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S Medina

Publications and source records attributed to S Medina.

At least 55 records · Page 3Linked to original sources
PubMed1998

[Short-term modeling of the effect of air pollution on health. Example: SO2 and total mortality, Paris 1987-1999].

Since 1990, many epidemiological time series studies have provided evidence that ambient air pollution levels have adverse health effects. The ERPURS study (Evaluation des Risques de la Pollution Urbaine pour la Santé) has permitted to quantify this impact in the Paris region. This study was based on an ecological time series approach. We present, step by step, the method used, illustrated by an example: association between SO2 levels and total mortality (excluding external causes), 1987-1990. Mortality modelling has taken trend into account by a linear term, seasons by trigonometrics functions sum, day of the week effects by 6 dummy variables, temperature peak by a dummy variable, influenza epidemics by appropriate variables, mean temperature by linear and quadratic terms, relative humidity by a linear term. SO2 1 day lag was introduced in the model by a linear term. The central issue is the control of seasonal variations and long term trend. An inadequate control can lead to some spurious results. The relationship between mortality and weather variables is generally nonlinear. The use of statistical and graphical diagnostics, are necessary at each step. Time series analysis are important tools to study short term relationship between air pollutants and health indicators. The method applied in the ERPURS study is only one of the possible approaches. Whatever the method used, it is important to understand the underlying process of the data and to control for confounding factors with the appropriate method for the temporal structure of the data.

Air Pollutants↗
PubMed1997

Short-term effects of ambient sulphur dioxide and particulate matter on mortality in 12 European cities: results from time series data from the APHEA project. Air Pollution and Health: a European Approach.

OBJECTIVES: To carry out a prospective combined quantitative analysis of the associations between all cause mortality and ambient particulate matter and sulphur dioxide. DESIGN: Analysis of time series data on daily number of deaths from all causes and concentrations of sulphur dioxide and particulate matter (measured as black smoke or particles smaller than 10 microns in diameter (PM10)) and potential confounders. SETTING: 12 European cities in the APHEA project (Air Pollution and Health: a European Approach). MAIN OUTCOME MEASURE: Relative risk of death. RESULTS: In western European cities it was found that an increase of 50 micrograms/m3 in sulphur dioxide or black smoke was associated with a 3% (95% confidence interval 2% to 4%) increase in daily mortality and the corresponding figure for PM10 was 2% (1% to 3%). In central eastern European cities the increase in mortality associated with a 50 micrograms/m3 change in sulphur dioxide was 0.8% (-0.1% to 2.4%) and in black smoke 0.6% (0.1% to 1.1%). Cumulative effects of prolonged (two to four days) exposure to air pollutants resulted in estimates comparable with the one day effects. The effects of both pollutants were stronger during the summer and were mutually independent. CONCLUSIONS: The internal consistency of the results in western European cities with wide differences in climate and environmental conditions suggest that these associations may be causal. The long term health impact of these effects is uncertain, but today's relatively low levels of sulphur dioxide and particles still have detectable short term effects on health and further reductions in air pollution are advisable.

Air Pollutants↗
PubMed1997

Air pollution and doctors' house calls: results from the ERPURS system for monitoring the effects of air pollution on public health in Greater Paris, France, 1991-1995. Evaluation des Risques de la Pollution Urbaine pour la Santé.

This study examines short-term relationships between doctors' house calls and urban air pollution in Greater Paris for the period 1991-1995. Poisson regressions using nonparametric smoothing functions controlled for time trend, seasonal patterns, pollen counts, influenza epidemics, and weather. The relationship between asthma visits and air pollution was stronger for children. A relative risk (RRP95/P5) of 1.32 [95% confidence interval (CI) = 1.17-1.47)] was observed for an increase from the 5th to the 95th percentile (7-51 micrograms/m3) in daily concentrations of black smoke (BS). The risks for 24-hr sulfur dioxide and nitrogen dioxide levels were in the same range. Cardiovascular conditions, considered globally, showed weaker associations than angina pectoris/myocardial infarction, for which RRP95/P5 was 1.63 (95% CI = 1.10-2.41) in relation to ozone ambient levels. Eye conditions were exclusively related to ozone (RRP95/P5 = 1.17, 95% CI 1.02-1.33). Asthma visits and ozone showed an interaction with minimum temperature: an effect was observed only at 10 degrees C or higher. In two-pollutant models including BS with, successively, SO2, NO2, and O3, only BS and O3 effects remained stable. Along with mortality and hospital admissions, house call activity data, available on a regular basis, may be a sensitive indicator for monitoring health effects related to air pollution.

Air Pollutants↗
PubMed1997

Air pollution and daily admissions for chronic obstructive pulmonary disease in 6 European cities: results from the APHEA project.

We investigated the short-term effects of air pollution on hospital admissions for chronic obstructive pulmonary disease (COPD) in Europe. As part of a European project (Air Pollution and Health, a European Approach (APHEA)), we analysed data from the cities of Amsterdam, Barcelona, London, Milan, Paris and Rotterdam, using a standardized approach to data eligibility and statistical analysis. Relative risks for daily COPD admissions were obtained using Poisson regression, controlling for: seasonal and other cycles; influenza epidemics; day of the week; temperature; humidity and autocorrelation. Summary effects for each pollutant were estimated as the mean of each city's regression coefficients weighted by the inverse of the variance, allowing for additional between-cities variance, as necessary. For all ages, the relative risks (95% confidence limits (95% CL)) for a 50 microg x m(-3) increase in daily mean level of pollutant (lagged 1-3 days) were (95% CL): sulphur dioxide 1.02 (0.98, 1.06); black smoke 1.04 (1.01, 1.06); total suspended particulates 1.02 (1.00, 1.05), nitrogen dioxide 1.02 (1.00, 1.05) and ozone (8 h) 1.04 (1.02, 1.07). The results confirm that air pollution is associated with daily admissions for chronic obstructive pulmonary disease in European cities with widely varying climates. The results for particles and ozone are broadly consistent with those from North America, though the coefficients for particles are substantially smaller. Overall, the evidence points to a causal relationship but the mechanisms of action, exposure response relationships and pollutant interactions remain unclear.

Air Pollution↗
PubMed1997

C-terminal parathyroid hormone-related protein inhibits proliferation and differentiation of human osteoblast-like cells.

Parathyroid hormone-related protein (PTHrP) is synthesized by osteoblasts, although its local role in bone is not completely understood. The C-terminal (107-111) region of PTHrP seems to be a potent inhibitor of osteoblastic bone resorption. We studied the effect of this PTHrP domain on the proliferation and synthesis of osteoblastic markers in osteoblast-like cells from adult human bone. We found that the human (h)PTHrP(107-139) fragment, between 10 fM and 10 nM, inhibited 3H-thymidine incorporation into these cells. The antiproliferative effect of the latter fragment, or that of hPTHrP(107-111), was similar to that induced by [Tyr34] hPTHrP(1-34) amide, bovine PTH(1-34), and hPTHrP(1-141), while hPTHrP(38-64) amide was ineffective. Human PTHrP(7-34) amide, at 10 nM, and 1 microM phorbol-12-myristate-13-acetate also significantly decreased DNA synthesis in human osteoblast-like cells. Neither hPTHrP(7-34) amide nor hPTHrP(107-139), at 10 nM, stimulated protein kinase A (PKA) activity in these cells. Moreover, 100 nM H-89, a PKA inhibitor, did not eliminate the inhibitory effect of hPTHrP(107-139) on these cells' growth. However 100 nM calphostin C, a PKC inhibitor, blunted this effect of PTHrP(107-139). In addition to their antimitogenic effect, hPTHrP(107-139) and hPTHrP(107-111) inhibited basal and 1,25-dihydroxyvitamin D3 (1,25(OH)2D3)-stimulated alkaline phosphatase activity in these cells. Both fragments, like 1,25(OH)2D3, decreased C-terminal type I procollagen secretion into the cell-conditioned medium, but osteocalcin secretion by these cells was unaffected by the C-terminal PTHrP fragments. These findings suggest that PTHrP may act as a local regulator of bone formation.

Aged↗
PubMed1996

[Vitamin D levels in patients with hip fracture in Madrid].

BACKGROUND: Vitamin D appears to be implicated in the loss of bone mass and its most severe complication is the hip fracture. A change is produced in the metabolism of vitamin D in elderly people although its study has received little attention in many countries. METHODS: With the aim of evaluating vitamin D and its metabolites in the elderly people with hip fracture in our geographic environment (Madrid, Spain), 58 patients with hip fracture over the age of 70, and 39 subjects without a fracture or the similar age were studied. Both groups were evaluated during the season of minimum solar irradiation. The plasma concentrations of intact PTH and the serum concentrations of calcidiol and calcitriol were studied in all the patients. RESULTS: The patients with hip fracture presented significantly lower concentrations of calcidiol (11.7 +/- 6.4 vs. 18.4 +/- 12.7 nmol/l) and calcitriol (60.1 +/- 24.7 vs. 76.1 +/- 25.0 pmol/l) than in elderly persons without fracture, with similar PTH values being observed in both groups (4.8 +/- 1.9 vs. 5.1 +/- 2.3 pmol/l). CONCLUSIONS: Although Madrid, Spain is considered to be a geographical area of high solar irradiation, the elderly population studied presented a vitamin D deficiency which was found to be greater in those with hip fracture.

Age Factors↗
PubMed1996

Short term effects of air pollution on health: a European approach using epidemiologic time series data: the APHEA protocol.

BACKGROUND AND OBJECTIVES: Results from several studies over the past five years have shown that the current levels of pollutants in Europe and North America have adverse short term effects on health. The APHEA project aims to quantifying these in Europe, using standardised methodology. The project protocol and analytical methodology are presented here. DESIGN: Daily time series data were gathered for several air pollutants (sulphur dioxide; particulate matter, measured as total particles or as the particle fraction with an aerodynamic diameter smaller than a certain cut off, or as black smoke; nitrogen dioxide; and ozone) and health outcomes (the total and cause specific number of deaths and emergency hospital admissions). The data included fulfilled the quality criteria set by the APHEA protocol. SETTING: Fifteen European cities from 10 different countries with a total population over 25 million. METHODOLOGY: The APHEA collaborative group decided on a specific methodological procedure to control for confounding effects and evaluate the hypothesis. At the same time there was sufficient flexibility to allow local characteristics to be taken into account. The procedure included modelling of all potential confounding factors (that is, seasonal and long term patterns, meteorological factors, day of the week, holidays, and other unusual events), choosing the "best" air pollution models, and applying diagnostic tools to check the adequacy of the models. The final analysis used autoregressive Poisson models allowing for overdispersion. Effects were reported as relative risks contrasting defined increases in the corresponding pollutant levels. Each participating group applied the analyses to their own data. CONCLUSIONS: This methodology enabled results from many different European settings to be considered collectively. It represented the best available compromise between feasibility, comparability, and local adaptibility when using aggregated time series data not originally collected for the purpose of epidemiological studies.

Air Pollutants↗
PubMed1996

Short term respiratory health effects of ambient air pollution: results of the APHEA project in Paris.

STUDY OBJECTIVE: To quantify the short term respiratory health effects of ambient air pollution in the Paris area. DESIGN: Time series analysis of daily pollution levels using Poisson regression. SETTING: Paris, 1987-92. MEASUREMENTS AND MAIN RESULTS: Air pollution was monitored by measurement of black smoke (BS) (15 monitoring stations), sulphur dioxide (SO2), nitrogen dioxide (NO2), particulate matter less than 13 microns in diameter (PM13), and ozone (O3) (4 stations). Daily mortality and general admissions to public hospitals due to respiratory causes were considered. The statistical analysis was based on a time series procedure using linear regression modelling followed by a Poisson regression. Meterological variables, epidemics of influenza A and B, and strikes of medical staff were included in the models. The mean daily concentration of PM13 and daily 1 hour maximum of SO2 significantly affected daily mortality from respiratory causes. An increase in the concentration of PM13 of 100 micrograms/m3 above its 5th centile value increased the risk of respiratory death by 17%. PM13 and BS were also associated with hospital admissions due to all respiratory diseases (4.1% increased risk when the BS level exceeded its 5th centile value by 100 micrograms/m3). SO2 levels consistently influenced hospital admissions for all respiratory diseases, chronic obstructive pulmonary disease, and asthma. Asthma was also correlated with NO2 levels. CONCLUSIONS: These results indicate that even though the relative risk is weak in areas with low levels of pollution, ambient air pollution, and especially particulate matter and SO2, nonetheless require attention because of the number of people exposed and the existence of high risk groups.

Adolescent↗
PubMed1996

Urban air pollution is still a public health problem in Paris.

By correlating data obtained from environmental indicators and health indicators over a five-year period, a system for measuring the effects of air pollution on health has been established and tested. Rises in air pollution levels do appear to be accompanied by increases in the relevant health problems.

Aged↗
PubMed1995

[Emergency admission in public hospitals in Ile-de-France].

In order to describe the population requiring an emergency admission in public hospitals in Paris Ile-de-France region, 7 358 hospitalization records were selected in a large morbidity data base. This sample is representative of emergency hospitalizations in the public hospitals of Paris-Ile-de-France region. There were slightly more women and patients were more often hospitalized in a hospital in their neighbourhood. Medical advice before going to hospital was rare. The mean length of stay was 9.5 days. The main pathologies leading to emergency hospitalizations were trauma and intoxication, pregnancy and delivery, and cardiovascular disease. The annual emergency hospitalization rate was 33 per 1 000 for Paris-Ile-de-France inhabitants of all ages. Limits and advantages of the results are discussed.

Adolescent↗
PubMed1993

[Urban atmospheric pollution and mortality: analysis of epidemiological studies published between 1980 and 1991].

This paper analyses 14 epidemiologic investigations (published from January 1980 to September 1991) about the relationship between urban air pollution and mortality. Air pollution indicators and mortality indicators are examined. Methods to analyse the relationships between these two kinds of indicators are classified according as they bring "qualitative information" trying to answer the question: "is there any relationship between air pollution and mortality?" or according as they try to quantify this relationship. Results are presented by author. Confounding factors and means to take them into account are described. This paper ends by a discussion about interest and limits of these studies. It emphasizes the importance of the collaboration between metrologists of urban air pollution and epidemiologists.

Air Pollutants↗
PubMed1992

[Leukocytoclastic vasculitis associated with tumors].

We report 6 patients with the diagnosis of leukocyclastic vasculitis, with a neoplasia as the only clinical manifestation associated. Evolution of vasculitis was chronic or recidivant; rapid erythrocyte sedimentation rate, positivity for rheumatoid factor, and hypocomplementemia were frequent in our cases. The clinical course of vasculitis and tumour was discordant. The authors believe that there are not sufficient data to demonstrate an association between leukocytoclastic vasculitis and tumours.

Adult↗