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Biomedical subjects

J Lellouch

Publications and source records attributed to J Lellouch.

At least 19 recordsLinked to original sources
PubMed1992

Vitamin B12 among parturients and their newborns and its relationship with birthweight.

Vitamin B12 (Cobalamin) is an essential nutrient in the diet of humans, particularly during pregnancy, nevertheless very few epidemiological studies have been reported, particularly concerning variation factors. The purpose of this study is to assess the role of vitamin B12 on birthweight after taking into account potential confounders, such as obstetrical, socioeconomic, and biological factors which will be identified. This study was conducted on 188 single births occurring during a 5-month period in an obstetrical care unit in Paris. Vitamin B12 plasma levels and folate plasma levels of mothers and cords along with haematological parameters were measured. Social and obstetrical features of the mothers as well as their tobacco exposure and alcohol consumption were recorded. Cord blood vitamin B12 levels were highly correlated with maternal levels (r = 0.63, P less than 0.001) and were 2-3-fold higher. Three variation factors of vitamin B12 were identified: maternal age, ethnicity and tobacco exposure. Negative correlations between birthweight and vitamin B12 levels were observed only among the smoker group (r mothers = -0.46, P less than 0.05 and r cords = -0.42, P less than 0.05). After adjustment for ethnicity and parity, birthweight remained negatively linked to vitamin B12 in smokers. This relationship could suggest that the availability of vitamin B12 for fetal development depends on certain biological factors present only in mothers who smoked. We hypothesized this relationship could be explained, in part, by lipid metabolism, particular to smokers.

Adult↗
PubMed1992

Power and weakness of spontaneous reporting: a probabilistic approach.

It has been clearly demonstrated that spontaneous reporting remains one of the best ways for picking up new adverse drug reactions (ADRs) once a drug is on the market. The probability of revealing a new ADR by spontaneous reporting was studied as a function of reporting rate, strength of drug-event association (relative risk), background incidence of the event and number of patients treated. The model included determination of (i) the probability of reporting at least one drug-event association case and (ii) the overall probability of concluding that the drug-event association is not coincidental. Both probabilities were generally low. The results suggest that the identification of a new risk by spontaneous reporting implies a strong association between the drug treatment and the occurrence of the event.

Adverse Drug Reaction Reporting Systems↗
PubMed1992

Self-reported psychotropic drug use and associated factors in a French community sample.

Drug use was examined in a French general population adult sample from a household survey conducted in 1987-8 in a newly built town near Paris. Psychotropic drug use was measured by the percentage of subjects reporting their use during the past week. It was prominently represented by benzodiazepines (90% of psychotropic users), differed strongly between genders (4.6% in men, 10.2% in women) and age groups (higher after 40 years). A lifetime history of major depressive episode (MDE) or of anxiety disorders was associated with a higher proportion of psychotropic drug use. Psychotropic drug use also went with a current well-being questionnaire score. Using a logistic analysis, the following set of variables held for women: well-being score, history of both MDE and anxiety disorder, age, and marital status. Making allowance for the cross-sectional nature of this retrospective survey, these finding confirmed the relatively high level of benzodiazepine drug use in an urban French community sample and emphasized its association with mental health status.

Adult↗
PubMed1992

Correlated nondifferential misclassifications of disease and exposure: application to a cross-sectional study of the relation between handedness and immune disorders.

In cross-sectional studies, misclassifications of exposure and of health status may be related. For instance some subjects may tend to overreport both exposure and disease. A misclassification is said to be nondifferential if the sensitivity and the specificity which characterize it do not depend on the true status of the subjects for the other variables. Nondifferential misclassifications of two dichotomic variables may be correlated if the probability of being misclassified for one of them depends on the presence of an error of classification for the second one. Models are presented to estimate the bias induced by correlated nondifferential misclassifications on an odds ratio whose true value is unity. For most usual situations, when the great majority of the subjects are healthy and nonexposed, the influence of overreporting is shown to be larger than that of underreporting. It appears to be relatively easy to find a spurious, but significant, relationship. Real data are analysed to show that the potential consequences of correlated nondifferential misclassifications are not purely theoretical. In a sample of 1676 subjects from the general population we observed significant relations between left-hand shift and various aspects of health status: reporting a history of eczema, experience of a serious health problem in the past, experience of a serious health problem presently, use during the last month of analgesics or of drugs for circulatory problems, or digestion, consultation with a physiotherapist or hospitalization during the last year. These results, as with many similar ones previously reported, are highly suggestive of an information bias. They are less easily explained by biological hypotheses, e.g. Geschwind's theory of cerebral lateralization, than by correlated misclassifications resulting from overreporting of both the use of the left hand and the existence of some health problems by healthy right-handers. The modelling used in this report supports this hypothesis.

Adult↗
PubMed1992

A new procedure for group sequential analysis in clinical trials.

Since Pocock (1977, Biometrika 64, 191-199), many methods have been developed for group sequential analysis of clinical trials. However, these methods remain underemployed partly because of inconsistencies of sequential testing [Berry (1987, The Statistician 36, 181-189)]. This paper considers a new approach, which, by requiring that a succession of interim analyses be significant at the alpha level, both preserves the overall significance level alpha and does not present some of the inconsistencies of the previous methods. Results are obtained for a normal or binary response and for survival data. A comparison with the usual group sequential testing is also presented.

Analysis of Variance↗
PubMed1991

Some extensions to a new approach for interim analysis in clinical trials.

There already exists many methods for group sequential analysis of clinical trials. A new approach suggests to preserve the overall type I error alpha by requiring that a succession of interim analyses be significant at the alpha level. In this paper, this procedure is extended. A rule for early acceptance of H0 is presented, with an extension for flexible number and times of analyses. A real example is given.

Clinical Trials as Topic↗
PubMed1991

Age and cohort effects in adult handedness.

A systematic increase with age of the strong right-handers/mixed right-handers ratio, in normal adults, was found in Algeria, Greece, Italy, France and Spain. This age effect on adult handedness is not easily explained by variations in the social pressure against left-hand use, differential mortality, or information bias. There was no systematic decrease in the frequency of left-handedness with age. Left-hand writing among left-handers was common in the youngest age group and rare after 40 years of age.

Adolescent↗
PubMed1991

[Interim analysis in therapeutic trials: a brief survey of current developments].

It is often interesting to introduce, in the plan of a clinical trial, the possibility to make interim analyses. However, this induces an increase of type one error and it is thus necessary to use appropriate statistical methods. Usual group sequential procedures are mentioned, just as more recent approaches like flexible methods with free number and time of analyses, or like the succession procedure.

Clinical Trials as Topic↗
PubMed1990

An epidemiological reconsideration of the Geschwind-Galaburda theory of cerebral lateralization.

To contribute to the Geschwind-Galaburda theory of cerebral lateralization, we examined the relationship of left-handedness to allergic disorders and stuttering, using epidemiological data of two French samples, one of which (N = 9591) is representative of the French male population between 17 and 24 years of age. Results showed a higher frequency of stuttering but not of allergic disorders in left-handers. Extreme right-handedness was observed to be significantly associated with a lower frequency of allergic disorders; response bias might explain such a relationship. Findings were confirmed after allowing for potential confounding factors, such as age and education. In both samples, stuttering and allergic disorders were significantly related.

Adolescent↗
PubMed1990

Influence of environmental lead on membrane ion transport in a French urban male population.

Red cell cation transports (Na(+)-K+ pump, Na(+)-K+ cotransport system, Na(+)-Li+ countertransport, and Na+ and K+ passive permeabilities) and blood and hair lead levels were measured in 129 healthy adult Caucasians not occupationally exposed to lead. In agreement with previously reported in vitro results showing a lead-induced Na(+)-K+ ATPase inhibition, Na(+)-K+ pump activity was inversely correlated with hair lead (r = -0.18, P less than 0.05); it was not significantly correlated with blood lead. Na(+)-K+ cotransport activity was inversely correlated with blood lead contents (r = -0.23, P less than 0.05) but not with hair lead. No significant correlation was found between the remaining cation transport pathways and lead levels. It is hypothesized that environmental, long-term exposure to lead may result in pump inhibition, while a recent exposition to lead may result in inhibition of the Na(+)-K+ cotransport system. Further research is required in order to determine if red cell Na(+)-K+ pump and Na(+)-K+ cotransport activities are sensitive indicators of chronic and recent exposures to lead, respectively.

Adult↗
PubMed1990

Erythrocyte cation transport systems and plasma lipids in a general male population.

The relationships between five erythrocyte cation transport systems (Na(+)-K+ pump, Na(+)-K+ cotransport, Na(+)-Li+ countertransport and Na+ and K+ passive permeabilities) and plasma lipids (total plasma cholesterol, high-density lipoprotein cholesterol and triglycerides) were investigated in 129 male adult subjects with no known history of hypertension. Na+ and K+ erythrocyte contents were also considered for their possible relationships with plasma lipids. Na(+)-K+ cotransport and passive Na+ permeability were both significantly correlated with plasma triglycerides. Conversely, no significant correlation was found between erythrocyte cation transport systems or erythrocyte cation contents and total cholesterol. These findings suggest that plasma lipids can modulate erythrocyte ion transport activity in the general population.

Adult↗
PubMed1989

Efficiency of the logistic regression and Cox proportional hazards models in longitudinal studies.

Both logistic regression and Cox proportional hazards models are used widely in longitudinal epidemiologic studies for analysing the relationship between several risk factors and a time-related dichotomous event. The two models yield similar estimates of regression coefficients in studies with short follow-up and low incidence of event occurrence. Further, with just one dichotomous covariate and identical censoring times for all subjects, the asymptotic relative efficiency of the two models is very close to 1 unless the duration of follow-up is extended. We generalize this result to several qualitative or quantitative covariates. This was motivated by the analysis of mortality data from a study where all subjects are followed up during the same fixed period without loss except by death. Logistic and Cox models were applied to these data. Similar results were obtained for the two models in shorter periods of follow-up of five years or less, but not in longer periods of ten years or more, where the survival rate was lower.

France↗
PubMed1989

Anxiety disorders in a French general psychiatric outpatient sample. Comparison between DSM-III and DSM-IIIR criteria.

In a general psychiatric outpatient sample (n = 1271) gathered through a cross-national French survey, anxiety and somatoform syndromes were assessed according to DSM-III and DMS-III-revised criteria. Lifetime and one-month prevalence rates in this population are provided and the high level of comorbidity between the anxiety syndromes is noted. The patient symptom profiles for panic syndrome, simple attacks, agoraphobia and generalized anxiety are displayed. The conspicuous consequences of the modifications brought in by the Revision-anticipatory anxiety in panic syndrome, and restricted period criteria for generalized anxiety- are discussed, with the conclusion that more field study assessment is required before further revision.

Anxiety Disorders↗
PubMed1989

Short-term effects of sulphur dioxide pollution on mortality in two French cities.

To assess the short-term effects of sulphur dioxide (SO2) atmospheric pollution on mortality a study was conducted in two large French cities, using daily measures of pollution and mortality. A statistically significant association between daily SO2 pollution and respiratory deaths up to 10 days later was shown in both cities for both male and female populations together in the age group 65 years and over. No coherent results were found between SO2 pollution and cardiovascular deaths, or between suspended particulates and either respiratory or cardiovascular deaths. Particular emphasis was put on the use of correct statistical procedures using time series analysis and on the comparison of the part played by SO2 or suspended particulates on mortality.

Age Factors↗
PubMed1988

Leukocyte count and bronchial hyperresponsiveness.

The relationship of total and differential blood leukocyte counts with bronchial methacholine response was studied in a population-based sample of 324 men. Geometric mean total leukocyte counts were significantly higher in reactors (6567 cells/mm3) than in nonreactors (5732 cells/mm3; p = 0.003). After adjusting for smoking habits, a factor contributing to both an elevation in peripheral leukocyte count and an increased level of airway responsiveness, reactor status remained significantly associated with leukocyte count. This association also persisted after controlling, with a logistic model, for atopy and common cold (marker of infection) and after excluding men with a history of asthma, chronic bronchitis, or low FEV1. Study of the differential leukocyte counts has shown that an increase was present for almost every type of leukocyte, and particularly evident for neutrophils. Whether these findings reflect an association between bronchial hyperresponsiveness and cellular inflammation needs more investigation.

Adult↗