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D Commenges

Publications and source records attributed to D Commenges.

At least 37 records · Page 2Linked to original sources
PubMed1998

Illustration of analysis taking into account complex survey considerations: the association between wine consumption and dementia in the PAQUID study. Personnes Ages Quid.

Epidemiologists are increasingly looking to large-scale sample surveys to provide data for studies of the associations between known or suspected risk factors and disease. More often than not, widely available statistical software packages have been used to analyze such data, particularly when multivariable modeling is involved. Such packages assume that the data have resulted from simple random samples. However, when the survey design incorporates such features as clustering and stratification, the results of statistical analyses based on this assumption can be incorrect. The authors utilized data from the PAQUID (Personnes Agees Quid) study, collected periodically from 1988 to 1996, to illustrate the ease of performing a "design-based" (vs. a "model-based") analysis of complex survey data, and they compared the results obtained using both approaches. The PAQUID study is a stratified cluster sample of elderly community residents in the southwestern departments of Gironde and Dordogne, France. In the illustration presented-in which 3,777 community residents aged 65 years or older were selected to permit identification of baseline and lifetime factors that might be related to cognitive loss, dementia, and Alzheimer's disease--measures of association (such as odds ratios and their associated standard errors) were comparable for both analytical strategies. However, this may not be the case for other examples. Descriptive measures (such as estimates of means and proportions) may be more seriously compromised by the decision to ignore the sampling design. The availability of modern statistical packages with survey analysis capabilities should encourage data analysts to perform design-based analyses whenever possible.

Aged↗
PubMed1998

Cognitive process in preclinical phase of dementia.

Several recent prospective studies have demonstrated the existence of a preclinical stage of dementia, identifiable by neuropsychological assessment showing impairments with a great variety of cognitive tests. However, test scores are often colinear, largely because common cognitive components are involved in different tests; in spite of an apparent heterogeneity, it is still possible that a common cognitive component may be responsible for the deterioration shown in different tests in the preclinical phase. We studied the cognitive performances of 1159 elderly residents in the PAQUID (Personnes Agées quid) cohort, at a fixed lag time of 2 years before the clinical diagnosis of dementia. Seven neuropsychological tests were administered (Mini-Mental Status Examination, Benton Visual Retention Test, Wechsler Paired-Associates Test, Isaacs Set Test, Zazzo's Cancellation Task, Digit Symbol Substitution Test and Wechsler Similarities Test). Among the initially non-demented 1159 subjects, 25 developed a dementia 2 years later, of whom 16 were classified as cases of Alzheimer's disease. In order to dissect the multicolinearity of the tests we used a multivariate approach with principal component analysis (PCA). The patients' loading on each of the first four PCA factors were subsequently correlated with the risk of dementia and Alzheimer's disease 2 years later. The logistic regression with backward stepwise selected only the first factor as an independent predictor of dementia or Alzheimer's disease. Analysis shows that there are good reasons to suspect that the first PCA factor represents a general factor corresponding to aspects of control in the tasks used. Our results therefore seem to show that preclinical deficits in dementia and Alzheimer's disease reflect the deterioration of a general cognitive factor, which may be interpreted as the disturbance of central, control processes.

Aged↗
PubMed1998

Modelling of the probability of success of the stages of in-vitro fertilization and embryo transfer: stimulation, fertilization and implantation.

The aim of this study was to find the factors explaining the probability of success of in-vitro fertilization (IVF)-embryo transfer and its different stages: stimulation, fertilization and implantation. The sample came from a retrospective cohort followed in the IVF-embryo transfer centre of the Centre Hospitalier Universitaire of Pellegrin, Bordeaux, France; the data from 471 couples giving rise to 923 IVF-embryo transfer cycles were recorded. Four logistic regression models were specified for global process, stimulation, fertilization and implantation stages. Random effect models were used for taking into account the correlations of the different cycles for the same woman. The main outcome measures were: ongoing pregnancy, number of oocytes, number of embryos. A total of 135 ongoing pregnancies was observed. The significant explanatory variables were for global process: age [> or = 38 years: odds ratio (OR) = 0.28], donor sperm IVF-embryo transfer (OR = 2.1), number of ampoules (OR = 0.98), previous IVF-embryo transfer livebirth (OR = 2.36); for stimulation: age (> or = 35 years: OR = 0.38) and number of days of treatment > 13 days (OR = 0.20); for fertilization: accident during previous IVF-embryo transfer gestation (OR = 0.39), absolute tubal infertility (OR = 1.38) and the number of ampoules of human menopausal gonadotrophin (HMG) per day (OR = 0.85); for implantation: age (age > or = 38 years: OR = 0.34), donor sperm IVF-embryo transfer (OR = 4.58), number of ampoules (OR = 0.98), number and quality of the embryos. Estimates of the probabilities of success are also given for the global process.

Adult↗
PubMed1998

A penalized likelihood approach for arbitrarily censored and truncated data: application to age-specific incidence of dementia.

The Cos model is the model of choice when analyzing survival data presenting only right censoring and left truncation. There is a need for methods that can accommodate more complex observation schemes involving general censoring and truncation. In addition, it is important in many epidemiological applications to have a smooth estimate of the hazard function. We show that the penalized likelihood approach gives a solution to these problems. The solution of the maximum of the penalized likelihood is approximated on a basis of splines. The smoothing parameter is estimated using approximate cross-validation; confidence bands can be given. A simulation study shows that this approach gives better results than the smoothed Nelson-Aalen estimator. We apply this method to the analysis of data from a large cohort study on cerebral aging. The age-specific incidence of dementia is estimated and risk factors of dementia studied.

Age Factors↗
PubMed1998

Risk factors for fractures in the elderly.

We report the results of a 5-year prospective cohort study of risk factors for fractures, including drinking fluoridated water, in a cohort of 3,216 men and women aged 65 years and older. We studied risk factors for hip fracture and fractures at other locations separately. We found a higher risk of hip fractures for subjects exposed to fluorine concentrations over 0.11 mg per liter but without a dose-effect relation (odds ratio (OR) = 3.25 for a concentration of 0.11-0.25 mg per liter; OR = 2.43 for > or = 0.25 mg per liter]. For higher thresholds (0.7 and 1 mg per liter), however, the OR was less than 1. We found no association between fluorine and non-hip fractures. Non-hip fractures were associated with polymedication rather than with specific drug use, whereas fracture was associated with polymedication and use of anxiolytic and antidepressive drugs. Subjects drinking spirits every day were more likely to have hip fractures. Tobacco consumption increased the risk for non-hip fractures.

Age Factors↗
PubMed1998

Effect of gender, age, transmission category, and antiretroviral therapy on the progression of human immunodeficiency virus infection using multistate Markov models. Groupe d'Epidémiologie Clinique du SIDA en Aquitaine.

This article illustrates the use of time-homogeneous Markov models with covariates to estimate the AIDS incubation period distribution from prevalent cohorts and to evaluate the effect of factors such as gender, age, human immunodeficiency virus (HIV) transmission category, and antiretroviral therapy on disease progression. We applied this methodology to the analysis of data from a cohort of 3,027 patients enrolled from a hospital-based surveillance system of HIV infection in the Bordeaux University Hospital and four secondary public hospitals in southwestern France. A total of 998 individuals (33%) progressed to AIDS during a median follow-up period of 34 months. Based on a progressive three-state Markov model, the estimated mean and median incubation periods were 9.1 years [95% confidence interval (CI) = 8.7-9.6] and 7.5 years (95% CI = 7.2-7.9), respectively. Our analyses showed a similar disease progression in men and women; we observed a more rapid progression for older subjects compared with younger ones and for homosexual men compared with heterosexuals, intravenous drug users, and transfusion recipients, who had similar disease progression rates after adjusting for age. The use of antiretroviral therapy appeared to slow disease progression. Moreover, the results indicated that a combination therapy of zidovudine with another antiretroviral drug may be more efficient than zidovudine monotherapy.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Tests of geographical correlation with adjustment for explanatory variables: an application to dyspnoea in the elderly.

We propose a test of correlation of the residuals in generalized linear models which is a generalization of the spatial autocorrelation test based on Moran's I. It allows adjustment for sizes of geographical areas and for explanatory variables. A formula is given to compute the weights according to the alternative hypothesis. We compare inference using the distribution in the model and using the permutation distribution. A simulation study showed that the model-based test may be very conservative and this leads to a loss of power compared to the permutation test or to the model-based test with correction for estimated parameters. As this latter is intractable for very large samples when the model includes explanatory variables, we recommend the use of the permutation test. The permutation test is used to study geographical correlation of dyspnoea in the elderly.

Age Factors↗
PubMed1997

A 5-year longitudinal study of the Mini-Mental State Examination in normal aging.

The Mini-Mental State Examination (MMSE) measures global cognitive performance and is often used as a screening test for dementia. This paper presents a 5-year longitudinal study of the MMSE score in a sample of 2,537 non-demented French community residents aged 65 years and older who were participants in the Paquid Study in 1988-1992. Subjects were evaluated at the baseline visit (T0) and 1 year (T1), 3 years (T3), and 5 years (T5) later. Analyses performed with a random effects linear model showed that the score rose between T0 and T1 (by 0.60 points for subjects aged 65 years at T0 to 0.83 points for subjects aged 85 years at T0), then it decreased very slightly between T1 and T5 (by 0.02 points for subjects aged 65 years to 0.57 points for subjects aged 85 years). The improvement during the first year, which was larger for less educated subjects, may be explained by the stress due to the test situation at T0 or by a learning effect at T1. The decline during the last 4 years was more pronounced for older and less well educated subjects. The cross-sectional measure of age effect was larger than the longitudinal measure of time effect. This difference may be explained by a cohort effect or by a practice effect induced by repetition of the test. The authors conclude that the MMSE score declines very slightly in non-demented subjects, thus suggesting that the cognitive processes involved are spared by the aging process. These results may have implications for dementia screening.

Aged↗
PubMed1997

WPC test based on randomization for analyzing quantitative traits on simulated pedigrees.

The weighted pairwise correlation (WPC) approach provides simple and flexible tests for genetic linkage which may be adapted to qualitative, quantitative or age-dependent traits. These tests also seem to have good power. However, when working with large pedigrees, a disease susceptibility gene not linked to the marker studied induces correlations of the trait values, leading to inflated type I errors for these tests. We propose here a new approach for inference based on the randomization of the alleles following the Mendelian laws and conditioning on the alleles of the founders. This approach is applied to the analysis of the quantitative traits in a set of simulated pedigrees. The alpha posteriori comparison of the findings to the true model indicates directions for future work.

Aging↗
PubMed1997

Cognitive predictors of dementia in elderly community residents.

Detection of subjects with a high risk of developing dementia is a major goal of epidemiological research. Among the potential predictors, minor cognitive impairments detected by psychometric methods could be important precursors. A total of 2,726 elderly nondemented subjects, aged 65 and over, randomly selected from the general population of Gironde (south-western France) were followed up for 3 years. During this time, 84 developed an incident dementia, diagnosed as Alzheimer's disease (AD) in 59. The relationships between cognitive performance (Mini Mental State Examination, Benton Visual Retention Test and Isaacs Set Test) measured at the baseline screening of the cohort and the risk of dementia or AD were studied with a discrete Cox proportional hazard model. After adjustment for age and educational level, the three test scores remained strongly related to the risk of dementia or AD. Psychometric performance can be used to screen subjects at risk of developing dementia or AD and allow pharmacological intervention at an early stage.

Activities of Daily Living↗
PubMed1997

[Predictive factors for institutionalization in the context of geriatric planning in the Gironde department (France)].

The objective of this study was to investigate the predictive factors over five years follow-up of institutionalization, relevant for starting interventions in the area of Gironde (South Western France). This study deals with a longitudinal study of community residents aged 65 years and older. Of the 2792 subjects initially included in the cohort in year 1988, 2493 were selected for this study, leading to the subjects whose type of housing was known at least once over the five year follow-up (1989-1993). The statistical analysis was made with a discrete Cox proportional hazard model. Of the 2493 subjects, 150 entered an institution during the five years of follow-up, leading to a cumulative incidence of 7.1%. In the multivariate analysis, the predictive factors found in this study were age, absence of phone in the house, living in home for the aged, cognitive decline evaluated with the Mini-Mental-Status-Examination (MMSE), dependency for one item of the Lawton's scale (Instrumental Activities of Daily Living or IADLs), namely the inability to do shopping, and limited social contact with the family. These different indicators are a basis for decision making to target home care services fitted to the needs of the area.

Activities of Daily Living↗
PubMed1997

Wine consumption and dementia in the elderly: a prospective community study in the Bordeaux area.

Alcoholism is a possible cause of dementia, mainly through associated nutritional deficiencies and, rarely, through acute direct toxicity. However alcohol consumption was not found to be a risk factor in previous epidemiologic studies. We prospectively studied 3,777 community residents aged 65 and over, in the districts of Gironde and Dordogne. Average daily alcoholic consumption was recorded at baseline. Incident cases of dementia and Alzheimer's disease were screened at follow-up with explicit criteria. At 3 years, 2,273 subjects not demented at baseline were still available for follow-up. Wine was the only alcoholic beverage reported by more than 95 p. 100 of regular drinkers. In the 318 subjects drinking 3 to 4 standard glasses per day (> 250 and up to 500 ml), categorized as moderate drinkers, the crude odds ratio (OR) was 0.18 for incident dementia (p < 0.01) and 0.25 for Alzheimer's disease (p < 0.03), as compared to the 971 non-drinkers. After adjusting for age, sex, education, occupation, baseline MMSE and other possible confounders, the ORs were respectively 0.19 (p < 0.01) and 0.28 (p < 0.05). In the 922 mild drinkers (< 1 to 2 glasses per day) there was a negative association only with AD, after adjustment (OR = 0.55; p < 0.05). The inverse relationship between moderate wine drinking and incident dementia was explained neither by known predictors of dementia nor by medical, psychological or socio-familial factors. Considering also the well documented negative associations between moderate wine consumption and cardiovascular morbidity and mortality in this age group, it seems that there is no medical rationale to advise people over 65 to quit drinking wine moderately, as this habit carries no specific risk and may even be of some benefit for their health. Advising all elderly people to drink wine regularly for prevention of dementia would be however premature at this stage.

Aged↗
PubMed1997

[Longitudinal study of cognitive aging in non-demented elderly subjects].

BACKGROUND: The aim of this study is to describe and compare the course of the score of two psychometric tests during a five-year period in a cohort of non-demented elderly subjects. We studied a timed test of simple logical reasoning (the Digit Symbol Substitution Test of Wechsler) and a test of short-term visual memory (the Benton Visual Retention Test). Then we compared the course of these two tests with the course of the Mini-Mental State Examination (MMSE) which evaluates the general cognitive functioning and which has been studied previously. METHODS: The sample consisted of 2792 subjects aged 65 years and older living at home at the beginning of the study (the Paquid cohort in Gironde). Subjects were interviewed at home by a psychologist at the baseline visit and one year, 3 years and 5 years after the baseline visit. All subjects who were diagnosed as demented at any of the four examinations were excluded from this study (218 subjects). The statistical analysis was performed using a mixed effects linear model and an additional analysis was performed to study sensitivity of the results to hypotheses regarding missing data mechanism. RESULTS: Among the three tests studied, only the score of the Digit Symbol Substitution Test declined over the five years (by -1.15 points for subjects aged 65 years to -3.4 points for subjects aged 85 years). We observed an improvement of the score between the first two visits which is sharper for the test of Benton and the MMSE than for the Digit Symbol Substitution Test and which reflects a stress effect at the baseline visit or a learning effect at the second visit. The difference between the cross-sectional measure of age effect and the longitudinal measure of time effect suggests either a cohort effect or a practice effect which would persist during the five years. CONCLUSIONS: The cognitive change in a non-demented elderly population is different according to the psychometric test used. Among the three tests studied, only the score of the Digit Symbol Substitution Test which has a a speed component declined over the five years.

Age Factors↗
PubMed1996

Improving the robustness of the weighted pairwise correlation test for linkage analysis.

The weighted pairwise correlation (WPC) approach provides simple and flexible tests for genetic linkage which may be adapted to qualitative, quantitative, or age-dependent traits. These tests also seem to have good power. However, when working with large pedigrees, a disease susceptibility gene not linked to the marker studied induces correlations of the trait values, leading to inflated type-I errors for these tests. Thus, in its first version, the WPC approach is reliable when using sibships but not when using larger pedigrees. We propose a way for correcting the variances of the WPC statistics to take these correlations into account. A simulation study shows that the type I errors of the corrected statistics are good. The approach is based on a transformation which yields uncorrelated residuals. We study three statistics, based on the permutation distributions of residuals: one based on ordinary residuals adapted to quantitative traits, another based on martingale residuals adapted to survival data, and one based on rank residuals which can be used in both situations. We apply the corrected WPC tests to pedigrees of Alzheimer's disease previously analyzed with the first version of the method (WRPC).

Adolescent↗
PubMed1996

Silica and aluminum in drinking water and cognitive impairment in the elderly.

We studied the relation between silica and aluminum levels in drinking water and the risk of cognitive impairment using data from a population-based survey of 3,777 French subjects age 65 years and older. We also studied the effect of pH and the concentrations of calcium, magnesium, fluorine, zinc, copper, and iron. We used a mixed effects logistic regression adjusting for age, sex, educational level, and occupation of the subjects. We confirmed the inverse relation previously found between calcium level and cognitive impairment. We found no important association between cognitive impairment and fluorine, magnesium, iron, copper, or zinc. The association between cognitive impairment and aluminum depended on the pH and the concentration of silica: high levels of aluminum appeared to have a deleterious effect when the silica concentration was low, but there was a protective effect when the pH and the silica level were high. The threshold for an aluminum effect, however, was very low (3.5 micrograms per liter) and did not support the hypothesis of a deleterious effect for only high levels of aluminum.

Aged↗
PubMed1996

Evidence for an age-dependent pyrogenic threshold of Plasmodium falciparum parasitemia in highly endemic populations.

The high prevalence of asymptomatic malaria infections and the nonspecific signs and symptoms of the disease make the individual diagnosis of clinical malaria uncertain in highly endemic areas. Longitudinal data obtained during a four-month period from a daily survey of 200 permanent inhabitants (one month-83 years old) living in a holoendemic area were analyzed in a random-effects logistic regression model to investigate the relationship between the level of Plasmodium falciparum parasitemia and risk of fever. It was not possible to build a model that described/summarized correctly this relationship by a continuous function. Findings provide evidence for an age-dependent threshold effect of parasitemia on the occurrence of fever. The level of this threshold varied by 2.45 trophozoites per leukocyte, maximum at one year of age, to 0.5 trophozoites per leukocyte, minimum at 60 years of age. When the parasite density of a person crossed the threshold level corresponding to his or her age, the individual's risk of fever was multiplied by 44 (95% confidence interval = 13.6-144.8). The existence of this threshold effect allows parasite density to be used to distinguish malaria attacks from other causes of fever within an individual and should facilitate the accurate evaluation of the incidence of clinical malaria in highly endemic areas.

Adolescent↗