Biomedical subjects

D Commenges

Publications and source records attributed to D Commenges.

At least 55 records · Page 3Linked to original sources

PubMed1993

An empirical Bayes approach to the estimation of the incidence curve of HIV infection.

A new approach is proposed for estimating the incidence curve of HIV infection and obtaining short term prediction of AIDS incidence. It is based on the method of back calculation which utilizes the fact that AIDS incidence is generated from HIV infection incidence by convolution with the incubation period distribution, but avoids the difficulties associated with approximating the infection incidence curve by a class of step functions. Instead, the infection incidence is modelled as a simple stochastic epidemic process which ensures smoothness of the estimate. We first derive the distribution of AIDS incidence knowing infection incidence. The best linear estimators of infection incidence as well as future AIDS incidence are given; a smoothed past AIDS incidence is also obtained. The parameters of the stochastic infection process can be estimated by maximum likelihood using a normal approximation to the marginal distribution of the AIDS incidence. This approach is applied to AIDS incidence data in the United States up to mid 1987. We find that the epidemic started in mid 1976, peaked at the end of 1983 and dropped afterwards.

Acquired Immunodeficiency Syndrome↗

PubMed1993

Linkage analysis of Alzheimer's disease with methods using relative pairs.

Four relative-pair methods for detecting genetic linkage were applied to familial Alzheimer's disease data. Results obtained using an extended Haseman-Elston test and a weighted rank pairwise correlation test, which both use information from all relative pairs, were consistent with previously published likelihood results and appear to be more powerful than affected sib pair methods.

Alzheimer Disease↗

PubMed1993

Cerebral and functional aging: first results on prevalence and incidence of the Paquid cohort.

Paquid is an interdisciplinary study designed to investigate cerebral and functional aging. A cohort of 3,777 community residents living in two administrative areas of South-Western France was selected. A standardized questionnaire was administered at home by trained psychologists. The same procedure was applied one and three years after the baseline data collection. The identification of demented subjects was made with a two-step procedure. The first step is a systematic screening by the psychologists using the DSM-III criteria for dementia. Subjects who fulfilled the DSM-III criteria were examined by a neurologist. Diagnosis of dementia is confirmed according to the NINCDS-ADRDA criteria. The Paquid cohort is complemented by a random sample of 357 institutionalized subjects. First results of prevalence and incidence rates show an exponential increase of dementia with age.

Aged↗

PubMed1993

[Prevalence of dementia in Gironde (France)].

The objective of the study is to estimate the prevalence of dementia using the data of the Paquid cohort. A sample of 3,149 subjects aged 65 years and older living at home or in institution was randomly chosen in Gironde (France). A questionnaire and psychometric tests were used to evaluate cognitive functioning and the presence of dementia was assessed through DSM III Diagnostic and Statistical Manual of mental disorders (ed. III) criteria. Hachinski scale and work group NINCDS-ADRDA criteria were applied to confirm the presence of dementia and identify Alzheimer's disease. Overall prevalence was estimated to 4.3%. No difference was found between men and women. The prevalence increased with age with nearly a doubling every 5 years of age. In institution, dementia frequency remained stable. The relative risk of a demented subject to be institutionalized with regard to a non demented subject decreased with age.

Aged↗

PubMed1992

Comparison of the proportions of affected relatives of cases and controls: analysis and minimum sample size formula.

The problem of familial aggregation has frequently been approached by comparing the proportion of affected relatives of index cases with the proportion of affected relatives of index controls. This type of study has an analogy with the case-control design and is frequently analysed as if it was one. It is however an essentially different design which may involve dependent observations. We show that conventional tests for comparing proportions of affected subjects are still valid with this design; we give a formula for computing the minimum sample size required to detect a given degree of aggregation measured by the intracluster correlation coefficient, which can be estimated very simply by the difference in proportions of affected relatives in the two groups.

Case-Control Studies↗

PubMed1992

Principal lifetime occupation and cognitive impairment in a French elderly cohort (Paquid).

The purpose of the present study was to examine the relation between principal lifetime occupation and cognitive performance with the initial data collected (1988-1989) in a cohort of 3,777 community residents of the area of Bordeaux, France, aged 65 years and older. Subjects were considered as cognitively impaired if they scored under 24 on the French version of the mini-mental state examination. Cognitive impairment was found to vary significantly across the different occupational categories. Results of the logistic regression show that age, sex, and educational level are significantly related to cognitive impairment. Moreover, after controlling for these and other covariates, farmworkers (odds ratio (OR) = 6.1, 95% confidence interval (CI) 3.3-11.4), farm managers (OR = 2.9, 95% CI 1.6-5.1), domestic service employees (OR = 2.8, 95% CI 1.5-5.1), and blue-collar workers (OR = 2.5, 95% CI 1.4-4.4) had a higher risk of cognitive impairment than did subjects who had an intellectual occupation. Follow-up of the cohort will permit precise determination of the role of principal lifetime occupation in subsequent cognitive deterioration. Occupational status should be taken into consideration when studying brain aging.

Age Factors↗

PubMed1992

Health measures correlates in a French elderly community population: the PAQUID study.

PAQUID is an epidemiologic prospective study of mental and functional aging. A sample of 4,050 community-dwelling individuals, aged 65 and over, was randomly selected from electoral lists of 37 parishes of Gironde after stratification by age, sex, and size of urban unit; 68.9 percent agreed to participate. Baseline information was obtained from a one-hour home interview. Health measures included ADL, IADL, mobility, Rosow scale, and two subjective health assessments. Depressive symptomatology was assessed by the CES-D scale and cognitive functioning by Folstein's MMS. Dependence rates vary from 9.7 percent to 71.9 percent according to the indicator under consideration. Cross-sectional correlations with dependence are significant for age, sex, education, rural setting, joint pain, dyspnea, hearing and visual impairment, MMS score, and depression. In logistic regressions, only dyspnea, MMS score, and depression are always significantly correlated with dependence, whichever the indicator.

Activities of Daily Living↗

PubMed1992

Improving screening for dementia in the elderly using, Mini-Mental State Examination subscores, Benton's Visual Retention Test, and Isaacs' Set Test.

The Mini-Mental State Examination score is often used as a screening test for dementia. We studied its properties for a population of French community residents, using a sample of 2,792 randomly selected subjects in Gironde, France. When the traditional cutoff point 23-24 was used, we observed a sensitivity of 1.0 and a specificity of 0.77. We sought to increase the specificity of the test, while keeping sensitivity at 1.0, with the use of logistic regression analysis. We found (1) a specificity of 0.81 when "recall three objects" and "orientation to time" were added to the Mini-Mental State Examination score; (2) a specificity of 0.90 when Benton's Visual Retention Tests and Isaacs' Set Test of Verbal Fluency were added to the Mini-Mental State Examination score and subscores; and (3) no improvement in specificity when age and educational level were included in the analyses.

Age Factors↗

PubMed1992

Estimating the incubation period of paediatric AIDS in Rwanda.

OBJECTIVE: To estimate the distribution of the incubation period of paediatric AIDS in Rwanda. DESIGN: Data were collected between February 1984 and December 1990 at the Centre Hospitalier de Kigali (CHK), the capital city of Rwanda, Central Africa. PATIENTS: We used a sample of 685 AIDS cases registered consecutively in the Department of Paediatrics of the CHK, in which the proportion of perinatally acquired HIV-1 infection was estimated to be 98.6%. METHODS: We performed both non-parametric and parametric analyses. The methods of estimation were adapted to truncated data, using essentially the same methods as Auger et al. in their analysis of data from the New York City and the New York State AIDS case registries in 1988. RESULTS: We found that a double Weibull model fitted the data very well and that the risk of developing AIDS was high for subjects under 18 months of age, but lower for older subjects. CONCLUSIONS: Our results were qualitatively similar to those of Auger et al.. There were quantitative differences between the two studies, but it was not possible to compare median survival periods. Parameters such as median or mean survival times cannot be validly estimated using only data from registers because these data exclude infected subjects who have not yet developed AIDS.

Acquired Immunodeficiency Syndrome↗

PubMed1992

Statistical description of the Mini-Mental State Examination for French elderly community residents. Paquid Study Group.

The distribution of total Mini-Mental State Examination (MMSE) scores, individual items, and groups of items were studied in French elderly community residents from a random sample of 2727 subjects. Serial seven, recall three objects, and copy pentagons had the lowest percentage of correct responses, while orientation to place, naming two objects, and three objects registration had the highest percentage of correct responses. The structure of correlation of the items was studied using Principal Components Analysis. The projection of the items on the first axis reflects the tendency of the items to vary in the same direction and is compatible with the fact that the MMSE items are all indicators of the same concept: cognitive performance. The second and third axes identify clusters of highly correlated variables and provide support for the internal validity of the MMSE score for a French population. The full MMSE score seems to be a valid instrument for the evaluation of cognitive performance in community-based elderly residents.

Aged↗

PubMed1992

Instrumental activities of daily living as a screening tool for cognitive impairment and dementia in elderly community dwellers.

OBJECTIVE: To identify which Instrumental Activities of Daily Living (IADL) are related to cognitive impairment, independent of age, sex, and education; to assess the performance of an IADL score using these items in screening for cognitive impairment and dementia in elderly community dwellers. DESIGN: Survey based on the baseline interview of the PAQUID study on functional and cerebral aging. SETTING: Community survey in 37 randomly selected parishes in Gironde, France. SUBJECTS: Random sample of 2,792 community dwellers aged 65 and over (participation rate: 69%). MEASUREMENTS: Two-phase screening: (1) functional assessment, Mini-Mental State Examination (MMSE) and DSM-III criteria for dementia; (2) in DSM-III-positive patients, NINCDS-ADRDA criteria applied by a neurologist. Functional assessment: IADL scale of Lawton and Brody. Criterion standards: cognitive impairment: MMSE score lower than 24; dementia: DSM-III and NINCDS-ADRDA criteria. RESULTS: Four IADL items are correlated with cognitive impairment independent of age, sex, and education: telephone use, use of means of transportation, responsibility for medication intake, and handling finances. A score adding the number of IADL dependencies has a sensitivity of 0.62 and a specificity of 0.80 at the lowest cut-off point (score > 0) for the diagnosis of cognitive impairment. The same score at the same cut-off has a sensitivity of 0.94 and a specificity of 0.71 for the diagnosis of dementia. The prevalence of dementia (2.4%) is reduced by a factor of 12 in subjects independent for the four IADL. CONCLUSION: The four IADL score could be incorporated into the screening procedure for dementia in elderly community dwellers.

Activities of Daily Living↗

PubMed1992

A longitudinal assessment of seizure outcome and overall benefit from 100 cortectomies for epilepsy.

Results of 100 cortical resections for 76 temporal, 23 frontal and one parietal lobe epilepsies were studied in terms of seizure relief and overall benefit. A non-homogenous Markov chain model was used to take into account both the intravariability of post-surgical outcome and the differences in duration of follow-up in a group of patients consecutively operated. The seizure free (SF) state was defined as no seizure in the previous five months at first follow up visit and none in the preceding 12 months at subsequent annual visits. For the whole of the population the SF probability was 82%, 66%, 61%, and 62% at six months, one year, two and five years respectively. A better outcome was found for temporal lobe epilepsy (SF probability: 68% at the fifth postoperative year) than for frontal lobe epilepsy (SF probability: 42% at the fifth postoperative year) with a statistically significant difference. Pre- and postoperative interictal signs and symptoms were classified according to their clinical significance: (a) mild handicap--symptoms recognisable but no interference with usual life, and (b) moderate or severe handicap--interference with some or all daily activities. The interictal state was considered more impaired after surgery than before in two situations: (a) either symptoms, absent before surgery, appeared in the postoperative period involving a moderate or severe handicap, or (b) symptoms present before surgery and answerable for a mild or moderate handicap that increased to involve a moderate or severe handicap respectively in the postoperative period. Surgery was considered a major benefit when two conditions were fulfilled-namely, a SF state and no deterioration of the interictal stage when compared with the preoperative period. The probability of obtaining such a benefit was 58%, 51%, 48% and 56% at six months, one year, two and five years respectively. The results suggest that surgery is an effective treatment for more than 50% of long lasting medically intractable epilepsies.

Adolescent↗

PubMed1992

The Paquid epidemiological program on brain ageing.

Paquid is an epidemiological study designed to gather and follow-up a cohort of 3,777 elderly subjects (65 years and older) living at home. In order to study normal and pathological brain ageing, these subjects were randomly chosen in the general population of 75 communities of Gironde and Dordogne, two administrative areas of South-Western France. The subjects were interviewed at home by trained psychologists and followed-up with the same procedure at 1, 3 and 5 years after the initial data collection. The identification of the demented cases is made with a two-stage design: the first stage is a systematic screening by the psychologists with application of the DSM-IIIR criteria and the second stage consists in a confirmation of the diagnosis by a neurologist according to the NINCDS-ADRDA criteria. Paquid is complemented by the study of a random sample of 357 subjects living in institutions in Gironde.

Activities of Daily Living↗

PubMed1992

Elimination of atrioventricular nodal reentrant tachycardia using discrete slow potentials to guide application of radiofrequency energy.

BACKGROUND: Ablation of the slow pathway has been performed to eliminate atrioventricular (AV) nodal reentrant tachycardia (AVNRT) either by a surgical approach or by using radiofrequency catheter technique guided by retrograde slow pathway activation mapping. From previous experience of midseptal and posteroseptal mapping, we were aware of the existence of peculiar slow potentials in most humans. Postulating their role in AVNRT, we studied these potentials and the effects of radiofrequency energy. METHODS AND RESULTS: Sixty-four patients (mean age, 48 +/- 19 years) with the usual form of AVNRT were studied. Slow, low-amplitude potentials were recorded when using the anterograde AV conducting system. Slow potentials occupied all (giving a continuum of electrograms) or some of the time between the atrial and ventricular electrograms. Their most specific patterns were their progressive response to increasing atrial rates, which resulted in a dramatic decline in amplitude and slope, a corresponding increase in duration, and a separation from preceding atrial potentials until the disappearance of any consistent activity. Slow potentials were recorded along a vertical band at the mid or posterior part of the septum near the tricuspid annulus. Radiofrequency energy applied at the slow potential site resulted in interruption of induced tachycardia within a few seconds and rendered tachycardia noninducible in all patients. A median of two impulses was delivered to each patient. In 69% of patients, postablation atrial stimulation cannot achieve a long atrial-His interval, which previously was critical for tachycardia induction or maintenance. No patient had AVNRT over a follow-up period of 1-16 months, and all had preserved AV conduction. In all except two patients, the PR interval was unchanged. In 47 patients, long-term electrophysiological studies confirmed the efficacy of ablation and the nonreversibility of results by isoproterenol; however, echo beats remained inducible in 40% of patients. CONCLUSIONS: An area showing slow potentials is present at the perinodal region in humans. In patients with AVNRT, application of radiofrequency energy renders tachycardia noninducible through the preferential modification of the anterograde slow pathway. With present clinical methods, the exact origin and significance of these physiological potentials cannot be specified.

Cardiac Pacing, Artificial↗

PubMed1992

Occupation during life and memory performance in nondemented French elderly community residents.

Using data obtained during the baseline screening of the PAQUID cohort, an epidemiologic study on brain aging conducted in the Bordeaux area of France, we studied the relationship between lifetime occupation and memory performance in visual recognition (Benton Visual Retention Test; BVRT) and verbal induced recall (Wechsler Paired Associates Test; WPAT) in 2,720 elderly community residents. Occupational category was strongly correlated with poor memory performance for both the BVRT and the WPAT. Independent of the educational level, the risk of having poor memory performance was two to three times greater for farmers, domestic service employees, and blue-collar workers than for professionals/managerials. Occupational category should be taken into account in future cross-national studies on brain aging.

Aged↗

PubMed1992

[Bone risk of hormone-suppressing therapy in differentiated thyroid epithelioma. Study by dual photon absorptiometry].

A decreased bone mineral density is a well known complication of thyrotoxicosis. If bone is also adversely affected by a subclinical hyperthyroidism is still debated. Such a situation is deliberately induced for treatment of thyroid differentiated carcinoma. We compared bone mineral measurements in case of thyroid carcinoma exposed to prolonged suppressive hormonal treatment (288 patient year, LT3 in 87%) and in age and weight matched controls. We did not find any difference in both sexes between the two populations in term of fracture rate and vertebral mineral density measured by dual photon absorptiometry, nor any influence of gonadal status in women.

Absorptiometry, Photon↗

PubMed1991

Comparative efficiency of a survival-based case-control design and a random selection cohort design.

Ambidirectional studies are useful when information about disease status is available on a cohort but a risk factor has still to be recorded. An example is the study of the influence of HLA phenotypes on the progression of HIV carriers towards AIDS. An ambidirectional design is proposed in which the cases and controls are defined by the survival duration of the subjects; it includes as special cases some other ambidirectional designs. Its efficiency is compared with that of a random selection cohort design both analytically and by computer simulation. It is shown that when the size of the cohort is large, appreciable gains in power can be achieved by this type of design even when there is no censoring.

Acquired Immunodeficiency Syndrome↗

PubMed1991

[The Paquid research program on the epidemiology of dementia. Methods and initial results].

Paquid is an epidemiological study designed to gather and follow up a cohort of 4,000 elderly subjects (65 years and older) living at home in order to study normal and pathological brain aging. These subjects were randomly chosen in the general population of 75 communities of South-Western France. We present the results of the data collected from 2,792 subjects on the prevalence and the correlates of clinically diagnosed dementia. The DSM III criteria for dementia were met by 101 subjects (3.62 p. 100). These cases were reviewed by a neurologist to confirm the diagnosis and to determine the cause of dementia using the NINCDS-ADRDA criteria. Forty-three subjects were classified as probable Alzheimer's disease; 8 as possible Alzheimer's disease; 5 as vascular dementia; 5 as Parkinson's disease with dementia; 2 as alcoholic dementia; 2 as "dementified psychosis"; and 1 unclassified. Fifteen patients refused to be examined by the neurologist, 18 were false-positives, and 2 died before the neurologists visit. Using the NINCDS-ADRDA criteria, the prevalence of dementia was as low as 1.6 p. 100. The prevalence of probable Alzheimer's disease decreased dramatically as educational level increased, lung 5.4 p. 100 for subjects with no education, 1.7 p. 100 for subjects with grade school level, 0.4 p. 100 for subjects with high school level and 0.4 p. 100 for subjects with university degrees. The relationship between dementia and educational level is still controversial in the literature. In this study the sample was large and randomly selected; all the demented cases fulfilled the NINCDS-ADRDA criteria. This suggests that educational level is indeed an important correlate of dementia in the French elderly community.

Aged↗