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R Slama

Publications and source records attributed to R Slama.

At least 19 recordsLinked to original sources
PubMed2006

Geographic variations in probability of pregnancy in four cities of France.

BACKGROUND: Several studies have described geographic variations in human fecundability, but this phenomenon has almost exclusively been studied at an international level rather than within a given country. Our aim was to describe geographic variations in fecundability, the monthly probability of pregnancy, between four cities of France. METHODS: We conducted a cross-sectional study in four French maternity units from Toulouse, Rennes, Lyons and Paris, among partners of pregnant women. Women were asked about the time to pregnancy (TTP) of their current pregnancy. TTP was analysed with a discrete Cox model allowing to estimate fecundability ratios (FR). RESULTS: Time to pregnancy was defined for 894 couples. There was no strong evidence of heterogeneity in fecundability between the four compared cities (p=0.05 without adjustment and p=0.25 after adjustment for behavioural and medical factors). The highest fecundability was observed in Rennes and the lowest in Toulouse (fecundability ratio (FR)=1.28, 95% CI: 1.01-1.63). Differences in fecundability were smaller between the other cities. CONCLUSION: We highlighted a possibly slightly higher fecundability in Rennes compared to Toulouse. Possible explanations for this finding are discussed. We note that the finding is consistent with previous observations indicating a higher sperm concentration among semen donors in Rennes than in Toulouse.

Cross-Sectional Studies↗
PubMed2006

[Breakthroughs in the study of the influence of environmental factors on male reproductive health].

BACKGROUND: An important part of the research effort on male reproductive health focus on two important questions: on the one side, that of the temporal deterioration of male reproductive health and, on the other head, that of the influence of exposure to environmental chemicals during intra-uterine life on health during childhood and adulthood. The concepts on endocrine disruption and testicular dysgenesis syndrome make a link between these two questions. METHODS: This work examines knowledge cumulated over the last couple of years concerning geographical and temporal variations in male reproductive health and the testicular dysgenesis syndrome. Recent results concerning the concept of endocrine disruption and on the environmental influences on male reproduction are presented, as well as on the transgenerational effects on environmental factors on the health of male children. CONCLUSIONS: Based on clinical and epidemiological data, and with the use of in vitro animal models as well as observations in wildlife, research in this field has enabled progress in the elucidation of mechanisms of action and characterization of environmental influences on male reproductive health.

Environmental Exposure↗
PubMed2005

Controlling for continuous confounding factors: non- and semiparametric approaches.

Confounding is one of the major types of bias encountered in observational epidemiologic surveys designed to study the relation between an exposure factor and a health event. A common way to remove confounding bias during the statistical analysis phase is to adjust for the confounders in a regression model. If a confounding factor is assessed as a continuous variable, it is necessary to define how the variable is entered into the regression model. In the case of logistic regression, we illustrate through simulation that coding by a binary variable or a categorical variable with broad categories may lead to substantial residual confounding. Specific approaches can be used to define a coding method that limits residual confounding. Among these, we briefly present nonparametric approaches and describe in detail several semiparametric approaches (generalised partial linear models, spline regression and fractional polynomials). These can be used to estimate the relation between a continuous factor and the health event of interest by a smooth non pre-specified function. In semiparametric models, the effect of certain covariates is coded by a parametric function, whereas the coding of one or two continuous variables is represented by a nonparametric function. These models can be used in exploratory analyses to describe dose-effect relations between the confounder and the health event, and thus help to define a relevant coding for the confounder.

Abortion, Spontaneous↗
PubMed2004

Selection bias in semen studies due to self-selection of volunteers.

BACKGROUND: Reports of a secular decrease in semen quality remain controversial, particularly due to the possibility of selection bias. We aimed to describe the potential bias due to self-selection of volunteers in semen studies involving fecund men. METHODS: Using data from the French multicentre study REPRHOM, we compared the characteristics of the partners of pregnant women for three levels of participation: completion of a refusal questionnaire (n = 698), agreement to complete the study questionnaires only (n = 676) and agreement to complete the study questionnaires and give a semen sample (n = 331, 13% of the subjects approached). RESULTS: Poorly educated men refused more often to participate than highly educated men. Semen providers were more likely to have experienced unfavourable pregnancy outcomes (odds ratio 1.68, 95% confidence interval 1.14-2.49) compared with participants completing the questionnaires only. Time to pregnancy was similar for all participants. CONCLUSIONS: This study demonstrates the existence of selection bias in semen studies associated with fertility and socio-demographic characteristics of men. The results of semen analysis for this population sample cannot be extrapolated to the whole population from which the volunteers originate. More information is required on who participates, and participation rates should be reported in semen studies to make it possible to interpret the results correctly.

Adult↗
PubMed2004

Epidemiology of male reproductive function: a field searching for tools.

BACKGROUND: An increase in the frequency of disorders of the male human reproductive organs has been described over recent decades. Neither its causes nor its consequences on fecundity, the ability of the couples to produce a live child, are clearly known. This lack of knowledge may partly be due to methodological difficulties specific to reproductive epidemiology. METHODS: We discuss the relevance and limits of some markers of the male aspects of human reproduction, focusing on semen parameters and fecundability, a measure of the probability of pregnancy. RESULTS: Semen parameters are associated with fecundability, although they have a relatively low sensitivity to detect couples with low fecundability. The study of semen parameters proved central to describe the influence of environmental factors on the male side of reproductive function. The main limitation of semen studies is low participation rates and the possible selection biases ensuing. Fecundability can be estimated by collecting waiting time to pregnancy. Its assessment in retrospective studies often excludes the least fecund, those couples remaining childless, which entails a bias and a decrease in statistical power. The prospective approach and an approach relying on the enrollment of a cross-sectional sample of the couples currently trying to obtain a pregnancy (current duration approach) do not have these limitations. Although it has never been used, the assessment of fecundability using the current duration approach is promising both for aetiologic research and monitoring. CONCLUSION: Most of the potential markers of male reproductive function are not assessed in the general population of France, with the exception of the incidence rate of testis cancer, which is currently increasing. We present some alternatives for a monitoring system of reproductive function.

Adult↗
PubMed2003

[Use of national French health insurance register to identify the current address of a cohort].

BACKGROUND: The aim of the study was to assess the efficiency of the Registre National Inter-régimes des bénéficaires de l'Assurance-Maladie (RNIAM), which is the French register of health insurance, in order to identify the present address of subjects who have lived in the Beaumont-Hague county, France, between 1978 and 1998, when they were less than 25 years old. METHODS: A cohort of 4,118 persons was defined by consulting school and civil status registers from three villages. We drew at random 824 subjects and between October 2000 and August 2001, we asked the RNIAM to locate them. For each subject, the usual identification parameters (first name, last name, birth date and eventually birth place) were provided. In case of a doubt concerning these parameters, a second request was undertaken with a slight modification. RESULTS: Altogether, 94.5% of the included people were identified by the RNIAM. Identification was better for people born in France than for those born abroad (97% versus 52%) and 84.5% of people were linked to a health insurance regimen. The RNIAM was able to identify a correct address for 68.7% of the subjects. CONCLUSION: The RNIAM seems promising for further epidemiological investigations. Nonetheless, it still remains insufficient by itself to identify addresses. Other means (tax records) should be evaluated and associated with the register data.

Adolescent↗
PubMed2002

Population mixing and leukaemia in young people around the La Hague nuclear waste reprocessing plant.

In order to investigate for an association between population mixing and the occurrence of leukaemia in young people (less than 25 years), a geographical study was conducted, for the years 1979 to 1998, in Nord Cotentin (France). This area experienced between the years 1978 and 1992 a major influx of workers for the construction of a nuclear power station and a new nuclear waste reprocessing unit. A population mixing index was defined on the basis of the number of workers born outside the French department of 'La Manche' and living in each 'commune', the basic geographical unit under study. The analyses were done with indirect standardisation and Poisson regression model allowing or not for extra-Poisson variation. Urban 'communes' were considered as the reference population. The Incidence Rate Ratio was 2.7 in rural 'communes' belonging to the highest tertile of population mixing (95% Bayesian credible interval, 95%BCI=1.2-5.9). A positive trend was observed among rural strata with increasing population mixing index (IRR for trend=1.4, 95%BCI=1.1-1.8). The risk became stronger for Acute Lymphoblastic Leukaemia in children 1-6 years old in the highest tertile of population mixing (IRR=5.5, 95%BCI=1.4-23.3). These findings provide further support for a possible infective basis of childhood leukaemia.

Adolescent↗
PubMed2002

Time to pregnancy and semen parameters: a cross-sectional study among fertile couples from four European cities.

BACKGROUND: In fertile populations, little is known about the association between semen parameters and time to pregnancy (TTP). METHODS: Pregnant women from Copenhagen, Edinburgh, Paris and Turku who conceived without medical intervention were asked for their TTP (942 couples), and their partners provided a semen sample. The proportion of morphologically normal sperm and the multiple anomalies index (MAI, ratio of the total number of anomalies to the number of abnormal sperm) were centrally estimated. We estimated rate ratios for the occurrence of a pregnancy by a discrete survival model, adjusted for sexual activity and female factors affecting fecundity. RESULTS: Increasing sperm concentration influenced TTP up to 55 x 10(6)/ml. The proportion of morphologically normal sperm influenced TTP up to 39% according to David's criteria, and this association held among the subjects with a sperm concentration >55 x 10(6)/ml. For strict criteria, the threshold value was 19% normal sperm. An increase of 0.5 in MAI was associated with an adjusted rate ratio for the occurrence of a pregnancy of 0.68 (95% confidence interval: 0.54-0.85). CONCLUSIONS: These results highlight the importance of sperm morphology parameters and indicate that the effect of proportion of normal sperm on TTP may be independent of sperm concentration.

Cross-Sectional Studies↗
PubMed2002

[Ionizing radiation and health: data and objectives].

Three dimensions must be considered to analyze the consequences of exposure to ionozing radiation on public health: assessment of exposure, measure of the public health risk, and monitoring the perception of risk by the population. We reviewed these three dimension for several situations of exposure to ionizing radiation: exposure related to the Chernobyl accident, occupational exposure, military-related exposure and medical exposure. For each situation, we discuss the pertinence of available data an monitoring systems used in France, and propose when necessary new systems. An extension of the cancer registries to the entire country would be a significant progress in terms of research and surveillance. This must be discussed in terms of potential utility in other domains of public health.

Female↗
PubMed2001

Regional differences in waiting time to pregnancy among fertile couples from four European cities.

BACKGROUND: A previous European study found a longer time to pregnancy (TTP) among fertile women from Paris compared with women from other Western European countries. A co-ordinated, cross-sectional study of pregnant couples from Denmark (Copenhagen), France (Paris), Scotland (Edinburgh) and Finland (Turku) was therefore undertaken to assess differences in waiting TTP among couples from these cities. METHODS: Pregnant women were invited to participate when they showed up for their first antenatal visit in one of the four centres. Inclusion criteria included that their partner was 20-45 years of age and born in the country in which he was currently living and that the pregnancy was achieved without fertility treatment. Both partners filled in a questionnaire and the man underwent a physical examination and delivered a semen sample (Turku: n = 237, Copenhagen: n = 302, Edinburgh: n = 212, Paris: n = 191). RESULTS: French couples had a decreased probability of conception compared with couples from the other three countries, although only after adjustment for confounders. No significant differences between couples from the three other countries were found. CONCLUSION: The observed geographical differences in TTP remain unexplained and were not due to differences in semen quality, but may be caused by varying exposures to environmental factors or psychological distress. In addition, selection bias due to the low participation rates cannot be ruled out. Future studies examining the causes for geographical differences in TTP are needed.

Adult↗
PubMed2001

The incidence of childhood leukaemia around the La Hague nuclear waste reprocessing plant (France): a survey for the years 1978-1998.

BACKGROUND: A previous study has suggested an increased incidence rate of leukaemia from 1978 to 1992 in people aged 0 to 24 years and living in the vicinity of the La Hague nuclear waste reprocessing plant without considering age and cytological type. SETTING: The Nord Cotentin region (France) and the island of Alderney (United Kingdom). STUDY OBJECTIVE: To describe the occurrence of leukaemia for each age group and cytological type from 1978 to 1998 in the same area, using accurate reference incidence rates and adequate estimation of the at risk population. DESIGN: A geographical study of incidence using three zones defined according to their distance from the site (0 to 10 km: Beaumont-Hague electoral ward, 10 to 20 km and 20 to 35 km) has been conducted. The risk of leukaemia was estimated from the standardised incidence ratio (SIR) of the number of cases observed to the number expected. Exact 95% confidence intervals (CI) have been computed. PARTICIPANTS: All people under the age of 25 years living in the study region between 1978 and 1998. MAIN RESULTS: The observed number of cases of leukaemia in the study region as a whole was consistent with the expected value (SIR=1.03; 95%CI: 0.73, 1.41). No cases were observed on Alderney. The SIR in the Beaumont-Hague electoral ward was 2.17 (95%CI: 0.71, 5.07). The highest SIR was observed in the 5 to 9 years age group (SIR=6.38; 95%CI: 1.32, 18.65). This consists in acute lymphoblastic leukaemia cases. CONCLUSION: This study indicates an increased incidence of leukaemia in the area situated at less than 10 km from the plant. Monitoring and further investigations should be targeted at acute lymphoblastic leukaemia occurring during the childhood incidence peak (before 10 years) in children living near the La Hague site and may be other nuclear reprocessing plants.

Adolescent↗
PubMed2001

[Value of maximum expiratory volume per second and peak expiratory flow monitoring in asthma. 77 patients].

A retrospective study was conducted on a sample of 77 subjects to assess the interest of computerized flowmeter "one-flow" in the diagnosis and follow up of asthma. 77 patients and a control group matched for age and sex, measured four times by day, the forced expiratory volume in one second as well as the peak expiratory flow during 15 to 30 days. The monitoring of these two variables allowed to participate to the exclusion from the study of fifteen patients whose asthma diagnosis was informed. It also allowed the confirmation of four occupational asthma. Concerning the adherence of the treatment by patients, the conclusion of the study showed that 47% of patients modified their treatment at home without consulting their doctors, 38% resorted to their doctor and only 3% resorted to the emergencies.

Adolescent↗