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D Commenges

Publications and source records attributed to D Commenges.

At least 19 recordsLinked to original sources
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↗
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↗
PubMed1996

A proportional hazards model for arbitrarily censored and truncated data.

Turnbull (1976, Journal of Royal Statistical Society, Series B 38, 290-295) proposed a method for nonparametric estimation of the distribution function when the data are incomplete because of censoring and truncation. However, as noted by Frydman (1994, Journal of Royal Statistical society, Series B 56, 71-74), Turnbull's method has to be modified to accommodate both truncation and censoring. This paper presents a detailed correction of Turnbull's method and an extension to the regression analysis: a method of fitting the proportional hazards model for arbitrarily censored and truncated data is developed. The method allows partial testing for zero regression coefficients. The test can be performed using the likelihood ratio test or the Wald test. The methodology is applied to estimate the distribution of the induction time of patients diagnosed with transfusion-associated AIDS and to estimate the distribution of time from diabetes onset to development of diabetic nephropathy for insulin-dependent diabetics.

Acquired Immunodeficiency Syndrome↗
PubMed1995

A direct approach for correcting AIDS incidence: variance formula and comparison with other methods.

We present a direct approach for correcting the acquired immunodeficiency syndrome (AIDS) incidence data for reporting delays, based on a non-parametric method for the analysis of right truncated data. We show that the proposed method when applied for grouped data is equivalent to three other published methods. We give a simple formula for the variance of the estimated AIDS incidence. Both estimator and variance are assessed in a simulation study. It is important for the estimation of AIDS incidence in the last quarter of the period under consideration to use month rather than quarter or half-year as the time unit for the analyses. The method is illustrated using data from the United States Centers for Disease Control.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Development of the WPC approach and application to linkage analysis of breast cancer.

We develop the weighted pairwise correlation approach in several directions: we use a method based on martingale residuals rather than rank residuals; we give a measure of the strength of the linkage and we propose a method for multipoint analysis by combining the weights used in the statistics for different markers. These tools are applied to 214 breast cancer families. The values of the test statistics for the different markers are very similar to those obtained with the lod-score approach; the multipoint analysis increases the value of the test statistic and is also in agreement with previous results.

Breast Neoplasms↗
PubMed1995

Visuo-spatial attention and psychomotor performance in elderly community residents: effects of age, gender, and education.

In cross-sectional analysis of 1,799 subjects of the Paquid Research Program, an epidemiological study on brain aging conducted in the Bordeaux area (France), we have studied the effects of age, gender, and education level on psychometric tests requiring visuo-spatial focused attention and psychomotor performance. Although previous studies suggest that normal aging produces no significant change in focused attention, we did observe lower attentional abilities and lower speed of execution with increasing age. Female gender and low education level were also related to poorer attention and psychomotor performance. As the effects of these individual factors are difficult to disentangle from each other on the small samples of subjects used in group studies, epidemiological surveys seem useful to provide a better understanding of the neuropsychology of aging.

Age Factors↗
PubMed1995

Social and leisure activities and risk of dementia: a prospective longitudinal study.

OBJECTIVE: To study the relationship between social and leisure activities and risk of subsequent dementia in older community residents. SETTING: A cohort study of people aged 65 and older were followed-up 1 and 3 years after a baseline screening (the Paquid study). PARTICIPANTS: 2040 older subjects living at home in Gironde (France) were randomly selected and followed for at least 3 years. DATA COLLECTION: Information about social and leisure activities was collected during the baseline screening with an interview by a psychologist. Incident cases of dementia were detected during the first and third year follow-up screenings according to the DSM-III-R criteria. MAIN RESULTS: All but one of the social and leisure activities noted were significantly associated with a lower risk of dementia. Only golden club participation was not significantly associated with this risk. After adjustment for age and cognitive performance measured by the Mini-Mental State Exam, visual memory test, and verbal fluency test, only traveling (Relative risk (RR) = .48,95% Confidence Interval (95% CI) = .24-.94), odd jobs or knitting (RR = .46,95% CI = .26-.85), and gardening (RR = .53, 95% CI = .28-.99) remained significant. CONCLUSIONS: Regular participation in social or leisure activities such as traveling, odd jobs, knitting, or gardening were associated with a lower risk of subsequent dementia.

Aged↗
PubMed1995

Score test for familial aggregation in probands studies: application to Alzheimer's disease.

When studying familial aggregation of a disease, the following two-stage design is often used: first select index subjects (cases and controls); then record data on their relatives. The likelihood corresponding to this design is derived and a score test of homogeneity is proposed for testing the hypothesis of no-aggregation. This test takes into account the selection procedure and allows adjustment to be made for explanatory variables. It appears as the sum of three terms: a pure test of homogeneity, a test of comparison of observed minus expected cases in the two groups, and a term which adjusts for the possible unequal probabilities of disease of the index subjects. Asymptotic efficiency and a simulation study show that the proposed test is superior to either the pure homogeneity test or tests based on the comparison of numbers of affected in the two groups. The test statistic, which has an asymptotically standard normal distribution, is applied to a study of familial aggregation of early-onset Alzheimer's disease for which a highly significant value (9.46) is obtained: this is the highest value among the three tests compared, in agreement with the simulation study. A logistic normal model is fitted to the data, taking account of the selection procedure: it allows to estimate the regression parameters and the variance of the random effect; the likelihood ratio test for familial aggregation seems less powerful than the score test.

Alzheimer Disease↗
PubMed1994

Components of drinking water and risk of cognitive impairment in the elderly.

The relation between aluminum, fluorine, calcium, and pH in drinking water and the risk for cognitive impairment was studied using data collected in 1988-1989 in a population-based survey of 3,777 French men and women aged 65 years and older (the Paquid study). Cognitive impairment was defined as a score lower than 24 on the Mini-Mental State Examination. Data related to drinking water came from two prospective measurement surveys whose reliability was checked by a variability study. A mixed effects logistic regression was performed, adjusting for the effects of the age, sex, educational level, and occupation of the participants. A significant protective effect was found for high calcium concentration (odds ratio = 0.8 for a concentration > or = 75 mg vs. < 75 mg, p = 0.015). For aluminum, no significant effect was found when pH was not included in the model, but the results showed a weak interaction between aluminum and pH. When the four variables (calcium, aluminum, pH, and aluminum x pH interaction) were considered in the statistical analysis as a group, this group was significantly related to cognitive impairment (p = 0.01).

Aged↗
PubMed1994

Robust genetic linkage analysis based on a score test of homogeneity: the weighted pairwise correlation statistic.

In testing genetic linkage using large or complex pedigrees, robust methods may be preferred to the Lod-score method. The affected-pedigree-member method is robust but does not use the information available in nonaffected subjects, which results in a loss of power. We propose a new test of genetic linkage based on a score test of homogeneity derived from a random effect model. The statistic is simple and uses only pairs of subjects. In contrast with the affected-pedigree-method, it uses all the available pairs and does not depend on the marker alleles frequencies. A rank version of this weighted pairwise correlation statistic is proposed, its exact first and second moment derived. We show that for age-dependent diseases, it provides a simple nonparametric test.

Age of Onset↗
PubMed1994

The weighted rank pairwise correlation statistic for linkage analysis: simulation study and application to Alzheimer's disease.

The weighted rank pairwise correlation (WRPC) statistic has been proposed as a robust test of genetic linkage, particularly adapted to the analysis of large and complex pedigrees and for age-dependent and heterogeneous diseases. In this paper a simulation study is presented. Validity and power of the WRPC test are studied and compared to the Haseman-Elston sibpair method for various types of problems. The power of the WRPC test is slightly lower than the Haseman-Elston method for analyzing a large number of small randomly chosen pedigrees. It is higher however in presence of genetic heterogeneity or for analyzing large individual pedigrees. Recently, evidence of linkage of Alzheimer's disease with a locus on chromosome 14, D14s43, has been obtained by the Lod-score method. We reanalyze these data using the WRPC test, essentially confirming the results of the Lod-score method. The WRPC test statistic is higher than the equivalent Lod-score statistic for the two pedigrees which show strong evidence of linkage with the two methods. The global WRPC test statistic is slightly lower than the Lod-score test statistic. The WRPC test, however, makes no hypothesis of a specific genetic transmission model and can be computed very quickly; in addition, an exact P-value can be computed by simulation for individual pedigrees.

Alzheimer Disease↗
PubMed1994

Tobacco consumption and cognitive impairment in elderly people. A population-based study.

We examined the relationship between tobacco consumption and Alzheimer's disease (AD), cognitive deficit, and memory performances in elderly community residents of southwestern France. Subjects were considered to have a cognitive deficit if they scored under 24 on the French version of the Mini-Mental State Examination, and poor memory performances if they scored under 8 on the Benton Visual Retention Test. Among the 3770 subjects who gave information about their smoking habits, only 356 (9.5%) were current smokers, 998 (26.5%) were past smokers, and 2416 (64%) were never smokers. Current smokers (odds ratio (OR) = 0.52, P < 0.001) and past smokers (OR = 0.54, P < 0.001) had a lower risk of cognitive deficit than did never smokers. However, this significant relationship disappeared after adjustment for potential confounding factors such as occupational category (OR = 0.91 (not significant) for current smokers and OR = 0.87 (not significant) for past smokers). Similar results were obtained for the risk of AD and of poor memory performances. The apparent protective effect of smoking habits on cognitive abilities could be due to a confounding effect of occupational category.

Aged↗
PubMed1994

Incidence of dementia and Alzheimer's disease in elderly community residents of south-western France.

BACKGROUND: Dementia is a growing problem in developed countries. The aim of this paper is to estimate incidence rates of dementia, Alzheimer's disease and vascular dementia in a community population of South-Western France. METHODS: A sample of 2792 subjects was selected and followed-up 1 year and 3 after the initial screening. At each visit, a standardized questionnaire was administered by trained psychologists. Demented subjects were identified using a two-step procedure. The first step consisted of a systematic screening by the psychologist using DSM IIIR criteria for dementia. In the second step, subjects who fulfilled the DSM IIIR criteria were examined by a neurologist. NINCDS-ADRDA criteria were applied to diagnose Alzheimer's disease. RESULTS: Incidences of dementia and Alzheimer's disease were estimated at 16.3 and 11.4 per 1000 per year, respectively. Incidence estimates increased with age from 2 per 1000 in subjects aged 65-69 years to 74 per 1000 in subjects > 90 years. Incidence estimates of Alzheimer's disease showed the same increased from 0.7 per 1000 to 66 per 1000. Incidences of dementia and of Alzheimer's disease did not level off with age and were not different between genders.

Aged↗
PubMed1994

Test of homogeneity of binary data with explanatory variables.

Apparent heterogeneity of the risk of a disease in different groups may be explained by subject-specific risk factors unequally distributed in these groups. We propose a score test of homogeneity that allows adjustment for known risk factors of the disease. The test is based on a random-effect logistic regression model and requires only simple computations in addition to a conventional logistic regression method. The score test is applied to the study of geographical heterogeneity of cognitive impairment in elderly using a sample of 3,318 subjects scattered in 75 parishes. It is shown that an apparent heterogeneity disappears when taking into account subject-specific risk factors. This test may also be useful for studying familial aggregation of a disease.

Epidemiologic Methods↗
PubMed1994

The intraclass correlation coefficient: distribution-free definition and test.

A definition of the intraclass correlation coefficient is given on the basis of a general class of random effect model. The conventional intraclass correlation coefficient and the intracluster correlation coefficient for binary data are both particular cases of the generalized coefficient. We derive the score test for the hypothesis of null intraclass correlation in the exponential family. The statistic does not depend on the particular distribution in this family and is related to the pairwise correlation coefficient. The test can be adjusted for explanatory variables.

Aged↗