PubMed Health⌕ Search

Biomedical subjects

L Potvin

Publications and source records attributed to L Potvin.

At least 37 records · Page 2Linked to original sources
PubMed1998

Are drivers with CVD more at risk for motor vehicle crashes? Study of men aged 45 to 70.

OBJECTIVE: To examine whether male drivers aged 45 to 70 years suffering from cardiovascular disease (CVD) are more likely to be involved in motor vehicle crashes (MVC) that are reported to the police. DESIGN: Population-based case-control study. SETTING: Data on drivers' ages and medical conditions were compiled from the Societé de l'assurance automobile du Québec's (SAAQ) computerized files. A questionnaire was mailed to all subjects to collect additional information on annual distances driven and various driving behaviours. PARTICIPANTS: Age-stratified population-based random sample. Subjects were 2504 drivers involved in MVCs during a 6-month period; controls were 2520 drivers not involved in crashes. MAIN OUTCOME MEASURES: Proportion of drivers with CVD involved in MVCs. RESULTS: Response rate to the questionnaire was 35.5%. Analysis of the SAAQ files' entire sample of 5024 drivers showed that drivers suffering from CVD were less likely to be involved in MVCs (odds ratio [OR] 0.82, 95% confidence interval [CI] 0.67 to 0.99) than drivers without CVD. Although the estimate of risk remains unchanged when adjusted for age, it becomes statistically insignificant. It also remains unchanged and statistically insignificant when adjusted for yearly distance driven and driver behaviour, as shown by responses to the questionnaire. Drivers suffering from CVD drove significantly less each year (8900 km) than drivers without medical conditions (13,000 km). CONCLUSION: This study shows no increased risk of motor vehicle crashes for drivers suffering from CVD.

Accidents, Traffic↗
PubMed1998

Psychological distress and use of ambulatory medical services in the Quebec Medicare system.

OBJECTIVE: To document the impact of psychological distress symptoms on the use of ambulatory medical services in a universal insurance coverage context. DATA SOURCES: Data from the Quebec Health Survey (1987) linked with billing data from the Quebec Medicare system. The time frame for the utilization variables is one year before and one year after the QHS survey. STUDY DESIGN: LISREL was used to test a model introducing perceived health need as an explanatory factor of the relationship between psychological distress and the number of visits to a physician. Two samples were formed from the matched file. Sample A (n = 2,000) was used in an exploratory phase to adequately specify the model. Sample B (n = 2,000) was used to confirm the results obtained with Sample A. PRINCIPAL FINDINGS: The proposed model explained 35 percent of the number of visits to a physician in Sample A and 24 percent in Sample B. The effect of psychological distress symptoms on the respondent's perceived health need was as important as the effect of physical health status. The effect of the respondent's previous health services utilization on the number of visits to a physician was also significant. CONCLUSIONS: These results may be interpreted to indicate that in a universal insurance coverage context, psychological distress is a significant predictor of perceived health need.

Adolescent↗
PubMed1997

Risk stratification after myocardial infarction using signal-averaged electrocardiographic criteria adjusted for sex, age, and myocardial infarction location.

BACKGROUND: The objectives were to investigate the factors influencing signal-averaged ECGs (SAECGs) recorded in patients after myocardial infarction (MI) and to develop criteria for predicting arrhythmic events (AEs) that account for these factors. METHODS AND RESULTS: SAECGs were recorded 5 to 15 days after MI in 2461 patients without bundle-branch block. The duration (QRSd), terminal potential (VRMS), and terminal duration (LAS) of the filtered QRS were measured. During follow-up (17 +/- 8 months), AEs (arrhythmic death; ventricular tachycardia, VT; ventricular fibrillation, VF) occurred in 80 patients (3.3%). Receiver operating characteristic curves showed that QRSd discriminated patients with all types of AEs, but VRMS and LAS discriminated only VT patients; QRSd minus LAS also discriminated AE patients. Sex, age, and MI location significantly affected the SAECG; survivors without VT or VF were divided into subgroups (2 sex x 4 age x 2 MI), and QRSd values exceeding the 70th percentile in each subgroup predicted AEs with a sensitivity of 65.4%. An unadjusted QRSd criterion showed the same overall sensitivity and specificity but with less uniform values for each subgroup. A Cox model was constructed by use of multiple prognostic indicators, and in rank order, QRSd, previous MI, and Killip class were predictive of AEs. CONCLUSIONS: SAECG adjustments for sex, age, and MI location did not improve sensitivity and specificity but produced a more uniform predictive performance. The proposed criteria are based only on QRSd, because late potentials (VRMS and LAS) did not discriminate patients with sudden death. Duration of high-level activity during QRS (QRSd-LAS) can predict AEs, suggesting that the arrhythmogenic substate involves a large mass of myocardium.

Age Factors↗
PubMed1997

Prevalence of stages of change for physical activity in rural, suburban and inner-city communities.

This study documented the differing prevalence rates for stages of change for physical activity across rural, suburban and inner city communities using survey methods and controlling for education, gender and disease status. Respondents (n = 4768) were participants in the baseline survey for the evaluation of the Québec Heart Health Demonstration Project, a health promotion program implemented in various communities throughout the province of Québec. A total of 2639 female and 2087 male parents answered a questionnaire they received from their grade 4 to grade 6 children. The questionnaire dealt with demographic information, health-related behaviors, and intentions for these behaviors. The response rates were 90%, 77% and 70% in the rural, suburban and inner city communities respectively. Results showed that prevalence rates differed significantly between communities with rural communities having the highest rates of readiness for physical activity in comparison to suburban and inner city communities. These findings suggest that above and beyond individual difference variables, structural components such as type of community are related to people's readiness for physical activity involvement.

Adult↗
PubMed1997

Regular exercise in 30- to 60-year-old men: combining the stages-of-change model and the theory of planned behavior to identify determinants for targeting heart health interventions.

The theory of planned behavior and the stages-of-change model were used to gain a clearer understanding of the factors associated with regular exercise in order to plan more effective programs in heart disease prevention. The study was conducted using a self-administered postal questionnaire sent to a sample of 2,269 men 30 to 60 years of age. Nearly a quarter (23.3%) of respondents were physically inactive, of whom 10.5% were in the precontemplation and 12.8% in the contemplation stages; 42.1% exercised less than twice a week, of whom 22.4% were in the preparation I and 19.7% in the preparation II stages. Only 34.6% were in the action stage, exercising regularly for at least 20 minutes twice a week or more with the intention of continuing to do so. Logistic regression indicated that the variables derived from the theory of planned behavior, namely attitude, subjective norm and perceived behavioral control, were differently associated with the stages of behavior. Perceived behavioral control was strongly significant in all stages. Attitude was related with stages in which individuals have intention of exercising (contemplation and preparation II). In contrast, subjective norm seemed to be associated with stages in which individuals have no intention of doing so (precontemplation and preparation I). By identifying the specific needs of sub-groups, the results can help define programs most likely to accelerate men to the stage of regular exercise, part of an effective strategy for heart health promotion in this high-risk population.

Adult↗
PubMed1997

Single-site mutations in the conserved alternating-arginine region affect ionic channels formed by CryIAa, a Bacillus thuringiensis toxin.

The role of the third domain of CryIAa, a Bacillus thuringiensis insecticidal toxin, in toxin-induced membrane permeabilization in a receptor-free environment was investigated. Planar lipid bilayer experiments were conducted with the parental toxin and five proteins obtained by site-directed mutagenesis in block 4, an arginine-rich, highly conserved region of the protein. Four mutants were constructed by replacing the first arginine in position 21 by a lysine (R521K), a glutamine (R521Q), a histidine (R521H), or a glutamic acid (R521E). A fifth mutant was obtained by replacing the fourth arginine by a lysine (R527K). Like CryIAa, the mutants formed cation-selective channels. A limited but significant reduction in channel conductance was observed for all mutants except R521H. The effect was more dramatic for the voltage dependence of the channels formed by R521K and R521Q, which was reversed compared to that of the parental toxin. This study provides the first direct evidence of a functional role for domain III in membrane permeabilization. Our results suggest that residues of the positive arginine face of block 4 interact with domain I, the putative pore-forming region of CryIAa.

Amino Acid Sequence↗
PubMed1997

Interaction between Calcium Ions and Bacillus thuringiensis Toxin Activity against Sf9 Cells (Spodoptera frugiperda, Lepidoptera).

The effects of calcium ions and modulators of calcium movement on Bacillus thuringiensis insecticidal protein toxicity were investigated with Sf9 cells (Spodoptera frugiperda, fall armyworm) by a new B. thuringiensis toxicity assay based on measurement of fluorescence of ethidium homodimer, a high-affinity DNA stain. CryIC toxicity was substantially stimulated by extracellular calcium in a dose-dependent way (in the millimolar range), while toxicity enhancement could not be replicated when calcium was replaced by barium. This incremental toxicity was reduced by cobalt and lanthanum ions, two inorganic-calcium transport inhibitors. Methoxyverapamil, a voltage-dependent calcium channel blocker, and nifedipine, an inhibitor of dihydropyridine-sensitive L-type calcium channels, had no effect on CryIC toxin activity, but BAY K 8644, an L-type calcium channel activator, increased CryIC activity at high concentrations of extracellular calcium. While A23187, a calcium ionophore, and TMB-8, an inhibitor of intracellular-calcium mobilization, did not change CryIC-induced mortality, thapsigargin, an inhibitor of calcium uptake in intracellular stores, and more particularly trifluoperazine, which inhibits calcium-calmodulin-dependent processes, increased CryIC-mediated toxicity. The incremental effect of extracellular calcium on CryIC-induced toxicity was consistent with an increased concentration of intracellular calcium.

Journal Article↗
PubMed1996

Diet and exercise profiles of 30- to 60-year-old male smokers: implications for community heart health programs.

The aim of this study was to estimate the prevalence of diet and exercise behaviors in middle-aged male smokers and identify their determinants of behaviors, with the ultimate goal of designing more effective interventions in a community heart health program. Self-administered, postal questionnaires produced a sample of n = 671 male smokers, 30 to 60 years of age residing in Laval, Quebec's second most populous city. Variables for the study were derived from the theory of planned behavior. Correspondence analysis explained 65% of the variance, classifying smokers into five groups based on diet and exercise behavior. Group 1, smokers with diet and exercise behaviors deemed inadequate for heart health, comprised 43% of the total. Groups 2 and 3, smokers with a diet deemed inadequate or needing improvement respectively, and Group 4, smokers with inadequate exercise, comprised 42% of the total. Group 5, smokers with neither of the other high-risk behaviors, comprised 15% of the total. Four significant variables contrasted Groups 1 to 4 with group 5: age, number of cigarettes smoked daily, and perceived behavioral control (PBC) in both diet and exercise. However, coefficients for age and smoking were weak for all groups. Coefficients for PBC in diet were high and negative only for smokers with an inadequate one. For PBC in exercise, they were high and negative only for smokers who exercised inadequately. Intervention groups based on specific deficiencies in diet and exercise behaviors were then identified. Therefore, the results suggest that smoking cessation programs may be made more effective by targeting specific sub-groups and by providing resources and opportunities to counteract the lack of perceived behavioral control in middle-aged male smokers vis-a-vis diet and exercise.

Adult↗
PubMed1996

Myocardial infarction patients in the 1990s--their risk factors, stratification and survival in Canada: the Canadian Assessment of Myocardial Infarction (CAMI) Study.

OBJECTIVES: This study sought to evaluate the in-hospital and postdischarge mortality of patients with an acute myocardial infarction in the 1990s. BACKGROUND: The widespread implementation of therapeutic interventions that modify the natural history of coronary artery disease has led to changes in the profile and survival of patients with an acute myocardial infarction. Although data exist for selected subsets of patients with an acute myocardial infarction, at this time there is little recent prospective information on all patients presenting with an acute myocardial infarction, particularly for survival after hospital discharge. METHODS: All patients < or = 75 years old presenting with an acute myocardial infarction between July 1, 1990 and June 30, 1992 at nine Canadian hospitals were prospectively evaluated and followed up for 1 year. From November 1991, patients of all ages were included. In two centers, recruitment continued until December 31, 1992. A total of 3,178 patients were recruited. RESULTS: The in-hospital mortality rate of patients < or = 75 years old was 8.4%, and that at 1 year after hospital discharge was 5.3%. For patients of all ages recruited after November 1, 1991, the in-hospital mortality rate was 9.9% and 7.1% for 1 year after hospital discharge. For patients < or = 75 years old, age carried an independent in-hospital but no post discharge risk. Female patients had a twofold greater risk of dying in hospital. After hospital discharge, only 1.7% of patients < or = 75 years old and 1.9% of patients of all ages died of a presumed arrhythmic death. Premature ventricular contractions had no independent prognostic value. The relatively low in-hospital (5.3%) and postdischarge (6.1%) reinfarction rate may have contributed to improved survival. A greater reinfarction rate in patients >75 years old (17.4% vs. 9.6%, p < 0.001) may have contributed to their poorer outcome. CONCLUSIONS: One-year mortality after acute myocardial infarction continues to decrease, and changes in the prognostic value of traditional methods of risk stratification have occurred.

Age Factors↗
PubMed1995

Pap recency: modeling women's characteristics and their patterns of medical care use.

BACKGROUND: Medical care use was identified as an important predictor of Pap smear use in previous studies. This study scrutinized several dimensions of women's patterns of medical care use in relation to Pap smear use. METHODS: Cross-sectional national household survey data were linked to the respondents' Quebec Medicare records for a 3-year period. Factors associated with the recency of the reported last Pap were analyzed in a subsample of women ages 18-35 years (n = 1,799) by logistic ordinal regression. The resulting models were tested in a confirmatory sample (n = 1,799). RESULTS: Three dimensions of medical care use were examined while adjusting for women's characteristics. Recency of testing was associated with the volume of ambulatory visits to general practitioners and to obstetrician-gynecologists, with the regularity of care, and with the number of different physicians visited. CONCLUSIONS: Women's pattern of medical care use, especially the regularity of care, was an important predictor of Pap recency. Results suggest targets for improvement of screening coverage and highlight the critical role of general practitioners.

Adolescent↗
PubMed1995

Chronic stressors, social support, and depression during pregnancy.

OBJECTIVES: To analyze the relationships between stressful life conditions, social support, and depressive symptomatology during pregnancy in women of low socioeconomic status and a comparison group of women of higher socioeconomic status. METHODS: Study participants were recruited from four hospital prenatal care clinics. Low socioeconomic status was defined as no more than 11 years of education and a household income below the poverty level. Higher socioeconomic status was defined as at least 12 years of education and a household income at least one and one-half times the poverty level. All subjects were nulliparous, over 18 years of age, and French-speaking. Questionnaires were administered verbally at the participants' homes during the 30th week of pregnancy, approximately. The Beck Depression Inventory was used to measure depressive symptomatology during the preceding 7 days. RESULTS: Approximately 47% of the low socioeconomic status women and 20% of the higher socioeconomic status women scored 10 or more on the Beck Depression Inventory, indicating a depressive state. Multiple regression analysis demonstrated that chronic stressors (eg, financial and housing problems), negative life events, and inadequate social support were all linked to high depressive symptomatology during pregnancy. CONCLUSION: During pregnancy, depressive symptoms are common, especially in women of low socioeconomic status, and are strongly related to socioenvironmental factors.

Adolescent↗
PubMed1995

Patterns of health services utilization and mammography use among women aged 50 to 59 years in the Québec Medicare system.

Many studies have identified physicians' recommendation as the single most important predictor of mammography use. Health services utilization is a complex phenomenon, and the contribution of the different dimensions of health services utilization on mammography use is underresearched. This study examines the specific contribution of health services utilization variables in a multivariate model of the recency of mammography use for women aged 50 to 59 years. Subjects were respondents of the 1987 Québec Health Survey. Survey data were then linked on an individual basis to the respondent's records of Medicare physicians' claims for health care services for the 3 years before the survey. This unique data set enabled the inclusion of sociodemographic variables, risk factors, health status, healthy lifestyles, and women's patterns of utilization of general and gynecologic health care services. Multivariate predictors of the recency of mammography are: having an education higher than high school, working outside home, not living in a remote area, suffering from benign breast disease, and not perceiving one's own health as good. The volume of general and gynecologic medical care is associated with the recency of mammography in independent logistic models that include women's predisposing, enabling, and need factors. This study shows that even in a universal third-party payer health care system, physicians are missing opportunities to promote breast cancer screening.

Female↗
PubMed1995

The structure of psychological distress.

In this study we describe the factor structure of the Psychological Distress Index used in the Quebec Health Survey and compare a model that includes psychophysiologic symptoms (29 items) with a model restricted to cognitive and affective symptoms only (18 items). Three samples (n = 2,000) were used to test the likelihood of these two models. Confirmatory factor analyses were carried out using LISREL VII. Logistic regression was then used to examine the association of the two versions with demographic variables and health indicators. Analysis indicates that both versions show satisfactory construct validity. Except for age, the associations observed between both versions and respondents' demographic characteristics are similar; however, the 29-item version is more strongly associated with health status indexes, suggesting a possible bias attributable to somatic items.

Adolescent↗
PubMed1994

Spectrometers for fast neutrons from solar flares.

Neutrons with energies exceeding 1 GeV are emitted in the course of solar flares. Suitable dedicated neutron spectrometers with directional characteristics are necessary for a systematic spectroscopy of solar neutrons. We report here a study of instruments based on the detection of proton recoils from hydrogenous media, with double scattering in order to provide directional information, and also a novel scheme based on the detection of radiation from the neutron magnetic dipole moment, permitting also directional detection of neutrons. Specific designs and detection systems are discussed.

Astronomy↗
PubMed1994

Utilization of a specialized clinic following an ecological accident.

On August 23, 1988, a fire broke out in a warehouse storing PCBs, forcing the evacuation of 5,500 citizens. Three days later, a specialized clinic was opened to examine and reassure the population. Seventy percent of the evacuated people showed up at the clinic. The aim of this case-control study was to identify the determinants of utilization of this clinic among the evacuated population. Cases and controls were sampled from the cohort of the evacuated adults. Both cases and controls were randomly selected among those who consulted and those who did not consult at the clinic. A logistic regression identified nine predictors of utilization: age, family type of household, annual income less than $40,000, objective and perceived exposure to the toxic smoke, reaction to the risk, perceived scale of the evacuation, number of moves during the evacuation period and consultation elsewhere with a physician. Results showed that the fear resulting from exposure created a stronger motive to consult the clinic than physical symptoms and needs.

Accidents, Occupational↗