Biomedical subjects

L Blais

Publications and source records attributed to L Blais.

9 recordsLinked to original sources

PubMed1997

A rapid method for the determination of vitamin E forms in tissues and diet by high-performance liquid chromatography using a normal-phase diol column.

This paper describes a simple method for the analysis of tocopherols in tissues by which frozen tissues-70 degrees C were pulverized at dry ice temperatures (-70 degrees C) and immediately extracted with hexane. There was no need to remove the coeluting lipids from tissues by saponification, since at that level of neutral lipids in the sample, there was no reduction in fluorescence response. For the analysis of oil, in which large amounts of neutral lipids were coextracted, a 20% reduction of fluorescence response was observed, but the response was equal for all tocopherol forms, and was appropriately corrected. Saponification was used only when tocopherol esters were present, and only after an initial hexane extraction to remove the free tocopherols in order to avoid their loss by saponification, particularly non alpha-tocopherol and tocotrienols. All the tocopherols and tocotrienols were separated on a normal-phase diol (epoxide) column that gave consistent and reproducible results, without the disadvantages of nonreproducibility with silica columns, or the lack of separation with reversed-phase columns. The tocopherols were quantitated by using a tocopherol form not present in the sample as an internal tocopherol standard, or using an external tocopherol standard if all forms were present, or when the sample was saponified. Piglet heart and liver samples showed the presence of mainly alpha-tocopherol, with minor amounts of beta- and gamma-tocopherol and alpha-tocotrienol, but no delta-tocopherol. Only small amounts of tocopherol esters were present in the liver but not in the heart.

Animals↗

PubMed1997

First-time use of newer oral contraceptives and the risk of venous thromboembolism.

Recent epidemiologic studies reported that the risk of venous thromboembolism (VTE) was higher with the use of the newer third generation oral contraceptives than with second generation agents. Although the overall findings of these studies are similar, the results, as they relate to patterns and duration of oral contraceptive use particularly among first-time users, are inconsistent. We reanalyzed data from the Transnational case-control study to assess the risk of VTE associated with first-time use of oral contraceptives as a function of its duration of use. Over the period 1993 to 1995, 471 cases of venous thromboembolism were identified in Germany and the United Kingdom. For each case, up to four controls were obtained, for a total of 1772 controls. Data on oral contraceptive use and confounding variables, including data on sociodemographic, lifestyle, medical history, and family history of disease, were obtained by interview. Data analysis was based on the 105 cases and 422 controls who were first-time users of second or third generation agents, or never users of oral contraception. Rate ratios, adjusted for confounders and approximated by odds ratios, were estimated as a continuous function of duration of oral contraceptive use by logistic regression and quadratic spline models. We found, for first-time users, that the adjusted rate ratio of VTE as a function of the duration of oral contraceptive use is essentially identical for second and third generation pills relative to never users. This rate ratio increases to around 10 in the first year of use and decreases to around two after 2 years of use, remaining at this risk level thereafter for both second and third generation agents. We conclude that second and third generation agents are associated with identical risks of venous thromboembolism when they are prescribed to women who are using oral contraceptives for the first time ever.

Adult↗

PubMed1996

Confounding by indication and channeling over time: the risks of beta 2-agonists.

A previously published nested case-control study, the Saskatchewan Asthma Epidemiologic Project (SAEP) spanning 1980-1987, investigated the risk of fatal or near fatal asthma and found different risks for two inhaled beta 2-agonists, fenoterol and salbutamol. The authors assessed whether this comparison was confounded by indication because of channeling of inhaled fenoterol to more severely afflicted asthmatics. Using three subcohorts selected from a cohort of 12,301 asthmatics assembled from the computerized databases of Saskatchewan Health and followed over 7 years, the authors studied two forms of channeling and investigated whether greater asthma severity and less well-controlled disease were associated with preferential prescribing of a first prescription of inhaled fenoterol, as opposed to inhaled salbutamol, and whether they were associated with the likelihood of a switch from inhaled salbutamol to fenoterol as well as a switch from inhaled fenoterol to salbutamol. The authors found that the initial choice between fenoterol and salbutamol was independent of the severity of the asthma and disease control, but that preferential prescribing of fenoterol occurred among users of salbutamol who showed signs of increased severity or uncontrolled asthma. The switch from inhaled fenoterol to salbutamol was, however, minimally related to asthma severity. They conclude that the comparison between inhaled fenoterol and salbutamol in the SAEP may have been biased by indication. This study demonstrates that long-term information on medication use is essential to ensure that the results of such case-control studies are not biased by indication.

Administration, Inhalation↗

PubMed1996

Increased morbidity and mortality related to asthma among asthmatic patients who use major tranquillisers.

OBJECTIVE: To assess the potentially increased risk of death or near death from asthma in asthmatic patients with psychosis. DESIGN: Case-control study. SETTING: The computerised health databases of the Canadian province of Saskatchewan. SUBJECTS: 131 cases of death or near death from asthma identified within a cohort of asthmatic patients; 3930 matched non-cases. EXPOSURE AND OUTCOME MEASURES: The exposure of interest was the use of major tranquillisers in the period before an outcome event. Outcomes included death or near death from asthma. RESULTS: Crude analyses showed that asthmatic patients who had used major tranquillisers in the previous 12 months were at a 3.2 (95% confidence interval 1.4 to 7.5) times greater risk of death or near death from asthma than asthmatic patients who did not use major tranquillisers. Past users of major tranquillisers who had recently discontinued use were at a particularly high risk (relative risk 6.6; 2.5 to 17.6). Adjustment for use of antiasthma drugs and other confounders abolished this excess risk. CONCLUSIONS: Asthmatic patients who use major tranquillisers seem to be at an increased risk of death or near death from asthma. Physicians treating asthmatic patients with a history of use of major tranquillisers should exercise greater caution with regard to management of such patients.

Adolescent↗

PubMed1996

Bronchodilators and acute cardiac death.

Bronchodilators used in the treatment of airway disease have been shown to have a variety of cardiac effects that may contribute to the occurrence of life-threatening events such as cardiac arrhythmias and cardiac arrest. We investigated whether theophylline and beta-agonists were associated with cardiovascular mortality among a cohort of subjects prescribed antiasthma medications. We used a population-based cohort of 12,301 subjects aged 5 to 54 yr, formed from health-insurance data bases from Saskatchewan, Canada, and spanning the period 1978 to 1987. Within this cohort, we identified all 30 deaths from cardiovascular causes in which acute asthma did not appear to be a contributing factor. We identified all asthma and cardiovascular drugs dispensed to these subjects shortly before their deaths and compared this therapy to that dispensed to a random sample of 4,080 person-time controls. After adjustment for age and the prior use of cardiac drugs, the rate of cardiovascular death was greater in users of theophylline, with a rate ratio (RR) of 2.7 (95% Cl:1.2 to 6.1), and in users of beta-agonists taken orally or by nebulizer (RR = 2.4; 95% Cl:1.0 to 5.4), but not in users of beta-agonists administered by metered-dose inhaler (RR = 1.2; 95% Cl:0.5 to 2.7). The great majority of cardiovascular deaths occurred among subjects with clinical or pathologic evidence of potentially lethal conditions. These results suggest that the use of theophylline and of beta-agonists administered orally or by nebulization should be avoided in subjects with significant cardiac disease or at high risk for such disease, especially acute coronary insufficiency and congestive cardiomyopathy. On the other hand, the use of beta-agonists administered by metered-dose inhalers (MDIs) was not associated with an increased risk of cardiovascular death.

Adolescent↗

PubMed1995

Binary regression with continuous outcomes.

Clinical research often involves continuous outcome measures, such as blood cholesterol, that are amenable to statistical techniques of analysis based on the mean, such as the t-test or multiple linear regression. Clinical interest, however, frequently focuses on the proportion of subjects who fall below or above a clinically relevant cut-off value, as a measure of the risk of disease. The customary approach to analyse such data is to dichotomize the continuous outcome measure and use statistical techniques based on binary data and the binomial distribution. In this paper, we use a parametric approach and the framework of generalized linear models to fit various regression models, including the logistic, on the basis of the original continuous outcome. We consider the Gaussian and the three-parameter log-normal distributions for the continuous outcome, assessing both precision and bias under various conditions. In simulation analyses, we find that we are unable to fit some of the samples with the 'dichotomous' approach, but we can with the 'continuous' approach, and that the latter yields estimates between 25 and 85 per cent more efficient than the former. We illustrate the method, programmed using GLIM macros, with data from clinical studies of the risk of hypoxaemia during open thoracic surgery and the risk of nocturnal hypoglycaemia among diabetic children.

Diabetes Mellitus, Type 1↗

PubMed1994

A cohort analysis of excess mortality in asthma and the use of inhaled beta-agonists.

The association between the use of inhaled beta-agonists and the risk of death and near-death from asthma has previously been reported. It was based on a nested case-control study of 129 cases and 655 control subjects selected from a cohort of 12,301 users of asthma drugs followed during the period 1980 through 1987. In this paper we examine the question of asthma and non-asthma mortality using data from the entire cohort of 12,301 asthmatics. There were 46 asthma and 134 non-asthma deaths in this cohort, for which there were 47,842 person-years of follow-up. The overall rate of asthma death was 9.6 per 10,000 asthmatics per year. This rate varied significantly according to the use of fenoterol, albuterol, or oral corticosteroids in the prior 12 months and the number of asthma hospitalizations in the prior 2 years. The rate decreased significantly, by 0.6 asthma deaths per 10,000 asthmatics per year over the study period, after controlling for the effect of the four other risk factors. It also increased significantly with the use of all beta-agonists, and more so for fenoterol than for albuterol, although this difference was partly explained by the dose inequivalence of the two drugs. Change-point dose-response curves showed that the risk of asthma death began to escalate drastically at about 1.4 canisters (of 20,000 micrograms each) per month of inhaled beta-agonist, the recommended limit. For non-asthma death, the overall rate of 28 deaths per 10,000 asthmatics per year was not related to the use of inhaled beta-agonists.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗

PubMed1994

Patterns of increasing beta-agonist use and the risk of fatal or near-fatal asthma.

The association between the use of inhaled beta-agonists by metered-dose inhaler and the risk of fatal or near-fatal asthma has been demonstrated. It shows that asthmatics who use one canister of beta-agonist per month more than the number used by other similar asthmatics have twice the risk of fatal or near-fatal asthma. The present investigation assesses the magnitude of this excess risk when an asthmatic increases his/her own monthly use of inhaled beta-agonists over time. From a previous nested case-control study of 129 deaths and near-deaths from asthma (cases) and 655 controls from a cohort of 12,301 asthmatics, the subset using at least 12 inhalers during the 12 month study period was identified (97 cases and 258 controls). A profile score, ranging 0-11, was formed to quantify the patterns of beta-agonist use over time for each subject, covering the entire spectrum extending from decreasing to increasing use. The relative risk was 15.2 (95% confidence interval (CI) 2.4-96.2) per unit increase of the profile score in subjects with a pattern of increasing beta-agonist use (profile score of 6.5 or more), but this relative risk was only 1.5 (95% CI 0.8-2.6) per unit when the profile score was less than 6.5 (non-increasing use). This relative risk was independent of the risk associated with the total quantity of beta-agonist use in the 12 month period, which remained around 1.6 (95% CI 1.3-2.0) per inhaler per month.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗

PubMed1991

[Poverty, mental health and survival strategies].

The relation between "poverty and mental health" has long been established. However, the dynamic underlying the relation between social and psychic processes has received much less attention. This article presents certain preliminary results of research whose aim is to promote the emergence of the multiple dimensions behind the problematic of mental health in social conditions characterized by extreme poverty. In addition, the authors base their approach on the assumption that human beings, even underprivileged, are very active players, and explore the strategies that are hereby developed in order to maintain or recover their equilibrium.

Adaptation, Psychological↗