approach can be obtained for a moderate or large number of populations. Using the joint posterior distribution, posteriors can also be derived for any evolutionary population parameters, such as the traditional fixation indices. A major advantage compared to most earlier methods is that the number of populations is treated here as an unknown parameter. What is traditionally considered as two genetically distinct populations, either recently founded or connected by considerable gene flow, is here considered as one panmictic population with a certain probability based on marker data and prior information. Analyses of previously published data on the Moroccan argan tree (Argania spinosa) and of simulated data sets suggest that our method is capable of estimating a population substructure, while not artificially enforcing a substructure when it does not exist. The software (BAPS) used for the computations is freely available from http://www.rni.helsinki.fi/~mjs.

Bayes Theorem↗
PubMed2002

Low cognitive performance, comorbid disease, and task-specific disability: findings from a nationally representative survey.

BACKGROUND: This research evaluated the association of low cognitive performance with both chronic diseases and conditions, and with difficulties in a broad array of task-specific functioning and disability measures in older adults living in the community. METHODS: Data were from the first wave of the Assets and Health Dynamics Among the Oldest-Old Study, a national panel survey of individuals age 70 and older (n = 6600 age-eligible self-respondents). Low cognitive performance (LCP) was defined as scores in the lowest (poorest performing) 25th percentile of a cognitive performance scale. The associations of LCP with prevalent chronic diseases and conditions and with limitations in 14 tasks (strength and mobility, instrumental activities of daily living, and activities of daily living) were evaluated. Associations of LCP and task limitations were adjusted for potential modifiers and confounders, including demographic characteristics (age, gender, race), educational attainment, chronic diseases, depressive symptoms, and sensory impairments. Data were weighted to account for complex sample design and nonresponse. RESULTS: More than one third of people with LCP had three or more coexisting diseases and conditions. The unadjusted associations of LCP with task functioning were attenuated after covariate adjustment, but even after adjustment, LCP remained significantly and independently associated with functioning problems in 9 of 14 tasks (borderline with four more), including mobility tasks. CONCLUSIONS: Low cognitive performance, regardless of its relationship to clinical dementia, coexists with multiple chronic diseases and conditions. It is independently associated with a broad array of functioning difficulties, even after controlling for demographic characteristics, educational attainment, and chronic conditions. Chronic diseases and conditions, however, attenuate the relationship between LCP and some task difficulties. LCP should be considered an important comorbid condition associated with both chronic diseases and disability that substantially increases the health burden of many older adults who are poorly equipped to handle it.

Activities of Daily Living↗
PubMed1997

Predicting mortality from community surveys of older adults: the importance of self-rated functional ability.

Using data from the 1990 baseline of the National Survey of Self-Care and Aging (NSSCA), and nearly three years of follow-up mortality data, we examined the association between self-rated functional ability, a global measure of perceived ability of function independently, and mortality among a national sample of older adults. The study included 3,485 subjects selected from the Medicare Beneficiary Files according to a stratified random sampling design, with approximately equal numbers of adults by gender in each of three age categories, 65-74, 75-84, and 85 and over. Self-rated functional ability was found to have an independent contribution to the subsequent risk of death among older adults. Using multivariate models that accounted for self-rated health, age, gender, medical conditions, functional status, and assistance from others, poor self-ratings on this single item nearly doubled the risk of death during the follow-up period. These findings suggest the importance, for both researchers and clinicians, of measuring the potential prognostic importance of self-ratings of health and self-ratings of functional ability among older adults.

Activities of Daily Living↗
PubMed2001

Social support and caregiver distress: a replication analysis.

OBJECTIVES: Prior studies have conceptualized and operationalized social support in different ways, making it difficult to determine if the inconsistencies in findings are due to differences in study design, samples, conceptualization, or measurement. The present study examined the replicability of models of social support and caregiver distress across 4 community-based caregiving studies representative of many conducted in the past 10 years. The goal was to identify areas of consistency in findings across the data sets. METHODS: The authors analyzed 3 models specifying patterns of relationship between social support and depression (main effect, mediation effect, and moderation effect) separately within data sets using hierarchical ordinary least squares regression. Results were compared across data sets. RESULTS: The replication analysis confirmed the robustness of behavior problems and caregiver health as important contributors to caregiver distress. Results of hypotheses examining the pattern of relationship between social support and distress were inconsistent, however. Only 1 type of social support was associated with distress in the expected direction: Less emotional support was associated with higher levels of distress in 2 of the 4 data sets. DISCUSSION: More complex theoretical models that incorporate common measures to represent the linkages between types of stressor, types of support, and their interactions are needed to foster replicability and generalizability of research results.

Adult↗
PubMed2006

Obligations to stepparents acquired in later life: relationship quality and acuity of needs.

OBJECTIVE: . The purpose of this study was to examine beliefs about responsibilities of an adult child to an older stepparent or parent who has remarried later in life. We also investigated the effects of relationship quality and acuity of needs on perceived responsibilities to parents and stepparents. METHODS: We obtained a sample of 487 men and 571 women from across the United States by using a multistage probability sampling design that used random-digit dialing of telephone numbers. We presented respondents with a multiple-segment vignette in which the type of relationship between the adults (i.e., parent-child or stepparent-stepchild), the relationship quality, and the acuity of the older person's need were randomly varied. Respondents indicated how much help the younger adult should give the older person and how obligated the younger adult was to help the older person. In addition, we asked respondents open-ended questions about the rationale for their judgments about intergenerational helping. RESULTS: Perceived responsibilities to parents were greater than responsibilities to stepparents. Relationship quality and acuity of need were also related to obligation beliefs. DISCUSSION: Stepparents acquired later in life generally are not seen as family members, and thus norms of family obligations do not apply to them.

Adolescent↗
PubMed1989

Cognitive impairment among elderly adults in Shanghai, China.

This study reports the methods and initial findings of the first longitudinal study of Alzheimer's disease and dementia in China. A probability sample of 5,055 noninstitutionalized elderly persons in Shanghai was tested directly during the first phase of the study using a Chinese version of the Mini-Mental State Examination (MMSE). Details of sampling design and data collection procedures are described. Overall, some 4.1 percent of adults 55 years or older may be classified as having severe cognitive impairment, and 14.4 percent are mild cases. The rates for females are higher than for males by a ratio of 3.75 in the severe category, and 2.6 in the mild group. Within each age group, cognitive impairment rates vary by education. Multiple logistic regression was used to examine, within each age group, the nature of the association between the presence of a cognitive impairment and educational level controlling for sex. The results showed that educational attainment has a highly significant inverse relationship with prevalence of cognitive impairments (severe vs others). On the other hand, when educational attainment was controlled for in the logistic regression model, sex was significantly associated with prevalence of cognitive disorders for the age groups 65-74 and 75 years or older, but not for the group 55-64 years. These findings suggest the impact that basic educational deficits have on human cognitive functioning as measured through tests like the MMSE. Cross-tabulations of impairment rates according to marital status, economic status, and health-related problems are also presented.

Activities of Daily Living↗
PubMed1991

Health perceptions and survival: do global evaluations of health status really predict mortality?

Self-evaluations of health status have been shown to predict mortality, above and beyond the contribution to prediction made by indices based on the presence of health problems, physical disability, and biological or life-style risk factors. Several possible reasons for this association are discussed: (a) methodological shortcomings of previous studies render the association spurious; (b) other psychosocial influences on mortality are involved and explain the association; and (c) self-evaluations of health status have a direct and independent effect of their own. Four-year follow-up mortality data from the Yale Health and Aging Project (N = 2812) are used to explore these possibilities. The analysis controls for the contribution of numerous indicators of health problems, disability and risk factors, and also makes adjustments of standard errors for the complex sample design. The findings favor the third possibility, an independent effect, to the extent that the particular set of psychosocial factors examined did not explain the basic association, and to the extent that the control variables were an adequately comprehensive set.

Activities of Daily Living↗
PubMed1997

Gain in the caregiving experience: where are we? What next?

This critical review of 29 studies published through 1996 on the gain experienced among informal caregivers of older adults, identifies 13 conceptual (i.e., definitions and theoretical frameworks) and methodological (i.e., sampling, design, measurement, analysis) observations. Key limitations of prior research are highlighted and recommendations necessary for the advancement of research in this area of inquiry are made. Drawing upon relevant theoretical frameworks and the observations noted in this review, a conceptual framework is proposed to bring some consistency to the ways in which future research on positive aspects of caregiving proceeds.

Adaptation, Psychological↗
PubMed1998

Smoking and female infertility: a systematic review and meta-analysis.

The high prevalence of smoking among women in their reproductive years continues to be a matter of concern. The negative effects of smoking on general health are well known, but smoking may also affect fertility. The objective of the present study was to perform a systematic review of the literature to determine whether there is an association between smoking and risk of infertility in women of reproductive age, and to assess the size of this effect. In the 12 studies used for this meta-analysis, the overall value of the odds ratio (OR) for risk of infertility in women smokers versus non-smokers was 1.60 [95% confidence interval (CI) 1.34-1.91]. Studies of subfertile women undergoing in-vitro fertilization (IVF) treatment also show a reduction in fecundity among women smokers. A meta-analysis of nine studies found an OR of 0.66 (95% CI 0.49-0.88) for pregnancies per number of IVF-treated cycles in smokers versus non-smokers. Despite the potential limitations of meta-analyses of observational studies, the evidence presented in this review is compelling because of the consistency of effect across different study designs, sample size and types of outcome. However, continued reassurance is needed that the calculated overall effect is not in fact due to confounding variables.

Adult↗
PubMed1998

Health status of Persian Gulf War veterans: self-reported symptoms, environmental exposures and the effect of stress.

BACKGROUND: Most US troops returned home from the Persian Gulf War (PGW) by Spring 1991 and many began reporting increased health symptoms and medical problems soon after. This investigation examines the relationships between several Gulf-service environmental exposures and health symptom reporting, and the role of traumatic psychological stress on the exposure-health symptom relationships. METHODS: Stratified, random samples of two cohorts of PGW veterans, from the New England area (n = 220) and from the New Orleans area (n = 71), were selected from larger cohorts being followed longitudinally since arrival home from the Gulf. A group of PGW-era veterans deployed to Germany (n = 50) served as a comparison group. The study protocol included questionnaires, a neuropsychological test battery, an environmental interview, and psychological diagnostic interviews. This report focuses on self-reported health symptoms and exposures of participants who completed a 52-item health symptom checklist and a checklist of environmental exposures. RESULTS: The prevalence of reported symptoms was greater in both Persian Gulf-deployed cohorts compared to the Germany cohort. Analyses of the body-system symptom scores (BSS), weighted to account for sampling design, and adjusted by age, sex, and education, indicated that Persian Gulf-deployed veterans were more likely to report neurological, pulmonary, gastrointestinal, cardiac, dermatological, musculoskeletal, psychological and neuropsychological system symptoms than Germany veterans. Using a priori hypotheses about the toxicant effects of exposure to specific toxicants, the relationships between self-reported exposures and body-system symptom groupings were examined through multiple regression analyses, controlling for war-zone exposure and post-traumatic stress disorder (PTSD). Self-reported exposures to pesticides, debris from Scuds, chemical and biological warfare (CBW) agents, and smoke from tent heaters each were significantly related to increased reporting of specific predicted BSS groupings. CONCLUSIONS: Veterans deployed to the Persian Gulf have higher self-reported prevalence of health symptoms compared to PGW veterans who were deployed only as far as Germany. Several Gulf-service environmental exposures are associated with increased health symptom reporting involving predicted body-systems, after adjusting for war-zone stressor exposures and PTSD.

Adult↗