Biomedical subjects

N Kreiger

Publications and source records attributed to N Kreiger.

At least 19 recordsLinked to original sources

PubMed2006

Periodontal disease and perinatal outcomes: a case-control study.

AIM: Our aim was to measure the association of maternal periodontitis with low birth weight (LBW), pre-term LBW, and intra-uterine growth restriction. MATERIAL AND METHODS: An inclusive case-control design including subjects examined for periodontitis through attachment loss, information on perinatal outcomes and general health. Data were analysed through conditional logistic regression. RESULTS: Cases (n=304) and controls (n=611) had similar prevalence and severity of periodontitis, defined as at least three sites, in different teeth, with loss of three or more millimetres of clinical attachment level. Several factors were associated with the outcome, but the crude odds ratio for periodontitis was not significant. Odds ratio were 0.93 [95% confidence interval (CI): 0.63-1.41] for LBW and 0.92 (95% CI:0.54-1.57) for pre-term LBW in the presence of periodontitis, after adjustment for maternal age, previous pregnancies, pre-natal care, smoking, previous low birth or premature birth and other medical conditions, on a hierarchical model. CONCLUSIONS: Results do not support the hypothesis of association observed in previous studies after appropriate controlling for confounding variables. Negative peri-natal outcomes are better explained by determinants other than periodontal health. This study adds to the growing body of literature on the relationship between periodontal diseases and systemic health.

Birth Weight↗

PubMed2006

The effect of cyclooxygenase-2 inhibitors on bone mineral density: results from the Canadian Multicentre Osteoporosis Study.

INTRODUCTION: The use of cyclooxygenase-2 (COX-2) inhibitors has been demonstrated to not only impair load-induced bone formation but also prevent menopause-associated bone loss. We hypothesized that COX-2 inhibitor use would be associated with increased bone mineral density (BMD) in postmenopausal women not using estrogen therapy and, conversely, with decreased BMD in men. METHODS: The Canadian Multicentre Osteoporosis Study is a longitudinal, randomly selected, population-based community cohort. We present data from men (n=2,004) and postmenopausal women age 65 and older (n=2,776) who underwent a BMD measurement and structured interview in the 5th year of the study. The outcome measure was percent difference in BMD (g/cm(2)). RESULTS: Daily COX-2 inhibitor use was reported by 394 subjects. In men, daily use of COX-2 inhibitors was associated with a lower BMD at all hip sites, with a percent difference of -3.1% [95% confidence interval (CI), -6.0, -0.3] between users and nonusers at total hip. In postmenopausal women not using estrogen replacement therapy, daily COX-2 inhibitor use was associated with higher BMD at most sites [percent difference at total hip: +3.0% (95% CI, 0.3, 5.8)]. These effects appeared to be dose-dependent. CONCLUSION: COX-2 inhibitor use was associated with a lower BMD in men and, on the other hand, with a higher BMD in postmenopausal women not using estrogen replacement therapy. Men who have used COX-2 inhibitors may wish to seek BMD measurement to assess their fracture risk. However, COX-2 inhibitors may have utility in postmenopausal women if bone-selective analogs can be developed.

Acetaminophen↗

PubMed2001

Oral contraceptive use and bone mineral density in premenopausal women: cross-sectional, population-based data from the Canadian Multicentre Osteoporosis Study.

BACKGROUND: Positive and negative effects on bone mineral density (BMD) have been described as a result of the premenopausal use of oral contraceptives (OCs); increased fracture rates have also been reported. This study assessed the relation between OC use and BMD in a population-based, 9-centre, national sample of women aged 25-45 years. METHODS: Premenopausal women who had been enrolled in the Canadian Multicentre Osteoporosis Study were classified as having ever been OC users (> or = 3 months) or as having never been OC users (0 to < 3 months). Data were obtained through extensive questionnaires and measuring of participants' weight, height and the BMD of lumbar vertebrae and the proximal femur. RESULTS: Of the sample of 524 women, whose mean age was 36.3 (standard deviation [SD] 5.9) years, 454 had used OCs; their mean age when they started using OCs was 19.8 (SD 3.5) years and the mean duration of use was 6.8 (SD 4.8) years. Women who had ever and those who had never used OCs showed no differences in age, age at menarche, parity, current calcium intake, exercise, body mass index (BMI), education, past irregular cycles or amenorrhea. OC users reported more alcohol and cigarette use and more use of medications to create regular cycles. Mean BMD values (adjusted for age, BMI and height) were 0.02-0.04 g/cm2 (that is, 2.3%-3.7%) lower in OC users, and were significantly lower in the spine and trochanter. The BMD of the spine in OC users was 1.03 (SD 0.12) g/cm2 versus 1.07 (SD 0.12) g/cm2 (95% confidence interval [CI] of difference -0.07 to -0.001) in those who had never used OCs. BMD was neither related to the duration of OC use nor to gynecological age at first use. Current and past users had similar BMD values. INTERPRETATION: National, population-based data show lower BMD values for the trochanter and spine in premenopausal women who have used OCs compared with those who have never used OCs.

Absorptiometry, Photon↗

PubMed2001

Misclassification of exposure: coffee as a surrogate for caffeine intake.

This study was conducted to assess the effect of exposure misclassification when coffee is used as a surrogate measure of caffeine exposure. Subjects were randomly selected from the telephone directories of four regional municipalities in southern Ontario, CANADA: Data on daily caffeine intake from foods, beverages, and medications were collected from June to November 1995 through self-administered, mailed questionnaires from 481 men and women aged 30-75 years. Although coffee was the main source of caffeine, cross-tabulations of exposure to coffee by total caffeine intake showed that assessment of coffee alone severely underestimated caffeine intake by at least one exposure level. A hypothetical 10-fold increase in risk was completely obscured when only coffee was used to estimate total caffeine intake. The results of this study suggest that measuring coffee instead of caffeine intake may contribute to a lack of positive findings in studies of coffee as a risk factor for disease occurrence, if in fact caffeine is the exposure of interest. On the other hand, measurement of coffee, tea, and cola soft drink intake in the present study appeared to approximate caffeine intake sufficiently and not affect risk estimates adversely.

Adult↗

PubMed2001

A qualitative study of subject recruitment for familial cancer research.

PURPOSE: Familial epidemiological studies of cancer raise familiar ethical issues relating to informed consent and recruitment of participants. When the family is the unit of study, however, additional complexity arises. Educating and recruiting participants must be tailored to the relatives', as well as the proband's needs. An understanding of the prospective participants' concerns will aid the development of strategies for recruitment and will facilitate informed and voluntary consent. In the present study, qualitative methods were used to investigate these issues. METHODS: Focus groups with cancer patients, relatives of cancer patients, and individuals from the general population were separately conducted to identify issues that concern people who are asked to participate in family studies. RESULTS: Many of the issues which arose in the course of the focus group discussions were similar to those in any study. Yet, some of the themes emerging from the discussions were specific to familial research. In particular, participants expressed that the study should be endorsed by a trusted and familiar source; group discussions might facilitate the consent process; the benefit of the research should be clear and personal, as well as benefit the participants' family members; risks of participation should be explicit (e.g., insurance discrimination); and education about the disease and its familial nature would maintain commitment to the study. Finally, participants expressed concerns about being approached by programs to facilitate the identification and recruitment of other family members for research on family health issues. CONCLUSIONS: Findings from this study will aid future familial studies in developing a protocol that both adequately informs potential participants of the nature of familial research and maximize participation.

Adult↗

PubMed2001

Hormonal factors and pancreatic cancer in women.

PURPOSE: The aim of the study was to evaluate hormonal risk factors for carcinoma of the exocrine pancreas among postmenopausal women. METHODS: Mailed questionnaire data from 52 cases and 233 population-based controls in Ontario were used to assess parity, age at first birth, and other hormonal factors on pancreatic cancer risk. RESULTS: Reduced risk was seen with three or more pregnancies [adjusted odds ratio (OR) = 0.22, 95% confidence interval (CI) = 0.07-0.65] and use of oral contraceptives (adjusted OR = 0.36, 95% CI = 0.13-0.96), whereas no significant associations were found for age at menarche or menopause, or estrogen replacement therapy. Among parous women, later age at first full-term pregnancy significantly increased the risk of this cancer (adjusted OR = 4.05, 95% CI = 1.50-10.92 for ages 25-29 years, adjusted OR = 3.78, 95% CI = 1.02-14.06 for ages 30+ years). CONCLUSIONS: Our data support the hypothesis that pancreatic cancer is, at least in part, an estrogen-dependent disease; there is growing epidemiological evidence that aspects of reproductive history and hormonal exposure are associated with risk of this disease.

Adolescent↗

PubMed2001

Nonsteroidal anti-inflammatory drug use and breast cancer risk.

Findings from previous epidemiological studies are inconclusive, though they suggest nonsteroidal anti-inflammatory drug (NSAID) use is associated with a reduction in breast cancer risk. In addition, animal studies report that NSAIDs inhibit mammary tumor development. The association between NSAID use and breast cancer risk was evaluated using a case-control study design. Cases were a random sample of women diagnosed with a first primary cancer of the breast, aged 25-74 years, identified through the Ontario Cancer Registry, and diagnosed between July 1996 and September 1998. Controls were an age-matched random sample of the female population of Ontario. Cases (n = 3133) and controls (n = 3062) completed a mailed questionnaire with information on their past use of NSAID and other medications, as well as many risk factors thought to be associated with breast cancer. Multivariate logistic regression analysis was used to obtain adjusted odds ratio (OR) estimates. Use of any NSAID medication (daily use for > or =2 months) was found to be associated with a significant 24% reduction in breast cancer risk (OR = 0.76; 95% confidence interval: 0.66, 0.88). The reduced risk was strongest for use lasting > 8 years, compared with nonusers (OR = 0.68; 95% confidence interval: 0.54, 0.86). No marked trends were observed for time since first use or last use or age at first use. Our results suggest a reduction in breast cancer risk associated with any regular NSAID use. NSAID use is a modifiable factor, and any protective effect attributed to its use could be of great public health importance.

Adult↗

PubMed2000

Pre-natal and peri-natal exposures and risk of testicular germ-cell cancer.

The present case-control study was undertaken to investigate the association between exposure to maternal hormones and risk of testicular germ-cell cancer by histologic subgroups. Cases were males, aged 16 to 59 years, diagnosed with testicular germ-cell cancer in Ontario between 1987 and 1989. Histologic review was performed on all eligible cases for the purpose of categorizing cases as seminoma or non-seminoma (the latter classified 2 ways, with and without tumors containing seminoma). Risk factor data were collected on 502 cases, 346 case mothers, 975 age-matched controls, and 522 control mothers. Exogenous hormone exposure was associated with elevated risk (OR = 4.9, 95% CI 1.7-13.9). Several additional risk factors were associated with risk of testicular cancer: bleeding and threatened miscarriage (OR = 0.6, 95% CI 0.3-1.0), maternal cigarette smoking (12+ cigarettes/day OR = 0.6, 95% CI 0. 4-1.0). pre-term birth (OR = 1.6, 95% CI 1.0-2.5), and treatment for undescended testicle (OR = 8.0, 95% CI 3.2-20.0). First births were associated with elevated risk (OR = 1.7, 95% CI 1.0-2.8) among mothers below the age of 24 years at conception. There was little evidence that risk factors differed by histologic subgroup. We found evidence that exposure to maternal hormones, particularly estrogens, is associated with testicular germ-cell cancer risk. Not only does exposure to elevated levels (exogenous hormone use, pre-term birth, and first births among young mothers) increase risk but also exposure to relatively lower levels (heavy cigarette consumption and, perhaps, bleeding and threatened miscarriage) may decrease cancer risk.

Abortion, Threatened↗

PubMed2000

Antidepressant medication use and breast cancer risk.

Experimental and epidemiologic studies suggest that antidepressant medication use may be associated with breast cancer risk. This hypothesis was investigated using a population-based case-control study; cases diagnosed in 1995-1996 were identified using the Ontario Cancer Registry, and controls were randomly sampled from an Ontario Ministry of Finance database. Data were collected using a self-administered questionnaire, and multivariate logistic regression was used to estimate odds ratios and 95% confidence intervals. Adjusted odds ratio estimates ranged from 0.7 to 0.8 and were not statistically significant for "ever" use of antidepressants, tricyclics, and selective serotonin reuptake inhibitors. Compared with no antidepressant use, use of tricyclic antidepressants for greater than 2 years' duration was associated with an elevated risk of breast cancer (odds ratio (OR) = 2.1, 95% confidence interval (CI): 0.9, 5.0). Of the six most commonly reported antidepressant medications, only paroxetine use was associated with an increase in breast cancer risk (OR = 7.2, 95% CI: 0.9, 58.3). Results from this study do not support the hypothesis that "ever" use of any antidepressant medications is associated with breast cancer risk. Use of tricyclic medications for greater than 2 years, however, may be associated with a twofold elevation, and use of paroxetine may be associated with a substantial increase in breast cancer risk.

Adult↗

PubMed2000

Development and validation of the Osteoporosis Risk Assessment Instrument to facilitate selection of women for bone densitometry.

BACKGROUND: Although mass screening for osteoporosis is not recommended among postmenopausal women, there is no consensus on which women should undergo testing for low bone mineral density. The objective of this study was to develop and validate a clinical tool to help clinicians identify which women are at increased risk for osteoporosis and should therefore undergo further testing with bone densitometry. METHODS: Using Ontario baseline data from the Canadian Multicentre Osteoporosis Study, we identified all cognitively normal women aged 45 years or more who had undergone testing with dual-energy x-ray absorptiometry (DXA) at both the femoral neck and the lumbar spine (L1-L4). Participants who had a previous diagnosis of osteoporosis or were taking bone active medication other than ovarian hormones were excluded. The main outcome measure was low bone mineral density (T score of 2 or more standard deviations below the mean for young Canadian women) at either the femoral neck or the lumbar spine. Logistic regression analysis and receiver operating characteristic (ROC) analysis were used to identify the simplest algorithm that would identify women at increased risk for low bone mineral density. RESULTS: The study population comprised 1376 women, of whom 926 were allocated to the development of the tool and 450 to its validation. A simple algorithm based on age, weight and current estrogen use (yes or no) was developed. Validation of this 3-item Osteoporosis Risk Assessment Instrument (ORAI) showed that the tool had a sensitivity of 93.3% (95% confidence interval [CI] 86.3%-97.0%) and a specificity of 46.4% (95% CI 41.0%-51.8%) for selecting women with low bone mineral density. The sensitivity of the instrument for selecting women with osteoporosis was 94.4% (95% CI 83.7%-98.6%). Use of the ORAI represented a 38.7% reduction in DXA testing compared with screening all women in our study. INTERPRETATION: The ORAI accurately identifies the vast majority of women likely to have low bone mineral density and is effective in substantially decreasing the need for all women to undergo DXA testing.

Absorptiometry, Photon↗

PubMed2000

Relation of physical activity to risk of testicular cancer.

In North America and most Western European countries, testicular cancer is often cited as the most common cancer among young and middle-aged men, and yet few studies have examined the relation between modifiable factors and testicular cancer risk. Data collected between 1995 and 1996 in Ontario, Canada, as part of the Enhanced Cancer Surveillance Study were used to examine the relation between the frequency of recreational, and intensity of occupational, physical activity at various life periods, including cumulative and averaged lifetime activity and risk of testicular cancer. Analysis of 212 cases and 251 controls revealed that relatively high frequency of participation in moderate and strenuous recreational activity in the midteens may have an adverse effect on risk of testicular cancer (odds ratio = 2.36, 95% confidence interval: 1.20, 4.64 for moderate activity of greater than five times a week compared with three times or less a month and odds ratio = 2.58, 95% confidence interval: 1.14, 5.85 for strenuous activity of greater than five times a week compared with less than once a month). Moderate or strenuous occupational demands in one's 20s also increased risk of disease.

Adult↗

PubMed2000

Estimation of the prevalence of low bone density in Canadian women and men using a population-specific DXA reference standard: the Canadian Multicentre Osteoporosis Study (CaMos).

The Canadian Multicentre Osteoporosis Study (CaMos) is a prospective cohort study which will measure the incidence and prevalence of osteoporosis and fractures, and the effect of putative risk factors, in a random sample of 10,061 women and men aged > or = 25 years recruited in approximately equal numbers in nine centers across Canada. In this paper we report the results of studies to establish peak bone mass (PBM) which would be appropriate reference data for use in Canada. These reference data are used to estimate the prevalence of osteoporosis and osteopenia in Canadian women and men aged > or = 50 years. Participants were recruited via randomly selected household telephone listings. Bone mineral density (BMD) of the lumbar spine and femoral neck were measured by dual-energy X-ray absorptiometry using Hologic QDR 1000 or 2000 or Lunar DPX densitometers. BMD results for lumbar spine and femoral neck were converted to a Hologic base. BMD of the lumbar spine in 578 women and 467 men was constant to age 39 years giving a PBM of 1.042 +/- 0.121 g/cm2 for women and 1.058 +/- 0.127 g/cm2 for men. BMD at the femoral neck declined from age 29 years. The mean femoral neck BMD between 25 and 29 years was taken as PBM and was found to be 0.857 +/- 0.125 g/cm2 for women and 0.910 +/- 0.125 g/cm2 for men. Prevalence of osteoporosis, as defined by WHO criteria, in Canadian women aged > or = 50 years was 12.1% at the lumbar spine and 7.9% at the femoral neck with a combined prevalence of 15.8%. In men it was 2.9% at the lumbar spine and 4.8% at the femoral neck with a combined prevalence of 6.6%.

Absorptiometry, Photon↗

PubMed2000

Cigarette smoking and the risk of thyroid cancer.

Thyroid cancer, whose aetiology is largely uncertain, has been negatively associated with cigarette smoking in a number of studies, possibly consistent with the greater occurrence of the disease in women than in men. This association was explored in the context of a Canadian case-control study of thyroid cancer. Newly diagnosed cases were identified primarily through provincial cancer registries in Canada and controls were identified from the general population. Data were collected through mailed questionnaires, yielding 1224 cases and 2659 controls. Reduced risk was observed for ever/never cigarette smoking (risk ratio estimate (RR) of 0.71 (95% confidence interval (CI)=0.60-0.83) for females and 0.77 (95% CI=0.58-1.02)) for males. Dose-response effects were observed with duration, quantity smoked and pack-years of exposure, although there was no decreasing protective effect with the age started smoking or years since stopped smoking. There is evidence of reduced risk for all histological subgroups. The protective effect of smoking may be due to a number of different mechanisms, including an effect on thyroid stimulating hormone and on oestrogen metabolism.

Adolescent↗

PubMed2000

Effects on subject response of information brochures and small cash incentives in a mail-based case-control study.

PURPOSE: To investigate the impact on subject response of an information brochure and cash incentives included with mailed questionnaires in case-control studies. METHODS: A randomized trial was carried out within a case-control study investigating cancer in the Province of Ontario. Brochures were included with half of the mailed questionnaires sent to 7487 cases and 2561 controls. Controls were also sent cash incentives of $2, $5, or no money. RESULTS: With the brochure, response changed from 75.0% to 75.8% in cases, and from 70.3% to 71.1% in controls. Adjusting for differences in age, residence, sex, and cancer site/status, the change was 0.2% [95% confidence interval (CI) = -1.7-2.1] in cases, and 0.6% (95% CI = -3.1-4.3) in controls. The $2 and $5 incentives increased overall response in controls from 61.9% to 72.8% and 77.2%, respectively, i.e., by 10.9% (95% CI = 6.1-15.6) and 15.1% (95% CI = 10.4-19.7), after adjustment. This effect was largely confined to urban areas (for $2 and $5, respectively: 5.5% and 14.2% in Toronto, 15.3% and 20.4% in other urban areas vs. 2.7% and 1.0% in rural areas; p = 0.02). Response time showed little or no improvement when the brochure was included, but was markedly reduced for both the $2 and $5 incentives. CONCLUSIONS: Cash incentives can improve subject response in epidemiologic studies, whereas information brochures do not appear to have an effect.

Adult↗

PubMed2000

Is occupation a risk factor for thyroid cancer? Canadian Cancer Registries Epidemiology Research Group.

A Canadian case-control study explored the etiology of thyroid cancer, including occupational exposure. Analysis of job history from 1272 thyroid cancer patients and 2666 controls revealed statistically significant risks among the following occupations: Wood Processing, Pulp and Papermaking (odds ratio [OR] = 2.54, 95% confidence interval [CI] = 1.11-5.83); Sales and Service (OR = 1.26, 95% CI = 1.05-1.52); and Clerical (OR = 0.81, 95% CI = 0.67-0.97). ORs were adjusted for age, sex, province, cigarette smoking, education, self-reported exposure to radiation at work, and duration of employment. Exposure to ionizing radiation or electromagnetic fields at work (inferred from job histories) did not affect risk, nor did socioeconomic status, measured by education, income, or occupational prestige. Possible explanations for the results and further investigations are discussed.

Adult↗

PubMed2000

Impact of noninvasive imaging on increased incidental detection of renal cell carcinoma.

OBJECTIVE: To determine the impact of non-invasive imaging, specifically ultrasound imaging and computed tomography, on the incidental detection of renal cell carcinoma during two consecutive time periods, one prior and one subsequent to the acquisition of imaging equipment. METHODS: All located patient charts (83% of 207) of renal cell carcinoma cases (n = 172) were reviewed, and categorized by presentation method as 'incidental' or 'nonincidental' cases, based on defined criteria. Clinical information was recorded, cases were staged, and survival estimates were calculated. RESULTS: More than a third of the 172 cases were categorized as incidentally detected, most of which (82.5%) were detected during the latter time period. Either ultrasound or CT imaging was credited with detecting over 80% of the incidentally detected tumors. CONCLUSION: Ultrasound and CT imaging have contributed to the incidental detection of renal cell carcinomas during the two time periods. Stage significantly predicted survival (p<0.001) in a Cox proportional hazard model that also controlled for presentation, sex, and age.

Carcinoma, Renal Cell↗

PubMed1999

The risk of breast cancer following reproductive surgery.

Alteration of exposure to ovarian hormones, by eliminating or impairing the function of one or both ovaries, may affect the risk of breast cancer. To assess the relationship between reproductive surgical procedures and breast cancer risk, we conducted a retrospective cohort study involving 524,709 Ontario women who underwent tubal ligation or other salpingectomy, hysterectomy and/or ovariectomy between 1979 and 1993. Data on type and year of surgery were obtained from hospital records and linked with breast cancer diagnoses recorded in the Ontario Cancer Registry. Observed breast cancers were compared with age- and calendar-period expected rates in Ontario. A decreased risk of breast cancer was observed among women who had undergone either hysterectomy (observed/expected [O/E] = 0.87, P < 0.001) or unilateral ovariectomy (O/E = 0.74, P < 0.001). Bilateral ovariectomy and tubal ligation were associated with reduced risk when the surgery occurred before the age of 45 years, and tubal ligation was protective if performed after the age of 54 years. There was no trend in risk with increasing follow-up. Our data support the hypothesis that reduced levels of endogenous oestrogen may be protective for breast cancer in women.

Adolescent↗

PubMed1999

Establishing research priorities in etiologic epidemiology.

PURPOSE: A major goal of epidemiology is to discover the causes of disease in populations. The aim of this study was to develop a method for establishing research priorities within this very broad area of scientific inquiry. METHODS: While the approach is applicable to many diseases, cancer was used here, in part because of its importance to both individuals and governments. Measures of disease were estimated from data in the Ontario Cancer Registry, and combined to yield a single assessment of impact for each cancer site. Measures of exposure prevalence were identified from recent population health surveys. Cross-classification by disease and exposure rankings yielded a matrix of scores of "relative importance" for each cancer-exposure combination. Onto this matrix was overlaid: 1) estimates of statistical power for examining each association; 2) biological plausibility of each association; and 3) strength of the epidemiological evidence supporting each association. RESULTS: The disease-exposure matrix, viewed in light of statistical power, biological plausibility, and current epidemiological evidence, yielded, in the examples shown, some potentially interesting yet understudied associations (e.g., non-Hodgkin lymphoma (NHL) and certain aspects of dietary intake). CONCLUSIONS: The associations identified within the research hierarchy suggest not only new avenues for etiologic research, but also priorities for research focus.

Environmental Exposure↗