Biomedical subjects

Marie-France Valois

Publications and source records attributed to Marie-France Valois.

5 recordsLinked to original sources

PubMed2006

An S-Plus function to calculate relative risks and adjusted means for regression models using natural splines.

We provide for generalized linear regression models that use natural cubic splines to model predictors an S-Plus function to calculate relative risks (RR), log relative risk (logRR), mean percent change (MPC) for continuous covariates modeled using a logarithmic link as well as adjusted means differences (MD) for the identity link. The function makes explicit use of the natural spline basis functions, the estimated coefficients for each natural spline basis function, and the fitted correlation matrix for the estimated coefficients and can thus accommodate any number of degrees of freedom. The main function produces a publication-quality graph of all of these quantities as compared to a user-specified reference value as well as the associated confidence limits. In another function, specific values of these statistics comparing a vector of values of the independent variable to the reference value can be calculated rather than plotted.

Regression Analysis↗

PubMed2005

Associations between ambient air pollution and daily mortality among persons with diabetes and cardiovascular disease.

BACKGROUND: Recent studies suggest that persons with diabetes and with cardiovascular disease may be at higher risk for the short-term effects of air pollution. We carried out this mortality time series study in Montreal, Quebec, Canada to confirm these observations and to determine whether diabetics who had other health conditions were also at higher risk of dying when air pollution increases. METHODS AND RESULTS: In one analysis, we related daily deaths from diabetes (using the underlying cause) to daily concentrations of particles and gaseous pollutants. In another analysis, we created subgroups by identifying subjects diagnosed 1 year before death with diabetes and other major health conditions from billing and prescription data from the universal Quebec Health Insurance Plan. The analysis made use of parametric log-linear Poisson models that were adjusted for long-term temporal trends and daily weather conditions. We found positive associations between most air pollutants and daily mortality from diabetes as well as among subjects diagnosed with diabetes 1 year before death. In the latter group of subjects, greater effects were found generally in the warm season and especially among subjects who had diabetes and who also had any cardiovascular disease, chronic coronary disease, and atherosclerosis. We did not find evidence of associations among persons who only had diabetes (i.e., did not also have cancer, cardiovascular disease, or lower respiratory disease). CONCLUSIONS: These data indicate that individuals with diabetes who also have cardiovascular disease may be susceptible to the short-term effects of air pollution.

Aged↗

PubMed2003

Occupational exposures to extremely low frequency magnetic fields and postmenopausal breast cancer.

BACKGROUND: The association between occupational exposure to extremely low frequency magnetic fields (ELF-MF) and risk of postmenopausal breast cancer was assessed in a case-control study. METHODS: Breast cancer cases were compared to cancer controls. Interviewers elicited information on risk factors and on lifetime work history. Industrial hygienists assigned to each job average duration of exposure to ELF-MF at four levels of intensities ("none," <0.2 microT; "low," 0.2-<0.5microT; "medium," 0.5-<1microT; "high," > or =1-10microT). Unconditional logistic regression was used to estimate adjusted odds ratios (OR) and 95% confidence intervals (95% CI). RESULTS: A total number of 608 cases and 667 controls participated. Adjusting for accepted breast cancer risk factors, we found an OR of 1.13 for lifetime occupational exposure to ELF-MF at medium or high intensities. Risks were larger for exposures before age 35 (OR = 1.40), and statistically significant for exposures before 35 among cases with progesterone receptor positive tumors (OR = 1.56, 95% CI=1.02-2.39). CONCLUSIONS: There appears to be a small increased risk for breast cancer among postmenopausal women exposed occupationally to ELF-MF.

Aged↗

PubMed2003

Associations between ambient air pollution and daily mortality among persons with congestive heart failure.

We conducted a mortality time series study to investigate the association between daily mortality for congestive heart failure (CHF), and daily concentrations of particles and gaseous pollutants in the ambient air of Montreal, Quebec, during the period 1984-1993. In addition, using data from the universal Quebec Health Insurance Plan, we identified individuals >/=65 years of age who, one year before death, had a diagnosis of CHF. Fixed-site air pollution monitors in Montreal provided daily mean levels of pollutants. We regressed the logarithm of daily counts of mortality on the daily mean levels of each pollutant, after accounting for seasonal and subseasonal fluctuations in the mortality time series, non-Poisson dispersion, weather variables, and other gaseous and particle pollutants. Using cause of death information, we did not find any associations between daily mortality for CHF and any air pollutants. The analyses of CHF defined from the medical record showed positive associations with coefficient of haze, the extinction coefficient, SO(2), and NO(2). For example, the mean percent increase in daily mortality for an increase in the coefficient of haze across the interquartile range was 4.32% (95% CI: 0.95-7.80%) and for NO(2) it was 4.08% (95% CI: 0.59-7.68%). These effects were generally higher in the warm season.

Aged↗

PubMed2002

Association between alcohol consumption and postmenopausal breast cancer: results of a case-control study in Montreal, Quebec, Canada.

OBJECTIVES: To determine the association between postmenopausal breast cancer and prior consumption of alcoholic beverages. METHODS: This case-control study, conducted in all Montreal hospitals between 1996 and 1997, included 556 postmenopausal women (age 50-75 years) who had a new histologically confirmed diagnosis of primary, malignant breast cancer. Control subjects (577) were selected from other histologically confirmed sites of cancer. A detailed history of alcohol consumption and other risk factors was obtained by interview. Indices reflecting alcohol consumption were developed and unconditional logistic regression was used to estimate adjusted odds ratios (OR) and 95% confidence intervals (CI). RESULTS: Current regular drinkers of any type of alcohol were at an increased risk of breast cancer (OR = 1.5; 95% CI 1.0-2.2). For all beverages considered, current regular drinkers showed higher risks than ever regular drinkers. The risk of breast cancer was highest among women who reported exclusive drinking of wine on a weekly or daily basis (e.g. current regular drinking: OR = 2.3; 95% CI 1.2-4.3). Women who started to drink wine on or before the age of 40 were at a 2.5 times increased risk (95% CI 1.4-4.4). CONCLUSIONS: Our findings provide further support for a positive association between the risk of postmenopausal breast cancer and alcohol consumption.

Aged↗